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We discuss the correlations between particles of different momentum in a superfluid Fermi gas, accessible through noise measurements of the absorption images of the expanded gas. We include two elements missing from the simplest t...
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We discuss the correlations between particles of different momentum in a superfluid Fermi gas, accessible through noise measurements of the absorption images of the expanded gas. We include two elements missing from the simplest treatment, based on the BCS wavefunction: the explicit use of a conserving approximation satisfying particle number conservation and the inclusion of the contribution from Cooper pairs at finite momentum. We expect the latter to be a significant issue in the strongly correlated state emerging in the BCS-Bose-Einstein condensate (BEC) crossover.
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Calculations of the field profiles and current distributions at the remanence state of NxN square-columnar Josephson-junction arrays with two vortices show that, although it is possible for each vortex to contain a flux appreciabl...
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Calculations of the field profiles and current distributions at the remanence state of NxN square-columnar Josephson-junction arrays with two vortices show that, although it is possible for each vortex to contain a flux appreciably less than Phi(0)/2 when N=25, it is still an incomplete vortex of the conventional Phi(0) type since this flux approaches Phi(0) continuously as N-->infinity. This phenomenon is explained by the unique feature of gauge invariant phase differences and the Josephson energy in such arrays. [References: 10]
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We study vortex unbinding for the classical two-dimensional XY model in a magnetic field on square and triangular lattices. A renormalization group analysis combined with duality in the model shows that at high temperature and hig...
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We study vortex unbinding for the classical two-dimensional XY model in a magnetic field on square and triangular lattices. A renormalization group analysis combined with duality in the model shows that at high temperature and high field, the vortices unbind as the magnetic field is lowered in a two-step process: strings of overturned spins first proliferate and then vortices unbind. The transitions are highly continuous but are not of the Kosterlitz-Thouless type. The unbound vortex fixed point is shown to inherit properties of the underlying lattice, in particular containing a set of nodal lines that reflect the lattice symmetry. (C) 2003 Elsevier Science (USA). All rights reserved. [References: 23]
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Mott insulators with strong spin-orbit coupling display a strongly anisotropic response to applied magnetic fields. This applies in particular to Kitaev materials, with alpha-RuCl3 and Na2IrO3 representing two important examples. ...
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Mott insulators with strong spin-orbit coupling display a strongly anisotropic response to applied magnetic fields. This applies in particular to Kitaev materials, with alpha-RuCl3 and Na2IrO3 representing two important examples. Both show a magnetically ordered zigzag state at low temperatures, and considerable effort has been devoted to properly modeling these systems in order to identify routes towards realizing a quantum spin liquid. Here, we investigate the relevant Heisenberg-Kitaev-Gamma model primarily at elevated temperatures, focusing on the characteristic anisotropy between the in-plane and out-of-plane uniform susceptibility. For alpha-RuCl3, we find that the experimentally observed anisotropy, including its temperature dependence, can be reproduced by combining a large off-diagonal Gamma(1) coupling with a moderate g-factor anisotropy. Moreover, we study in detail the effect of magnetic dilution and provide predictions for the doping evolution of the temperature-dependent susceptibilities.
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We report the structural, magnetic, specific heat, and electronic structure studies of the material K3Yb(VO4)(2), which has two-dimensional triangular layers constituted by rare-earth magnetic Yb3+ ions. Magnetic susceptibility da...
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We report the structural, magnetic, specific heat, and electronic structure studies of the material K3Yb(VO4)(2), which has two-dimensional triangular layers constituted by rare-earth magnetic Yb3+ ions. Magnetic susceptibility data show the absence of magnetic long-range order down to 0.5K. No bifurcation is observed between zero-field-cooled and field-cooled magnetic susceptibility data, ruling out the possibility of spin-glassiness down to 0.5K. From the fit to magnetic susceptibility data with Curie-Weiss law in the low-temperature region, the observed Curie-Weiss temperature (theta(CW)) is about -1K, implying an antiferromagnetic coupling between the Yb3+ ions. Magnetic field-dependent specific heat fits well with two-level Schottky behavior. The analysis of magnetization and specific heat data confirms that the Yb3+ ion hosts the effective spin J(eff) = 1/2 state. To provide a microscopic understanding of the ground state nature of the titled material, we carried out state-of-the-art first-principles calculations based on density functional theory + Hubbard U and density functional theory + dynamical mean-field theory approaches. Our calculations reveal that the system belongs to the novel class of spin-orbit driven Mott Hubbard insulators and possesses large in-plane magnetocrystalline anisotropy.
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Aspects of isomorph theory, Rosenfeld-Tarazona temperature scaling, and thermodynamic geometry are comparatively discussed on the basis of the Lennard-Jones potential. The first two approaches approximate the high-density fluid st...
