Condensed Matter

11 pages, 1715 KiB

Open AccessArticle

Annealed Low Energy States in Frustrated Large Square Josephson Junction Arrays

by Martijn Lankhorst, Alexander Brinkman, Hans Hilgenkamp, Nicola Poccia and Alexander Golubov

Condens. Matter 2018, 3(2), 19; https://doi.org/10.3390/condmat3020019 - 13 Jun 2018

Cited by 6 | Viewed by 3722

Numerical simulations were done to find low energy states in frustrated large square Josephson Junction arrays in a perpendicular magnetic field using simulated annealing on the coupled RSJ model. These simulations were made possible by a new algorithm suitable for parallel gpu computing [...] Read more.

Numerical simulations were done to find low energy states in frustrated large square Josephson Junction arrays in a perpendicular magnetic field using simulated annealing on the coupled RSJ model. These simulations were made possible by a new algorithm suitable for parallel gpu computing and reduced complexity. Free boundary conditions were used so that values of the frustration factor f that are incommensurate with the array size are permitted. The resulting energy as a function of f is continuous with logarithmic discontinuities in the derivative

d E / d f

at rational frustration factors

f = p / q

with small q, substantiating the mathematical proof that this curve is continuous and further showing that the staircase state hypothesis is incorrect. The solution shows qualitative similarities with the lowest energy branch of the Hofstadter butterfly, which is a closely related problem. Furthermore, it is found that at the edge of an array there are either extra vortices or missing vortices depending the frustration factor, and the width of this region is independent of the array size. 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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20 pages, 1003 KiB

Open AccessArticle

Microscopic Linear Response Theory of Spin Relaxation and Relativistic Transport Phenomena in Graphene

by Manuel Offidani, Roberto Raimondi and Aires Ferreira

Condens. Matter 2018, 3(2), 18; https://doi.org/10.3390/condmat3020018 - 22 May 2018

Cited by 10 | Viewed by 5005

Abstract

We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin [...] Read more.

We present a unified theoretical framework for the study of spin dynamics and relativistic transport phenomena in disordered two-dimensional Dirac systems with pseudospin-spin coupling. The formalism is applied to the paradigmatic case of graphene with uniform Bychkov-Rashba interaction and shown to capture spin relaxation processes and associated charge-to-spin interconversion phenomena in response to generic external perturbations, including spin density fluctuations and electric fields. A controlled diagrammatic evaluation of the generalized spin susceptibility in the diffusive regime of weak spin-orbit interaction allows us to show that the spin and momentum lifetimes satisfy the standard Dyakonov-Perel relation for both weak (Gaussian) and resonant (unitary) nonmagnetic disorder. Finally, we demonstrate that the spin relaxation rate can be derived in the zero-frequency limit by exploiting the SU(2) covariant conservation laws for the spin observables. Our results set the stage for a fully quantum-mechanical description of spin relaxation in both pristine graphene samples with weak spin-orbit fields and in graphene heterostructures with enhanced spin-orbital effects currently attracting much attention. Full article

(This article belongs to the Special Issue Control and Enhancement of Quantum Coherence in Nanostructured Materials)

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7 pages, 1924 KiB

Open AccessArticle

Features of Metal Hydrogenation during Electron Irradiation

by Vitaliy Larionov, Yuriy Tyurin, Tatyana Murashkina and Thorsteinn Sigfusson

Condens. Matter 2018, 3(2), 17; https://doi.org/10.3390/condmat3020017 - 22 May 2018

Cited by 2 | Viewed by 2741

Abstract

This paper considers metal hydrogenation and hydrogen release from metals under electron irradiation. The study shows that there are two processes during irradiation: the increase in the hydrogen yield from metal and the increase in the ability of hydrogenated metal to accumulate the [...] Read more.

This paper considers metal hydrogenation and hydrogen release from metals under electron irradiation. The study shows that there are two processes during irradiation: the increase in the hydrogen yield from metal and the increase in the ability of hydrogenated metal to accumulate the energy of a beam of accelerated electrons. The energy introduced into hydrogenated metal is preserved for a longer period when compared to pure metal in time scales of electronic relaxation. Electron irradiation accelerates the saturation of metals with hydrogen and deuterium. Deuterium and hydrogen participate in the collective excitation of the internal hydrogen atmosphere of metals. This effect is explained by the nonequilibrium migration and release of hydrogen from metals. The migration of hydrogen isotopes during irradiation can be used to enhance the light isotope separation. Full article

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12 pages, 854 KiB

Open AccessArticle

The Study of Characteristic Environmental Sites Affected by Diverse Sources of Mineral Matter Using Compositional Data Analysis

by Antonio Speranza, Rosa Caggiano, Giulia Pavese and Vito Summa

Condens. Matter 2018, 3(2), 16; https://doi.org/10.3390/condmat3020016 - 7 May 2018

Cited by 8 | Viewed by 3341

Abstract

Compositional data analysis was applied on mineral element concentrations (i.e., Al, Ti, Si, Ca, Mg, Fe, Sr) content in PM₁₀, PM_2.5 and PM₁ simultaneous measurements at three characteristic environmental sites: kerbside, background and rural site. Different possible sources of [...] Read more.

