Condensed Matter

14 pages, 329 KiB

Open AccessReview

The Ancient Romans’ Route to Charge Density Waves in Cuprates

by Sergio Caprara

Condens. Matter 2019, 4(2), 60; https://doi.org/10.3390/condmat4020060 - 25 Jun 2019

Cited by 11 | Viewed by 3049

An account is given of the main steps that led the research group in Rome, to which the author belongs, to the formulation of the charge-density-wave scenario for high-

T_{c}

superconducting cuprates. The early finding of the generic tendency of strongly correlated [...] Read more.

An account is given of the main steps that led the research group in Rome, to which the author belongs, to the formulation of the charge-density-wave scenario for high-

T_{c}

superconducting cuprates. The early finding of the generic tendency of strongly correlated electron systems with short range interactions to undergo electron phase separation was subsequently contrasted with the homogenizing effect of the long-range Coulomb interaction. The two effects can find a compromise in the formation of incommensurate charge density waves. These charge density waves are inherently dynamical and are overdamped as a consequence of the possibility to decay in electron-hole pairs, yet tend to maintain a (quantum) critical character, which is mirrored in their marked momentum and frequency dependence and in their strong variation with temperature and doping. These dynamical incommensurate charge density waves act as mediators of pairing lading to high-

T_{c}

superconductivity, and provide the scattering mechanism that produces the observed violation of the Fermi-liquid paradigm in the metallic phase. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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4 pages, 178 KiB

Open AccessEditorial

High Precision X-Ray Measurements

by Alessandro Scordo

Condens. Matter 2019, 4(2), 59; https://doi.org/10.3390/condmat4020059 - 25 Jun 2019

Cited by 4 | Viewed by 2263

Abstract

Since their discovery in 1895, the detection of X-rays has had a strong impact and various applications in several fields of science and human life [...] Full article

(This article belongs to the Special Issue High Precision X-Ray Measurements)

15 pages, 3541 KiB

Open AccessArticle

Efficient Spatial Sampling for AFM-Based Cancer Diagnostics: A Comparison between Neural Networks and Conventional Data Analysis

by Gabriele Ciasca, Alberto Mazzini, Tanya E. Sassun, Matteo Nardini, Eleonora Minelli, Massimiliano Papi, Valentina Palmieri and Marco de Spirito

Condens. Matter 2019, 4(2), 58; https://doi.org/10.3390/condmat4020058 - 21 Jun 2019

Cited by 16 | Viewed by 3541

Abstract

Atomic force microscopy (AFM) in spectroscopy mode receives a lot of attention because of its potential in distinguishing between healthy and cancer tissues. However, the AFM translational process in clinical practice is hindered by the fact that it is a time-consuming technique in [...] Read more.

Atomic force microscopy (AFM) in spectroscopy mode receives a lot of attention because of its potential in distinguishing between healthy and cancer tissues. However, the AFM translational process in clinical practice is hindered by the fact that it is a time-consuming technique in terms of measurement and analysis time. In this paper, we attempt to address both issues. We propose the use of neural networks for pattern recognition to automatically classify AFM force–distance (FD) curves, with the aim of avoiding curve-fitting with the Sneddon model or more complicated ones. We investigated the applicability of this method to the classification of brain cancer tissues. The performance of the classifier was evaluated with receiving operating characteristic (ROC) curves for the approach and retract curves separately and in combination with each other. Although more complex and comprehensive models are required to demonstrate the general applicability of the proposed approach, preliminary evidence is given for the accuracy of the results, and arguments are presented to support the possible applicability of neural networks to the classification of brain cancer tissues. Moreover, we propose a possible strategy to shorten measurement times based on the estimation of the minimum number of FD curves needed to classify a tissue with a confidence level of 0.005. Taken together, these results have the potential to stimulate the design of more effective protocols to reduce AFM measurement times and to get rid of curve-fitting, which is a complex and time-consuming issue that requires experienced staff with a strong data-analysis background. Full article

(This article belongs to the Special Issue Complex Nanoscale Geometry and Dynamics at the Frontier between Biology and Material Science)

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22 pages, 641 KiB

Open AccessArticle

Mechanism of High-Temperature Superconductivity in Correlated-Electron Systems

by Takashi Yanagisawa

Condens. Matter 2019, 4(2), 57; https://doi.org/10.3390/condmat4020057 - 19 Jun 2019

Cited by 12 | Viewed by 6598

Abstract

It is very important to elucidate the mechanism of superconductivity for achieving room temperature superconductivity. In the first half of this paper, we give a brief review on mechanisms of superconductivity in many-electron systems. We believe that high-temperature superconductivity may occur in a [...] Read more.

