Condensed Matter

12 pages, 357 KiB

Open AccessArticle

Fermionic Properties of Two Interacting Bosons in a Two-Dimensional Harmonic Trap

by Pere Mujal, Artur Polls and Bruno Juliá-Díaz

Condens. Matter 2018, 3(1), 9; https://doi.org/10.3390/condmat3010009 - 15 Mar 2018

Cited by 7 | Viewed by 3942

The system of two interacting bosons in a two-dimensional harmonic trap is compared with the system consisting of two noninteracting fermions in the same potential. In particular, we discuss how the properties of the ground state of the system, e.g., the different contributions [...] Read more.

The system of two interacting bosons in a two-dimensional harmonic trap is compared with the system consisting of two noninteracting fermions in the same potential. In particular, we discuss how the properties of the ground state of the system, e.g., the different contributions to the total energy, change as we vary both the strength and range of the atom–atom interaction. In particular, we focus on the short-range and strong interacting limit of the two-boson system and compare it to the noninteracting two-fermion system by properly symmetrizing the corresponding degenerate ground state wave functions. In that limit, we show that the density profile of the two-boson system has a tendency similar to the system of two noninteracting fermions. Similarly, the correlations induced when the interaction strength is increased result in a similar pair correlation function for both systems. Full article

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

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10 pages, 6682 KiB

Open AccessArticle

The BKT Universality Class in the Presence of Correlated Disorder

by Ilaria Maccari, Lara Benfatto and Claudio Castellani

Condens. Matter 2018, 3(1), 8; https://doi.org/10.3390/condmat3010008 - 09 Mar 2018

Cited by 13 | Viewed by 4052

Abstract

The correct detection of the Berezinskii-Kosterlitz-Thouless (BKT) transition in quasi-two-dimensional superconductors still remains a controversial issue. Its main signatures, indeed, are often at odds with the theoretical expectations. In a recent work (Maccari, I.; Benfatto, L.; Castellani, C. Phys. Rev. B 2017, 96, [...] Read more.

The correct detection of the Berezinskii-Kosterlitz-Thouless (BKT) transition in quasi-two-dimensional superconductors still remains a controversial issue. Its main signatures, indeed, are often at odds with the theoretical expectations. In a recent work (Maccari, I.; Benfatto, L.; Castellani, C. Phys. Rev. B 2017, 96, 060508), we have shown that the presence of spatially correlated disorder plays a key role in this sense because it is the reason underlying the experimentally-observed smearing of the universal superfluid-density jump. In the present paper we closely investigate the effects of correlated disorder on the BKT transition, specifically addressing the issue of whether or not it changes the BKT universality class. Full article

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

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10 pages, 1846 KiB

Open AccessArticle

Ground-State Magnetization in Mixtures of a Few Ultra-Cold Fermions in One-Dimensional Traps

by Tomasz Sowiński

Condens. Matter 2018, 3(1), 7; https://doi.org/10.3390/condmat3010007 - 06 Mar 2018

Cited by 4 | Viewed by 3134

Abstract

Ground-state properties of a few spin-

1 / 2

ultra-cold fermions confined in a one-dimensional trap are studied by the exact diagonalization method. In contrast to previous studies, it is not assumed that the projection of a spin of individual particles is fixed. [...] Read more.

Ground-state properties of a few spin-

1 / 2

ultra-cold fermions confined in a one-dimensional trap are studied by the exact diagonalization method. In contrast to previous studies, it is not assumed that the projection of a spin of individual particles is fixed. Therefore, the spin is treated as an additional degree of freedom and the global magnetization of the system is established spontaneously. Depending on the shape of the trap, inter-particle interactions, and an external magnetic field, the phase diagram of the system is determined. It is shown that, for particular confinements, some values of the magnetization cannot be reached by the ground-state of the system. Full article

(This article belongs to the Special Issue New Trends in Quantum Complex Matter)

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9 pages, 1521 KiB

Open AccessArticle

VUV Pump and Probe of Phase Separation and Oxygen Interstitials in La₂NiO_4+y Using Spectromicroscopy

by Antonio Bianconi, Augusto Marcelli, Markus Bendele, Davide Innocenti, Alexei Barinov, Nathalie Poirot and Gaetano Campi

Condens. Matter 2018, 3(1), 6; https://doi.org/10.3390/condmat3010006 - 11 Feb 2018

Cited by 2 | Viewed by 3851

Abstract

While it is known that strongly correlated transition metal oxides described by a multi-band Hubbard model show microscopic multiscale phase separation, little is known about the possibility to manipulate them with vacuum ultraviolet (VUV), 27 eV lighting. We have investigated the photo-induced effects [...] Read more.