Compositional data analysis was applied on mineral element concentrations (i.e., Al, Ti, Si, Ca, Mg, Fe, Sr) content in PM₁₀, PM_2.5 and PM₁ simultaneous measurements at three characteristic environmental sites: kerbside, background and rural site. Different possible sources of mineral trace elements affecting the PM in the considered sites were highlighted. Particularly, results show that compositional data analysis allows for the assessment of chemical/physical differences between mineral element concentrations of PM. These differences can be associated with both different kinds of involved mineral sources and different mechanisms of accumulation/dispersion of PM at the considered sites. Full article

(This article belongs to the Special Issue Condensed Matter Researches in Cryospheric Science)

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27 pages, 702 KiB

Open AccessArticle

Suppression of Quantum-Mechanical Collapse in Bosonic Gases with Intrinsic Repulsion: A Brief Review

by Boris A. Malomed

Condens. Matter 2018, 3(2), 15; https://doi.org/10.3390/condmat3020015 - 23 Apr 2018

Cited by 7 | Viewed by 3354

Abstract

It is known that attractive potential ~

- 1 / r^{2}

gives rise to the critical quantum collapse in the framework of the three-dimensional (3D) linear Schrödinger equation. This article summarizes theoretical analysis, chiefly published in several original papers, which demonstrates suppression [...] Read more.

It is known that attractive potential ~

- 1 / r^{2}

gives rise to the critical quantum collapse in the framework of the three-dimensional (3D) linear Schrödinger equation. This article summarizes theoretical analysis, chiefly published in several original papers, which demonstrates suppression of the collapse caused by this potential, and the creation of the otherwise missing ground state in a 3D gas of bosonic dipoles pulled by the same potential to the central charge, with repulsive contact interactions between them, represented by the cubic term in the respective Gross–Pitaevskii equation (GPE). In two dimensions (2D), quintic self-repulsion is necessary for the suppression of the collapse; alternatively, this may be provided by the effective quartic repulsion produced by the Lee–Huang–Yang correction to the GPE. 3D states carrying angular momentum are constructed in the model with the symmetry reduced from spherical to cylindrical by an external polarizing field. Interplay of the collapse suppression and miscibility–immiscibility transition is considered in a binary condensate. The consideration of the 3D setting in the form of the many-body quantum system, with the help of the Monte Carlo method, demonstrates that, although the quantum collapse cannot be fully suppressed, the self-trapped states predicted by the GPE exist in the many-body setting as metastable modes protected against the collapse by a tall potential barrier. Full article

(This article belongs to the Special Issue Proceedings of the conference SuperFluctuations 2017)

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15 pages, 332 KiB

Open AccessArticle

Effective Control of Chemical Potentials by Rabi Coupling with RF-Fields in Ultracold Mixtures

by Luca Lepori, Anna Maraga, Alessio Celi, Luca Dell’Anna and Andrea Trombettoni

Condens. Matter 2018, 3(2), 14; https://doi.org/10.3390/condmat3020014 - 17 Apr 2018

Cited by 4 | Viewed by 4651

Abstract

We show that a linear term coupling the atoms of an ultracold binary mixture provides a simple method to induce an effective and tunable population imbalance between them. This term is easily realized by Rabi coupling between different hyperfine levels of the same [...] Read more.

We show that a linear term coupling the atoms of an ultracold binary mixture provides a simple method to induce an effective and tunable population imbalance between them. This term is easily realized by Rabi coupling between different hyperfine levels of the same atomic species. The resulting effective imbalance holds for one-particle states dressed by the Rabi coupling and obtained by diagonalizing the mixing matrix of the Rabi term. This way of controlling the chemical potentials applies to both bosonic and fermionic atoms and it also allows for spatially- and temporally-dependent imbalances. As a first application, we show that, in the case of two attractive fermionic hyperfine levels with equal chemical potentials coupled by the Rabi pulse, the same superfluid properties of an imbalanced binary mixture are recovered. We finally discuss the properties of m-species mixtures in the presence of SU(m)-invariant interactions. Full article

(This article belongs to the Special Issue Proceedings of the conference SuperFluctuations 2017)

10 pages, 19904 KiB

Open AccessArticle

Formation and Oriented Aggregation of Tabular Hexagonal Silver Particles

by Lorenza Suber

Condens. Matter 2018, 3(2), 13; https://doi.org/10.3390/condmat3020013 - 14 Apr 2018

Cited by 5 | Viewed by 4092

Abstract

Silver tabular hexagonal particles (<diagonal> = 200 nm) were prepared at 40 °C by the reduction of silver nitrate with ascorbic acid in a solution of a polynaphthalene sulphonic dispersant agent, Daxad 19, in strong acidic conditions. By varying the reaction temperature and [...] Read more.