It is very important to elucidate the mechanism of superconductivity for achieving room temperature superconductivity. In the first half of this paper, we give a brief review on mechanisms of superconductivity in many-electron systems. We believe that high-temperature superconductivity may occur in a system with interaction of large-energy scale. Empirically, this is true for superconductors that have been found so far. In the second half of this paper, we discuss cuprate high-temperature superconductors. We argue that superconductivity of high temperature cuprates is induced by the strong on-site Coulomb interaction, that is, the origin of high-temperature superconductivity is the strong electron correlation. We show the results on the ground state of electronic models for high temperature cuprates on the basis of the optimization variational Monte Carlo method. A high-temperature superconducting phase will exist in the strongly correlated region. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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8 pages, 2851 KiB

Open AccessArticle

Memristive Properties of PANI-Polysterene/PVDF-TrFE Interface

by Artem V. Budaev, Roman N. Belenkov and Nikita A. Emelianov

Condens. Matter 2019, 4(2), 56; https://doi.org/10.3390/condmat4020056 - 19 Jun 2019

Cited by 6 | Viewed by 3678

Abstract

The article presents the results of an experimental study of the transport of charge carriers through semiconductor PANI-polystyrene/ ferroelectric PVDF-TrFE interface. Current-voltage characteristics of the structure under study have a typical form for memristors and may be explained by the movement of charge [...] Read more.

The article presents the results of an experimental study of the transport of charge carriers through semiconductor PANI-polystyrene/ ferroelectric PVDF-TrFE interface. Current-voltage characteristics of the structure under study have a typical form for memristors and may be explained by the movement of charge carriers in the internal switchable field of the crystal ferroelectric microregions located within a bulk volume of amorphous PVDF-TrFE matrix. This assumption is subject to XRD phase analysis, FTIR spectroscopy, and X-ray EDS microanalysis. A long-term (about 100 h) relaxation is detected for the resistance of the PANI-polysturene/PVDF-TrFE interface after the current-voltage characteristics measurement cycle that is associated with the processes of capture and release traps of charge carriers. Full article

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11 pages, 5900 KiB

Open AccessArticle

SAXS Analysis of Magnetic Field Influence on Magnetic Nanoparticle Clusters

by Fábio Luís de Oliveira Paula

Condens. Matter 2019, 4(2), 55; https://doi.org/10.3390/condmat4020055 - 18 Jun 2019

Cited by 13 | Viewed by 4093

Abstract

In this work, we investigated the local colloidal structure of ferrofluid, in the presence of the external magnetic field. The nanoparticles studied here are of the core-shell type, with the core formed by manganese ferrite and maghemite shell, and were synthesized by the [...] Read more.

In this work, we investigated the local colloidal structure of ferrofluid, in the presence of the external magnetic field. The nanoparticles studied here are of the core-shell type, with the core formed by manganese ferrite and maghemite shell, and were synthesized by the coprecipitation method in alkaline medium. Measures of Small Angle X-ray Scattering (SAXS) performed in the Brazilian Synchrotron Light Laboratory (LNLS) were used for the study of the local colloidal structure of ferrofluid, so it was possible to study two levels of structure, cluster and isolated particles, in the regimes with and without applied magnetic field. In the methodology used here there is a combination of the information obtained in the system with and without magnetic field application. In this way, it is possible to undertake a better investigation of the colloidal dispersion. The theoretical formalism used: (i) the unification equation proposed by Beaucage G.; (ii) the analysis of the radial distribution function

p (r)

and (iii) theoretical calculation of the radius of gyration as a function of the moment of inertia of the spherical of n-nanoparticles. Full article

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16 pages, 2232 KiB

Open AccessArticle

Evaluating Superconductors through Current Induced Depairing

by Milind N. Kunchur

Condens. Matter 2019, 4(2), 54; https://doi.org/10.3390/condmat4020054 - 17 Jun 2019

Cited by 4 | Viewed by 3290

Abstract

The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density j. The critical temperature

T_{c}

is one of the first parameters that is measured and in a certain way defines [...] Read more.

The phenomenon of superconductivity occurs in the phase space of three principal parameters: temperature T, magnetic field B, and current density j. The critical temperature

T_{c}

is one of the first parameters that is measured and in a certain way defines the superconductor. From the practical applications point of view, of equal importance is the upper critical magnetic field

B_{c 2}

and conventional critical current density

j_{c}

(above which the system begins to show resistance without entering the normal state). However, a seldom-measured parameter, the depairing current density

j_{d}

, holds the same fundamental importance as

T_{c}

and

B_{c 2}

, in that it defines a boundary between the superconducting and normal states. A study of

j_{d}

sheds unique light on other important characteristics of the superconducting state such as the superfluid density and the nature of the normal state below

T_{c}

, information that can play a key role in better understanding newly-discovered superconducting materials. From a measurement perspective, the extremely high values of

j_{d}

make it difficult to measure, which is the reason why it is seldom measured. Here, we will review the fundamentals of current-induced depairing and the fast-pulsed current technique that facilitates its measurement and discuss the results of its application to the topological-insulator/chalcogenide interfacial superconducting system. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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8 pages, 2653 KiB

Open AccessArticle

Understanding Phase Stability of Metallic 1T-MoS₂ Anodes for Sodium-Ion Batteries

by Christopher Lane, Daxian Cao, Hongyan Li, Yucong Jiao, Bernardo Barbiellini, Arun Bansil and Hongli Zhu

Condens. Matter 2019, 4(2), 53; https://doi.org/10.3390/condmat4020053 - 10 Jun 2019

Cited by 21 | Viewed by 5948

Abstract

We discuss metallic 1T-MoS₂ as an anode material for sodium-ion batteries (SIBs). In situ Raman is used to investigate the stability of metallic MoS₂ during the charging and discharging processes. Parallel first-principles computations are used to gain insight into the experimental [...] Read more.