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Aspects of isomorph theory, Rosenfeld-Tarazona temperature scaling, and thermodynamic geometry are comparatively discussed on the basis of the Lennard-Jones potential. The first two approaches approximate the high-density fluid state well when the repulsive interparticle interactions become dominant, which is typically the case close to the freezing line. However, previous studies of Rosenfeld-Tarazona scaling for the isochoric heat capacity and its relation to isomorph theory reveal deviations for the temperature dependence. It turns out that a definition of a state region in which repulsive interactions dominate is required for achieving consistent results. The Riemannian thermodynamic scalar curvature R allows for such a classification, indicating predominantly repulsive interactions by R > 0. An analysis of the isomorphic character of the freezing line and the validity of Rosenfeld-Tarazona temperature scaling show that these approaches are consistent only in a small state region.
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Model of s-wave and d-wave superconductivity in a singular Fermi liquid with a divergent scattering amplitude for particles with the same quasi-momenta and opposite spins is formulated and presented with regard to a narrow, nearly...
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Model of s-wave and d-wave superconductivity in a singular Fermi liquid with a divergent scattering amplitude for particles with the same quasi-momenta and opposite spins is formulated and presented with regard to a narrow, nearly half-filled conduction band. The ground state and other eigenstates for the superconducting phase are found. Thermodynamic functions are obtained by the use of the Bogolubov method. The gap equation along with the equation for the chemical potential is derived in a general form and solved in a self-consistent manner for s-wave pairing. Above a certain temperature there are two solutions of the gap equation, however only for the greater one the superconducting phase remains stable. It is shown that the system undergoes a first-order phase transition between the superconducting and the normal phase. The critical temperature and the heat of the transition are found. The temperature dependence of the entropy and the specific heat of the system is also presented. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. [References: 10]
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We report a thorough characterization of the glassy phases of mixtures of succinonitrile and glutaronitrile via dielectric spectroscopy and differential scanning calorimetry. This system is revealed to be one of the rare examples ...
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We report a thorough characterization of the glassy phases of mixtures of succinonitrile and glutaronitrile via dielectric spectroscopy and differential scanning calorimetry. This system is revealed to be one of the rare examples where both glassy states of matter, a structurally disordered supercooled liquid and an orientationally disordered plastic crystal, can be prepared in the same material. Both disordered states can be easily supercooled, finally arriving at a structural-glass or a glassycrystal state. Detailed investigations using broadband dielectric spectroscopy enable a comparison of the glassy dynamics in both phases. Just as previously demonstrated for supercooled-liquid and plastic-crystalline ethanol, our experiments reveal very similar relaxational behavior and glass temperatures of both disordered states. Thus the prominent role of orientational degrees of freedom in the glass transition, suggested on the basis of the findings for ethanol, is fully corroborated by the present work.Moreover, the fragilities of both phases are determined and compared for different mixtures. The findings can be qualitatively understood within an energy-landscape based explanation of fragility.
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The phase behavior of polyamorphous systems based on modified Van der Waals equation with several critical points is investigated in the article. A model of phase equilibria in binary polyamorphous systems, including liquid-liquid...
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The phase behavior of polyamorphous systems based on modified Van der Waals equation with several critical points is investigated in the article. A model of phase equilibria in binary polyamorphous systems, including liquid-liquid equilibria in one-component systems and evaluation of critical lines in a binary mixture.It is proposed an algorithm for the search of parameters according to the excluded volume for Van der Waals model from density and temperature, which makes it possible to generate more than one critical point in a one-component fluid. To test the hypothesis of the continuity of critical lines in binary mixtures of polyamorphous fluids as an initial approximation used parameters near the critical point of the second component. Calculation of critical curves for binary polyamorphous mixtures confirmed the continuity of the transition from a stable critical point of the first metastable point of the second.
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Two new isostructural antiferromagnets Ba2M3(C2O4)(3)(OH) 4 center dot 3H(2)O (M = Ni, Co) are synthesized by the traditional hydrothermal method. The basic magnetic unit of this system is a spin hexamer constituted by two non-cop...
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Two new isostructural antiferromagnets Ba2M3(C2O4)(3)(OH) 4 center dot 3H(2)O (M = Ni, Co) are synthesized by the traditional hydrothermal method. The basic magnetic unit of this system is a spin hexamer constituted by two non-coplanar triangular rings. The magnetic spin hexamers were connected with each other by oxalate groups, forming a two-dimensional framework along the ab plane. Susceptibility, magnetization, and specific heat have been measured to study the magnetism of this system. Ba2Ni3(C2O4)(3)(OH) 4 center dot 3H(2)O (Ni compound) exhibits two magnetic transitions at T-1 = 20 K and T-2 = 12 K with Weiss temperature theta(W) = -135.65 K. However, Ba2Co3(C2O4)(3)(OH)(4)center dot 3H(2)O (Co compound) undergoes one magnetic transition at T-1 = 10 K with Weiss temperature theta(W) = -85.03 K. It is found that both compounds are frustrated antiferromagnets with the frustrated factor of f = 6.8 for the Ni compound and f = 8.5 for the Co compound. The possible origin of spin frustration is discussed.
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