Silver tabular hexagonal particles (<diagonal> = 200 nm) were prepared at 40 °C by the reduction of silver nitrate with ascorbic acid in a solution of a polynaphthalene sulphonic dispersant agent, Daxad 19, in strong acidic conditions. By varying the reaction temperature and thus the dispersion viscosity between 10 °C and 30 °C, mesostructures of silver flat rods and flakes were obtained, the former resulting from linear aggregation of tabular hexagonal particles and the latter formed by intertwined flat rods. The results indicate an easy way to tune the aggregation of particles to obtain ordered mesostructures. 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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11 pages, 19695 KiB

Open AccessArticle

Decadal Climate Change in Ny-Ålesund, Svalbard, A Representative Area of the Arctic

by Minghu Ding, Shujie Wang and Weijun Sun

Condens. Matter 2018, 3(2), 12; https://doi.org/10.3390/condmat3020012 - 8 Apr 2018

Cited by 11 | Viewed by 6868

Abstract

In recent decades, global warming hiatus/slowdown has attracted considerable attention and has been strongly debated. Many studies suggested that the Arctic is undergoing rapid warming and significantly contributes to a continual global warming trend rather than a hiatus. In this study, we evaluated [...] Read more.

In recent decades, global warming hiatus/slowdown has attracted considerable attention and has been strongly debated. Many studies suggested that the Arctic is undergoing rapid warming and significantly contributes to a continual global warming trend rather than a hiatus. In this study, we evaluated the climate changes of Ny-Ålesund, Svalbard, a representative location of the northern North Atlantic sector of the Arctic, based on observational records from 1975–2014. The results showed that the annual warming rate was four times higher than the global mean (+0.76 °C·decade⁻¹) and was also much greater than Arctic average. Additionally, the warming trend of Ny-Ålesund started to slow down since 2005–2006, and our estimates showed that there is a 8–9 years-lagged, but significant, correlation between records of Ny-Ålesund and global HadCRUT4 datasets. This finding indicates that the Arctic was likely experiencing a hiatus pattern, which just appeared later than the low-mid latitudes due to transport processes of atmospheric circulations and ocean currents, heat storage effect of cryospheric components, multidecadal variability of Arctic cyclone activities, etc. This case study provides a new perspective on the global warming hiatus/slowdown debate. Full article

(This article belongs to the Special Issue Condensed Matter Researches in Cryospheric Science)

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18 pages, 2433 KiB

Open AccessArticle

Electronic Properties of Curved Few-Layers Graphene: A Geometrical Approach

by Marco Cariglia, Roberto Giambò and Andrea Perali

Condens. Matter 2018, 3(2), 11; https://doi.org/10.3390/condmat3020011 - 5 Apr 2018

Cited by 8 | Viewed by 6157

Abstract

We show the presence of non-relativistic Lévy-Leblond fermions in flat three- and four-layers graphene with AB stacking, extending the results obtained in Cariglia et al. 2017 for bilayer graphene. When the layer is curved we obtain a set of equations for Galilean fermions [...] Read more.

We show the presence of non-relativistic Lévy-Leblond fermions in flat three- and four-layers graphene with AB stacking, extending the results obtained in Cariglia et al. 2017 for bilayer graphene. When the layer is curved we obtain a set of equations for Galilean fermions that are a variation of those of Lévy-Leblond with a well defined combination of pseudospin, and that admit Lévy-Leblond spinors as solutions in an approriate limit. The local energy of such Galilean fermions is sensitive to the intrinsic curvature of the surface. We discuss the relationship between two-dimensional pseudospin, labelling layer degrees of freedom, and the different energy bands. For Lévy-Leblond fermions, an interpretation is given in terms of massless fermions in an effective 4D spacetime, and in this case the pseudospin is related to four dimensional chirality. A non-zero energy band gap between conduction and valence electronic bands is obtained for surfaces with positive curvature. Full article

(This article belongs to the Special Issue Control and Enhancement of Quantum Coherence in Nanostructured Materials)

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10 pages, 3566 KiB

Open AccessReview

Electromagnetic Field in Hybrid Quantum Plasmonic-Photonic Systems

by Bernardo Barbiellini, Subhabrata Das, Venkatesan Renugopalakrishnan and Ponniseril Somasundaran

Condens. Matter 2018, 3(2), 10; https://doi.org/10.3390/condmat3020010 - 2 Apr 2018

Cited by 5 | Viewed by 4391

Abstract

We study excitations and quantum optical properties of hybrid networks made up of metal nanoparticles, semiconductor quantum dots and molecules. Such processes can be used for the localization and the guiding of the electromagnetic field. Localized modes occurring in these networks and the [...] Read more.

We study excitations and quantum optical properties of hybrid networks made up of metal nanoparticles, semiconductor quantum dots and molecules. Such processes can be used for the localization and the guiding of the electromagnetic field. Localized modes occurring in these networks and the generation of confined fields are also connected to the enhancement of Raman-scattering occurring in these systems. We review some recent theoretical and computational studies of optical properties in hybrid nano-systems to gain control of light–matter interactions at the quantum level for efficient energy transport and sensing applications. Full article

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Condens. Matter, Volume 3, Issue 2 (June 2018) – 10 articles

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