We discuss metallic 1T-MoS₂ as an anode material for sodium-ion batteries (SIBs). In situ Raman is used to investigate the stability of metallic MoS₂ during the charging and discharging processes. Parallel first-principles computations are used to gain insight into the experimental observations, including the measured conductivities and the high capacity of the anode. Full article

(This article belongs to the Special Issue Rechargeable Batteries Studied Using Advanced Spectroscopic and Computational Techniques)

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8 pages, 627 KiB

Open AccessArticle

Scaling between Superfluid Density and T_c in Overdoped La_2−xSr_xCuO₄ Films

by Evandro V. L. de Mello

Condens. Matter 2019, 4(2), 52; https://doi.org/10.3390/condmat4020052 - 6 Jun 2019

Viewed by 2730

Abstract

We used an electronic phase separation approach to interpret the scaling between the low-temperature superfluid density average

ρ_{sc} (0)

and the superconducting critical temperature

T_{c}

on overdoped La

_{2 - x}

Sr

_{x}

CuO

_{4}

films. Guided by the [...] Read more.

We used an electronic phase separation approach to interpret the scaling between the low-temperature superfluid density average

ρ_{sc} (0)

and the superconducting critical temperature

T_{c}

on overdoped La

_{2 - x}

Sr

_{x}

CuO

_{4}

films. Guided by the observed nematic and incommensurate charge ordering (CO), we performed simulations with a free energy that reproduces charge domains with wavelength

λ_{C O}

and provides a scale to local superconducting interactions. Under these conditions a complex order parameter with amplitude

Δ_{d} (r_{i})

and phase

θ (r_{i})

may develop at a domain i. We assumed that these domains are coupled by Josephson energy

E_{J} (r_{i j})

, proportional to the local superfluid density

ρ_{sc} (r_{i j})

. Long-range order occured when the average

E_{J} (T_{c})

is

\sim k_{B} T_{c}

. The linear

ρ_{s c} (0)

vs.

T_{c}

relation was satisfied whenever CO was present, even with almost vanishing charge amplitudes. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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19 pages, 3341 KiB

Open AccessReview

Fermi-Bose Mixtures and BCS-BEC Crossover in High-T_c Superconductors

by Maxim Yu. Kagan and Antonio Bianconi

Condens. Matter 2019, 4(2), 51; https://doi.org/10.3390/condmat4020051 - 3 Jun 2019

Cited by 25 | Viewed by 4975

Abstract

In this review article we consider theoretically and give experimental support to the models of the Fermi-Bose mixtures and the BCS-BEC (Bardeen Cooper Schrieffer–Bose Einstein) crossover compared with the strong-coupling approach, which can serve as the cornerstones on the way from high-temperature to [...] Read more.

In this review article we consider theoretically and give experimental support to the models of the Fermi-Bose mixtures and the BCS-BEC (Bardeen Cooper Schrieffer–Bose Einstein) crossover compared with the strong-coupling approach, which can serve as the cornerstones on the way from high-temperature to room-temperature superconductivity in pressurized metallic hydrides. We discuss some key theoretical ideas and mechanisms proposed for unconventional superconductors (cuprates, pnictides, chalcogenides, bismuthates, diborides, heavy-fermions, organics, bilayer graphene, twisted graphene, oxide hetero-structures), superfluids and balanced or imbalanced ultracold Fermi gases in magnetic traps. We build a bridge between unconventional superconductors and recently discovered pressurized hydrides superconductors H₃S and LaH₁₀ with the critical temperature close to room temperature. We discuss systems with a line of nodal Dirac points close to the Fermi surface and superconducting shape resonances, and hyperbolic superconducting networks which are very important for the development of novel topological superconductors, for the energetics, for the applications in nano-electronics and quantum computations. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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7 pages, 254 KiB

Open AccessEditorial

Surface Plasmon Resonance (SPR) to Magneto-Optic SPR

by Conrad Rizal, Vladimir Belotelov, Daria Ignatyeva, Anatoly K. Zvezdin and Simone Pisana

Condens. Matter 2019, 4(2), 50; https://doi.org/10.3390/condmat4020050 - 27 May 2019

Cited by 23 | Viewed by 4995

Abstract

In this editorial, a brief background of the surface plasmon resonance (SPR) principle is discussed, followed by several aspects of magneto-optic SPR (MOSPR) and sensing schemes from the viewpoint of fundamental studies and potential technological applications. New sensitivity metrics are introduced that would [...] Read more.