While it is known that strongly correlated transition metal oxides described by a multi-band Hubbard model show microscopic multiscale phase separation, little is known about the possibility to manipulate them with vacuum ultraviolet (VUV), 27 eV lighting. We have investigated the photo-induced effects of VUV light illumination of a super-oxygenated La₂NiO_4+y single crystal by means of scanning photoelectron microscopy. VUV light exposure induces the increase of the density of states (DOS) in the binding energy range around E_b = 1.4 eV below E_F. The photo-induced states in this energy region have been predicted due to clustering of oxygen interstitials by band structure calculations for large supercell of La₂CuO_4.125. We finally show that it is possible to generate and manipulate oxygen rich domains by VUV illumination as it was reported for X-ray illumination of La₂CuO_4+y. This phenomenology is assigned to oxygen-interstitials ordering and clustering by photo-illumination forming segregated domains in the La₂NiO_4+y surface. Full article

(This article belongs to the Special Issue New Trends in Quantum Complex Matter)

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14 pages, 280 KiB

Open AccessArticle

Effects of Symmetry Breaking in Resonance Phenomena

by Vyacheslav I. Yukalov and Elizaveta P. Yukalova

Condens. Matter 2018, 3(1), 5; https://doi.org/10.3390/condmat3010005 - 01 Feb 2018

Cited by 1 | Viewed by 3018

Abstract

We show that resonance phenomena can be treated as nonequilibrium phase transitions. Resonance phenomena, similar to equilibrium phase transitions, are accompanied by some kind of symmetry breaking and can be characterized by order parameters. This is demonstrated for spin-wave resonance, helicon resonance, and [...] Read more.

We show that resonance phenomena can be treated as nonequilibrium phase transitions. Resonance phenomena, similar to equilibrium phase transitions, are accompanied by some kind of symmetry breaking and can be characterized by order parameters. This is demonstrated for spin-wave resonance, helicon resonance, and spin-reversal resonance. Full article

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3 pages, 162 KiB

Open AccessEditorial

Layered Superconductors

by Yoshikazu Mizuguchi

Condens. Matter 2018, 3(1), 4; https://doi.org/10.3390/condmat3010004 - 01 Feb 2018

Viewed by 2727

Abstract

Since the discovery of cuprates (Cu-oxide superconductors) in 1986 [1–4], layered superconductors have attracted much attention, due to the emergence of high-transition-temperature (high-T_c) and unconventional superconductivity. Full article

(This article belongs to the Special Issue Layered Superconductors)

2 pages, 139 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Condensed Matter in 2017

by Condensed Matter Editorial Office

Condens. Matter 2018, 3(1), 3; https://doi.org/10.3390/condmat3010003 - 12 Jan 2018

Viewed by 2175

Abstract

Peer review is an essential part in the publication process, ensuring that Condensed Matter maintains high quality standards for its published papers[...] Full article

11 pages, 444 KiB

Open AccessArticle

Two-Time Correlation Functions in Dissipative and Interacting Bose–Hubbard Chains

by Zakari Denis and Sandro Wimberger

Condens. Matter 2018, 3(1), 2; https://doi.org/10.3390/condmat3010002 - 03 Jan 2018

Cited by 5 | Viewed by 4104

Abstract

A method is presented for the systematic derivation of a hierarchy of coupled equations for the computation of two-time correlation functions of operators for open many-body quantum systems. We show how these systems of equations can be closed in mean-field and beyond approximations. [...] Read more.

A method is presented for the systematic derivation of a hierarchy of coupled equations for the computation of two-time correlation functions of operators for open many-body quantum systems. We show how these systems of equations can be closed in mean-field and beyond approximations. Results for the specific example of the spectral weight functions are discussed. Our method allows one to access the full temporal evolution, not just the stationary solution, of non-equilibrium open quantum problems described by a Markovian master equation. Full article

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

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3655 KiB

Open AccessArticle

Single Crystal Growth and Superconducting Properties of Antimony-Substituted NdO_0.7F_0.3BiS₂

by Satoshi Demura, Satoshi Otsuki, Yuita Fujisawa, Yoshihiko Takano and Hideaki Sakata

Condens. Matter 2018, 3(1), 1; https://doi.org/10.3390/condmat3010001 - 27 Dec 2017

Cited by 2 | Viewed by 3286

Abstract

Antimony (Sb) substitution of less than 8% was examined on a single crystal of a layered superconductor NdO_0.7F_0.3BiS₂. The superconducting transition temperature of the substituted samples decreased as Sb concentration increased. A lattice constant along the c [...] Read more.

Antimony (Sb) substitution of less than 8% was examined on a single crystal of a layered superconductor NdO_0.7F_0.3BiS₂. The superconducting transition temperature of the substituted samples decreased as Sb concentration increased. A lattice constant along the c-axis showed a large decrease compared with that along the a-axis. Since in-plane chemical pressure monotonically decreased as Sb concentration increased, the suppression of the superconductivity is attributed to the decrease in the in-plane chemical pressure. Full article

(This article belongs to the Special Issue Layered Superconductors)

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Condens. Matter, Volume 3, Issue 1 (March 2018) – 9 articles

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