In this editorial, a brief background of the surface plasmon resonance (SPR) principle is discussed, followed by several aspects of magneto-optic SPR (MOSPR) and sensing schemes from the viewpoint of fundamental studies and potential technological applications. New sensitivity metrics are introduced that would allow researchers to compare the performance of SPR and MOSPR-based sensors. Merits of MOSPR over SPR based sensors and challenges faced by MOSPR sensors in terms of their practical use and portability are also considered. The editorial ends with potential new configurations and future prospects. This work is considered highly significant to device engineers, graduate and undergraduate students, and researchers of all levels involved in developing new classes of bio-devices for sensing, imaging, environmental monitoring, toxic gas detection, and surveying applications to name a few. Full article

(This article belongs to the Special Issue Magnetoplamonics Material and Devices)

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11 pages, 1862 KiB

Open AccessArticle

Improved Transition Metal Dichalcogenides-Based Surface Plasmon Resonance Biosensors

by Mohammad Hasibul Hasan Hasib, Jannati Nabiha Nur, Conrad Rizal and Kamrun Nahar Shushama

Condens. Matter 2019, 4(2), 49; https://doi.org/10.3390/condmat4020049 - 22 May 2019

Cited by 39 | Viewed by 4403

Abstract

Surface plasmon resonance (SPR) biosensors based on transition metal dichalcogenides (TMDC) materials have shown improved performance in terms of sensitivity, detection accuracy (DA), and quality factor (QF) over conventional biosensors. In this paper, we propose a five-layers model containing black phosphorus (BP) and [...] Read more.

Surface plasmon resonance (SPR) biosensors based on transition metal dichalcogenides (TMDC) materials have shown improved performance in terms of sensitivity, detection accuracy (DA), and quality factor (QF) over conventional biosensors. In this paper, we propose a five-layers model containing black phosphorus (BP) and TMDC (Ag/BP/WS₂) in Kretschmann configuration. Using TM-polarized light at 633 nm, we numerically demonstrate the highest sensitivity (375°/RIU), DA (0.9210), and QF (65.78 1/RIU) reported so far over similar materials. Refractive index (RI) of the coupling prism has also played an essential role in enhancing the performance of these biosensors. The research on TMDC materials is still new, and these materials bring about opportunities to develop a new class of biosensor. Full article

(This article belongs to the Special Issue Magnetoplamonics Material and Devices)

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16 pages, 473 KiB

Open AccessArticle

On Quantum Extensions of Hydrodynamic Lattice Gas Automata

by Peter Love

Condens. Matter 2019, 4(2), 48; https://doi.org/10.3390/condmat4020048 - 11 May 2019

Cited by 2 | Viewed by 2889

Abstract

We consider quantum extensions of classical hydrodynamic lattice gas models. We find that the existence of local conserved quantities strongly constrains such extensions. We find the only extensions that retain local conserved quantities correspond to changing the local encoding of a subset of [...] Read more.

We consider quantum extensions of classical hydrodynamic lattice gas models. We find that the existence of local conserved quantities strongly constrains such extensions. We find the only extensions that retain local conserved quantities correspond to changing the local encoding of a subset of the bits. These models maintain separability of the state throughout the evolution and are thus efficiently classically simulable. We then consider evolution of these models in the case where any of the bits can be encoded and measured in one of two local bases. In the case that either encoding is allowed, the models are efficiently classically simulable. In the case that both encoding and measurement is allowed in either basis, we argue that efficient classical simulation is unlikely. In particular, for classical models that are computationally universal such quantum extensions can encode Simon’s algorithm, thus presenting an obstacle to efficient classical simulation. Full article

(This article belongs to the Special Issue Quantum Cellular Automata and Quantum Walks)

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19 pages, 417 KiB

Open AccessReview

Time Reversal Symmetry Breaking Superconductors: Sr₂RuO₄ and Beyond

by Karol Izydor Wysokiński

Condens. Matter 2019, 4(2), 47; https://doi.org/10.3390/condmat4020047 - 9 May 2019

Cited by 18 | Viewed by 4988

Abstract

Recent work done on the time reversal symmetry (TRS) breaking superconductors is reviewed in this paper. The special attention is paid to Sr

_{2}

RuO

_{4}

believed to be spin triplet chiral p-wave superconductor which break TRS and is expected to posses non-trivial [...] Read more.

Recent work done on the time reversal symmetry (TRS) breaking superconductors is reviewed in this paper. The special attention is paid to Sr

_{2}

RuO

_{4}

believed to be spin triplet chiral p-wave superconductor which break TRS and is expected to posses non-trivial topological properties. The family of TRS breaking superconductors is growing relatively fast, with many of its newly discovered members being non-centrosymmetric. However not only Sr

_{2}

RuO

_{4}

but also many other superconductors which possess center of inversion also break TRS. The TRS is often identified by means of the muon spin relaxation (

μ

SR) and the Kerr effect. Both methods effectively measure the appearance of the spontaneous bulk magnetic field below superconducting transition temperature. This compound provides an example of the material whose many band, multi-condensate modeling has enjoyed a number of successes, but the full understanding has not been achieved yet. We discuss in some details the properties of the material. Among them is the Kerr effect and by understanding has resulted in the discovery of the novel mechanism of the phenomenon. The mechanism is universal and thus applicable to all systems with multi-orbital character of states at the Fermi energy. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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16 pages, 1078 KiB

Open AccessReview

Orbital Symmetry and Orbital Excitations in High-T_c Superconductors

by Andrzej M. Oleś, Krzysztof Wohlfeld and Giniyat Khaliullin

Condens. Matter 2019, 4(2), 46; https://doi.org/10.3390/condmat4020046 - 6 May 2019

Cited by 11 | Viewed by 5208

Abstract

We discuss a few possibilities of high-

T_{c}

superconductivity with more than one orbital symmetry contributing to the pairing. First, we show that the high energies of orbital excitations in various cuprates suggest a simplified model with a single orbital of [...] Read more.

We discuss a few possibilities of high-

T_{c}

superconductivity with more than one orbital symmetry contributing to the pairing. First, we show that the high energies of orbital excitations in various cuprates suggest a simplified model with a single orbital of

x^{2} - y^{2}

symmetry doped by holes. Next, several routes towards involving both

e_{g}

orbital symmetries for doped holes are discussed: (i) some give superconductivity in a CuO

_{2}

monolayer on Bi2212 superconductors, Sr

_{2}

CuO

_{4 - δ}

, Ba

_{2}

CuO

_{4 - δ}

, while (ii) others as nickelate heterostructures or Eu

_{2 - x}

Sr

_{x}

NiO

_{4}

, could in principle realize it as well. At low electron filling of Ru ions, spin-orbital entangled states of

t_{2 g}

symmetry contribute in Sr

_{2}

RuO

_{4}

. Finally, electrons with both

t_{2 g}

and

e_{g}

orbital symmetries contribute to the superconducting properties and nematicity of Fe-based superconductors, pnictides or FeSe. Some of them provide examples of orbital-selective Cooper pairing. Full article

(This article belongs to the Special Issue From cuprates to Room Temperature Superconductors)

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7 pages, 1484 KiB

Open AccessArticle

High Precision Test of the Pauli Exclusion Principle for Electrons

by Kristian Piscicchia, Aidin Amirkhani, Sergio Bartalucci, Sergio Bertolucci, Massimiliano Bazzi, Mario Bragadireanu, Michael Cargnelli, Alberto Clozza, Catalina Curceanu, Raffaele Del Grande, Luca De Paolis, Jean-Pierre Egger, Carlo Fiorini, Carlo Guaraldo, Mihail Iliescu, Matthias Laubenstein, Johann Marton, Marco Miliucci, Edoardo Milotti, Andreas Pichler, Dorel Pietreanu, Alessandro Scordo, Hexi Shi, Diana Laura Sirghi, Florin Sirghi, Laura Sperandio, Oton Vazquez Doce and Johann Zmeskal Show full author list Hide full author list

Condens. Matter 2019, 4(2), 45; https://doi.org/10.3390/condmat4020045 - 2 May 2019

Cited by 3 | Viewed by 3442

Abstract

The VIP-2 experiment aims to perform high precision tests of the Pauli Exclusion Principle for electrons. The method consists in circulating a continuous current in a copper strip, searching for the X radiation emission due to a prohibited transition (from the 2p level [...] Read more.

The VIP-2 experiment aims to perform high precision tests of the Pauli Exclusion Principle for electrons. The method consists in circulating a continuous current in a copper strip, searching for the X radiation emission due to a prohibited transition (from the 2p level to the 1s level of copper when this is already occupied by two electrons). VIP already set the best limit on the PEP violation probability for electrons

\frac{1}{2} β^{2} < 4.7 \times 10^{- 29}

, the goal of the upgraded VIP-2 (VIolation of the Pauli Exclusion Principle-2) experiment is to improve this result of two orders of magnitude at least. The experimental apparatus and the results of the analysis of a first set of collected data will be presented. Full article

(This article belongs to the Special Issue High Precision X-Ray Measurements)

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45 pages, 1669 KiB

Open AccessArticle

Electrostatic Interaction of Point Charges in Three-Layer Structures: The Classical Model

by Alexander M. Gabovich and Alexander I. Voitenko

Condens. Matter 2019, 4(2), 44; https://doi.org/10.3390/condmat4020044 - 2 May 2019

Cited by 6 | Viewed by 4469

Abstract

Electrostatic interaction energy W between two point charges in a three-layer plane system was calculated on the basis of the Green’s function method in the classical model of constant dielectric permittivities for all media involved. A regular method for the calculation of [...] Read more.

Electrostatic interaction energy W between two point charges in a three-layer plane system was calculated on the basis of the Green’s function method in the classical model of constant dielectric permittivities for all media involved. A regular method for the calculation of

W (Z, Z^{'}, R)

, where Z and

Z^{'}

are the charge coordinates normal to the interfaces, and R the lateral (along the interfaces) distance between the charges, was proposed. The method consists in substituting the evaluation of integrals of rapidly oscillating functions over the semi-infinite interval by constructing an analytical series of inverse radical functions to a required accuracy. Simple finite-term analytical approximations of the dependence

W (Z, Z^{'}, R)

were proposed. Two especially important particular cases of charge configurations were analyzed in more detail: (i) both charges are in the same medium and

Z = Z^{'}

; and (ii) the charges are located at different interfaces across the slab. It was demonstrated that the W dependence on the charge–charge distance

S = \sqrt{R^{2} + {(Z - Z^{'})}^{2}}

differs from the classical Coulombic one

W \sim S^{- 1}

. This phenomenon occurs due to the appearance of polarization charges at both interfaces, which ascribes a many-body character to the problem from the outset. The results obtained testify, in particular, that the electron–hole interaction in heterostructures leading to the exciton formation is different in the intra-slab and across-slab charge configurations, which is usually overlooked in specific calculations related to the subject concerned. Our consideration clearly demonstrates the origin, the character, and the consequences of the actual difference. The often used Rytova–Keldysh approximation was analyzed. The cause of its relative success was explained, and the applicability limits were determined. Full article

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24 pages, 723 KiB

Open AccessArticle

Superconducting Properties of 3D Low-Density TI-Bipolaron Gas in Magnetic Field

by Victor D. Lakhno

Condens. Matter 2019, 4(2), 43; https://doi.org/10.3390/condmat4020043 - 25 Apr 2019

Cited by 8 | Viewed by 3163

Abstract

Consideration is given to thermodynamical properties of a three-dimensional Bose-condensate of translation-invariant bipolarons (TI-bipolarons) in magnetic field. The critical temperature of transition, critical magnetic fields, energy, heat capacity and the transition heat of TI-bipolaron gas are calculated. Such values as maximum magnetic field, [...] Read more.

Consideration is given to thermodynamical properties of a three-dimensional Bose-condensate of translation-invariant bipolarons (TI-bipolarons) in magnetic field. The critical temperature of transition, critical magnetic fields, energy, heat capacity and the transition heat of TI-bipolaron gas are calculated. Such values as maximum magnetic field, London penetration depth and their temperature dependencies are calculated. The results obtained are used to explain experiments on high-temperature superconductors. Full article

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14 pages, 6794 KiB

Open AccessArticle

X-ray Detectors for Kaonic Atoms Research at DAΦNE

by Catalina Curceanu, Aidin Amirkhani, Ata Baniahmad, Massimiliano Bazzi, Giovanni Bellotti, Carolina Berucci, Damir Bosnar, Mario Bragadireanu, Michael Cargnelli, Alberto Clozza, Raffaele Del Grande, Carlo Fiorini, Francesco Ghio, Carlo Guaraldo, Mihail Iliescu, Masaiko Iwasaki, Paolo Levi Sandri, Johann Marton, Marco Miliucci, Pavel Moskal, Szymon Niedźwiecki, Shinji Okada, Dorel Pietreanu, Kristian Piscicchia, Alessandro Scordo, Hexi Shi, Michal Silarski, Diana Sirghi, Florin Sirghi, Magdalena Skurzok, Antonio Spallone, Hideyuki Tatsuno, Oton Vazquez Doce, Eberhard Widmann and Johann Zmeskal Show full author list Hide full author list

Condens. Matter 2019, 4(2), 42; https://doi.org/10.3390/condmat4020042 - 25 Apr 2019

Cited by 3 | Viewed by 3943

Abstract

This article presents the kaonic atom studies performed at the INFN National Laboratory of Frascati (Laboratori Nazionali di Frascati dell’INFN, LNF-INFN) since the opening of this field of research at the DA

Φ

NE collider in early 2000. Significant achievements have been obtained [...] Read more.

This article presents the kaonic atom studies performed at the INFN National Laboratory of Frascati (Laboratori Nazionali di Frascati dell’INFN, LNF-INFN) since the opening of this field of research at the DA

Φ

NE collider in early 2000. Significant achievements have been obtained by the DA

Φ

NE Exotic Atom Research (DEAR) and Silicon Drift Detector for Hadronic Atom Research by Timing Applications (SIDDHARTA) experiments on kaonic hydrogen, which have required the development of novel X-ray detectors. The 2019 installation of the new SIDDHARTA-2 experiment to measure kaonic deuterium for the first time has been made possible by further technological advances in X-ray detection. Full article

(This article belongs to the Special Issue High Precision X-Ray Measurements)

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7 pages, 2499 KiB

Open AccessArticle

Structural Evolution of MoO₃ Thin Films Deposited on Copper Substrates upon Annealing: An X-ray Absorption Spectroscopy Study

by Salvatore Macis, Javad Rezvani, Ivan Davoli, Giannantonio Cibin, Bruno Spataro, Jessica Scifo, Luigi Faillace and Augusto Marcelli

Condens. Matter 2019, 4(2), 41; https://doi.org/10.3390/condmat4020041 - 18 Apr 2019

Cited by 21 | Viewed by 4216

Abstract

Structural changes of MoO₃ thin films deposited on thick copper substrates upon annealing at different temperatures were investigated via ex situ X-Ray Absorption Spectroscopy (XAS). From the analysis of the X-ray Absorption Near-Edge Structure (XANES) pre-edge and Extended X-ray Absorption Fine Structure [...] Read more.

Structural changes of MoO₃ thin films deposited on thick copper substrates upon annealing at different temperatures were investigated via ex situ X-Ray Absorption Spectroscopy (XAS). From the analysis of the X-ray Absorption Near-Edge Structure (XANES) pre-edge and Extended X-ray Absorption Fine Structure (EXAFS), we show the dynamics of the structural order and of the valence state. As-deposited films were mainly disordered, and ordering phenomena did not occur for annealing temperatures up to 300 °C. At ~350 °C, a dominant α-MoO₃ crystalline phase started to emerge, and XAS spectra ruled out the formation of a molybdenum dioxide phase. A further increase of the annealing temperature to ~500 °C resulted in a complex phase transformation with a concurrent reduction of Mo⁶⁺ ions to Mo⁴⁺. These original results suggest the possibility of using MoO₃ as a hard, protective, transparent, and conductive material in different technologies, such as accelerating copper-based devices, to reduce damage at high gradients. Full article

(This article belongs to the Special Issue High Precision X-Ray Measurements)

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16 pages, 301 KiB

Open AccessArticle

Discrete Geometry from Quantum Walks

by Fabrice Debbasch

Condens. Matter 2019, 4(2), 40; https://doi.org/10.3390/condmat4020040 - 11 Apr 2019

Cited by 11 | Viewed by 2739

Abstract

A particular family of Discrete Time Quantum Walks (DTQWs) simulating fermion propagation in 2D curved space-time is revisited. Usual continuous covariant derivatives and spin-connections are generalized into discrete covariant derivatives along the lattice coordinates and discrete connections. The concepts of metrics and 2-beins [...] Read more.

A particular family of Discrete Time Quantum Walks (DTQWs) simulating fermion propagation in 2D curved space-time is revisited. Usual continuous covariant derivatives and spin-connections are generalized into discrete covariant derivatives along the lattice coordinates and discrete connections. The concepts of metrics and 2-beins are also extended to the discrete realm. Two slightly different Riemann curvatures are then defined on the space-time lattice as the curvatures of the discrete spin connection. These two curvatures are closely related and one of them tends at the continuous limit towards the usual, continuous Riemann curvature. A simple example is also worked out in full. Full article

(This article belongs to the Special Issue Quantum Cellular Automata and Quantum Walks)

12 pages, 341 KiB

Open AccessArticle

Quantized Alternate Current on Curved Graphene

by Kyriakos Flouris, Sauro Succi and Hans J. Herrmann

Condens. Matter 2019, 4(2), 39; https://doi.org/10.3390/condmat4020039 - 9 Apr 2019

Cited by 3 | Viewed by 3164

Abstract

Based on the numerical solution of the Quantum Lattice Boltzmann Method in curved space, we predicted the onset of a quantized alternating current on curved graphene sheets. This numerical prediction was verified analytically via a set of semi-classical equations that related the Berry [...] Read more.

Based on the numerical solution of the Quantum Lattice Boltzmann Method in curved space, we predicted the onset of a quantized alternating current on curved graphene sheets. This numerical prediction was verified analytically via a set of semi-classical equations that related the Berry curvature to real space curvature. The proposed quantized oscillating current on curved graphene could form the basis for the implementation of quantum information-processing algorithms. Full article

(This article belongs to the Special Issue Quantum Cellular Automata and Quantum Walks)

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14 pages, 794 KiB

Open AccessArticle

Pyrolitic Graphite Mosaic Crystal Thickness and Mosaicity Optimization for an Extended Source Von Hamos X-ray Spectrometer

by Alessandro Scordo, Catalina Curceanu, Marco Miliucci, Florin Sirghi and Johann Zmeskal

Condens. Matter 2019, 4(2), 38; https://doi.org/10.3390/condmat4020038 - 3 Apr 2019

Cited by 7 | Viewed by 3418

Abstract

Bragg spectroscopy, one of the best established experimental techniques for high energy resolution X-ray measurements, has always been limited to the measurement of photons produced from well collimated (tens of microns) or point-like sources; recently, the VOXES collaboration at INFN National Laboratories of [...] Read more.

Bragg spectroscopy, one of the best established experimental techniques for high energy resolution X-ray measurements, has always been limited to the measurement of photons produced from well collimated (tens of microns) or point-like sources; recently, the VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution and high precision X-ray spectrometer working also with extended isotropic sources. The realized spectrometer makes use of Highly Annealed Pyrolitic Graphite (HAPG) crystals in a “semi”-Von Hamos configuration, in which the position detector is rotated with respect to the standard Von Hamos one, to increase the dynamic energy range, and shows energy resolutions at the level of 0.1% for photon energies up to 10 keV and effective source sizes in the range 400–1200

μ

m in the dispersive plane. Such wide effective source dimensions are achieved using a double slit system to produce a virtual point-like source between the emitting target and the crystal. The spectrometer performances in terms of reflection efficiency and peak resolution depend on several parameters, among which a special role is played by the crystal mosaicity and thickness. In this work, we report the measurements of the Cu(K

_{α 1, 2}

) and the Fe(K

_{α 1, 2}

) lines performed with different mosaicity and thickness crystals in order to investigate the influence of the parameters on the peak resolution and on the reflection efficiency mentioned above. Full article

(This article belongs to the Special Issue High Precision X-Ray Measurements)

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10 pages, 1534 KiB

Open AccessArticle

Ab Initio Study of the Electronic, Vibrational, and Mechanical Properties of the Magnesium Diboride Monolayer

by Jelena Pešić, Igor Popov, Andrijana Šolajić, Vladimir Damljanović, Kurt Hingerl, Milivoj Belić and Radoš Gajić

Condens. Matter 2019, 4(2), 37; https://doi.org/10.3390/condmat4020037 - 2 Apr 2019

Cited by 8 | Viewed by 4551

Abstract

Magnesium diboride gained significant interest in the materials science community after the discovery of its superconductivity, with an unusually high critical temperature of 39 K. Many aspects of the electronic properties and superconductivity of bulk MgB

_{2}

and thin sheets of MgB [...] Read more.

Magnesium diboride gained significant interest in the materials science community after the discovery of its superconductivity, with an unusually high critical temperature of 39 K. Many aspects of the electronic properties and superconductivity of bulk MgB

_{2}

and thin sheets of MgB

_{2}

have been determined; however, a single layer of MgB

_{2}

has not yet been fully theoretically investigated. Here, we present a detailed study of the structural, electronic, vibrational, and elastic properties of monolayer MgB

_{2}

, based on ab initio methods. First-principles calculations reveal the importance of reduction of dimensionality on the properties of MgB

_{2}

and thoroughly describe the properties of this novel 2D material. The presence of a negative Poisson ratio, higher density of states at the Fermi level, and a good dynamic stability under strain make the MgB

_{2}

monolayer a prominent material, both for fundamental research and application studies. Full article

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14 pages, 3410 KiB

Open AccessArticle

Thermodynamic Stability, Thermoelectric, Elastic and Electronic Structure Properties of ScMN₂-Type (M = V, Nb, Ta) Phases Studied by ab initio Calculations

by Robert Pilemalm, Leonid Pourovskii, Igor Mosyagin, Sergei Simak and Per Eklund

Condens. Matter 2019, 4(2), 36; https://doi.org/10.3390/condmat4020036 - 29 Mar 2019

Cited by 5 | Viewed by 4648

Abstract

ScMN₂-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but they have up to now not been much studied. However, based on the properties of binary ScN and its [...] Read more.

ScMN₂-type (M = V, Nb, Ta) phases are layered materials that have been experimentally reported for M = Ta and Nb, but they have up to now not been much studied. However, based on the properties of binary ScN and its alloys, it is reasonable to expect these phases to be of relevance in a range of applications, including thermoelectrics. Here, we have used first-principles calculations to study their thermodynamic stability, elastic, thermoelectric and electronic properties. We have used density functional theory to calculate lattice parameters, the mixing enthalpy of formation and electronic density of states as well as the thermoelectric properties and elastic constants (c_ij), bulk (B), shear (G) and Young’s (E) modulus, which were compared with available experimental data. Our results indicate that the considered systems are thermodynamically and elastically stable and that all are semiconductors with small band gaps. All three materials display anisotropic thermoelectric properties and indicate the possibility to tune these properties by doping. In particular, ScVN₂, featuring the largest band gap exhibits a particularly large and strongly doping-sensitive Seebeck coefficient. Full article

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15 pages, 6847 KiB

Open AccessArticle

Observing Dynamical Systems Using Magneto-Controlled Diffraction

by Alberto Tufaile, Timm A. Vanderelli, Michael Snyder and Adriana Pedrosa Biscaia Tufaile

Condens. Matter 2019, 4(2), 35; https://doi.org/10.3390/condmat4020035 - 28 Mar 2019

Cited by 10 | Viewed by 7556

Abstract

Observing the light passing through a thin layer of ferrofluid, we can see the occurrence of interesting effects, both in the formation patterns within the ferrofluid layer and in the dispersion of light outside that layer. This leads us to ask what the [...] Read more.

Observing the light passing through a thin layer of ferrofluid, we can see the occurrence of interesting effects, both in the formation patterns within the ferrofluid layer and in the dispersion of light outside that layer. This leads us to ask what the explanations associated with these effects are. In this paper, we analyze and explain the occurrence of these luminous patterns using a Ferrolens, commercially known as a Ferrocell. We present details of our experimental apparatus, followed by a discussion of some properties of light polarization and its relation to the formation of magnetic contours produced by a Ferrolens. In addition, we present the observation of a magnetochiral effect in this system. Next, we propose an application of this experiment in dynamical systems. The dynamical system is the direct observation of diffracted lines in Ferrolens, a special case of a Hele-Shaw cell containing a transparent ferrofluid subjected to various light sources. Full article

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Condens. Matter, Volume 4, Issue 2 (June 2019) – 26 articles

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