The Behavior of the Critical Magnetic Field and Correlation Functions in Finite-Size Hubbard-Like Models

1997 ◽  
Vol 11 (01n02) ◽  
pp. 147-152
Author(s):  
A.N. Kocharian
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Finite Size ◽  
Spin Correlation ◽  
Critical Magnetic Field ◽  
Spin Liquid ◽  
Lattice Geometry ◽  
Half Filling ◽  
Spin Flips ◽  
Spin Liquid State

We present exact analytical results for a critical field and correlations functions for N site ring and arbitrary size two dimensional coupled chains in a two component Hubbard model with a strong magnetic field and exactly at half-filling. The critical field near the Nagaoka instability with one spin and two spin flips is driven by Coulomb interaction, lattice geometry, dimensionality and crucially depends on the number of atomic sites N. Unsaturated ferromagnetism, reminiscent of Nagaoka-like behavior, and spin liquid state are examined in the structure of off-diagonal spin correlation at large U.

The Study on Surface Critical Magnetic Field of a Layered Magnetic Superconductors

2014 ◽  
Vol 979 ◽  
pp. 224-227 ◽  
Author(s):  
Sumitta Meakniti ◽  
Arpapong Changjan ◽  
Pongkaew Udomsamuthirun
Keyword(s):  
Magnetic Field ◽  
Magnetic Property ◽  
Variational Method ◽  
Critical Field ◽  
Landau Equation ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Ginzburg Landau Equation ◽  
Non Linear

In this research, we studied the surface critical magnetic field () of a layered magnetic superconductors by Ginzburg-Landau approach. After the 1st Ginzburg-Landau equation was calculated, a surface critical field was solved by variational method analytically. Our formula obtained was depended on the magnetic property of superconductor. We found that Hc3 of antiferromagnetism and paramagnetism superconductors were shown the same behaviour as non-magnetic superconductors. For diamagnetism and ferromagnetism superconductors, the higher and the lower values of critical magnetic field were found, respectively. However, the Hc3 was strongly depended on the non-linear of magnetic field intend of all kind magnetism.

scholarly journals MAGNETIC FIELD INDUCED GAP AND KINK BEHAVIOR OF THERMAL CONDUCTIVITY

2002 ◽  
Vol 16 (04) ◽  
pp. 107-116 ◽  
Author(s):  
E. J. FERRER ◽  
V. P. GUSYNIN ◽  
V. DE LA INCERA
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
External Magnetic Field ◽  
Critical Field ◽  
Applied Magnetic Field ◽  
Interaction Model ◽  
Critical Magnetic Field ◽  
Landau Levels

The thermal conductivity of a quasiparticle (QP) system described by a relativistic four-fermion interaction model in the presence of an external magnetic field is calculated. It is shown that, for narrow widths of quasiparticles, the thermal conductivity, as a function of the applied magnetic field, exhibits a kink behavior at a critical field B c ~ T2. The kink is due to the opening of a gap in the QP spectrum at a critical magnetic field B c and to the enhancement of the transitions between the zeroth and first Landau levels. Possible applications of the results are discussed.

Anwendung der Methode der Korrelationsfunktion auf die Berechnung der Richtungsabhängigkeit von Hc2 im kubischen Einkristall

1970 ◽  
Vol 25 (8-9) ◽  
pp. 1161-1168 ◽  
Author(s):  
Klaus-Dieter Harms
Keyword(s):  
Magnetic Field ◽  
Correlation Function ◽  
Critical Field ◽  
Upper Critical Field ◽  
Critical Magnetic Field ◽  
Higher Order ◽  
Eigenvalue Equation ◽  
Cubic Symmetry ◽  
Upper Critical Magnetic Field

Abstract The upper critical magnetic field for a monocrystalline superconductor with cubic symmetry is calculated using the Method of the Correlation Function. The symmetry of the system leads to an eigenvalue equation which is solved with perturbation-theoretic methods. The upper critical field is calculated for dirty superconductors in the lowest order for which anisotropy is present. For clean superconductors, a higher order is calculated. Some results are critically compared with those in a paper by HOHENBERG and WERTHAMER.

scholarly journals Topological thermal Hall effect for topological excitations in spin liquid: Emergent Lorentz force on the spinons

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Yong Hao Gao ◽  
Gang Chen
Keyword(s):  
Hall Effect ◽  
Lorentz Force ◽  
Spin Correlation ◽  
Spin Liquid ◽  
Spin Liquids ◽  
Topological Excitations ◽  
Lattice Geometry ◽  
Field Correlation ◽  
Moriya Interaction ◽  
Scattering Measurement

We study the origin of Lorentz force on the spinons in a U(1) spin liquid. We are partly inspired by the previous observation of gauge field correlation in the pairwise spin correlation using the neutron scattering measurement by P.A. Lee an N. Nagaosa [PhysRevB 87,064423(2013)] when the Dzyaloshinskii-Moriya interaction intertwines with the lattice geometry. We extend this observation to the Lorentz force that exerts on the (neutral) spinons. The external magnetic field, that polarizes the spins, effectively generates an internal U(1) gauge flux for the spinons and twists the spinon motion through the Dzyaloshinskii-Moriya interaction. Such a mechanism for the emergent Lorentz force differs fundamentally from the induction of the internal U(1) gauge flux in the weak Mott insulating regime from the charge fluctuations. We apply this understanding to the specific case of spinon metals on the kagome lattice. Our suggestion of emergent Lorentz force generation and the resulting topological thermal Hall effect may apply broadly to other non-centrosymmetric spin liquids with Dzyaloshinskii-Moriya interaction. We discuss the relevance with the thermal Hall transport in kagome materials volborthite and kapellasite.

LOCAL MINIMIZERS FOR THE GINZBURG–LANDAU ENERGY NEAR CRITICAL MAGNETIC FIELD: PART II

1999 ◽  
Vol 01 (03) ◽  
pp. 295-333 ◽  
Author(s):  
SYLVIA SERFATY
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Critical Magnetic Field ◽  
Asymptotic Limit ◽  
Local Minimizers ◽  
Ginzburg Landau ◽  
London Equation ◽  
Stable Solutions

As in Part I, we study local minimizers of the Ginzburg–Landau energy (depending on κ → +∞) for superconductors in a prescribed magnetic field hex. For disc domains, we find and describe stable solutions of the associated equations and show how vortices appear as hex is raised from the first critical field Hc1. We also study the asymptotic limit κ→∞ for hex=Hc1 and prove that the limiting magnetic field in the superconductor satisfies the London equation.

Functional derivatives for the critical magnetic field of Pb

1978 ◽  
Vol 56 (9) ◽  
pp. 1248-1254 ◽  
Author(s):  
J. M. Daams ◽  
J. P. Carbotte
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
Critical Field ◽  
Coulomb Repulsion ◽  
Critical Magnetic Field ◽  
Deviation Function ◽  
Functional Derivatives ◽  
First Time ◽  
Reduced Temperature ◽  
Good Agreement

We have calculated for superconducting Pb in the dirty (isotropic) limit the following functional derivatives: δTc/δα2F(ω), δHc(0)/δα2F(ω), δD(t)/δα2F(ω), ∂Tc/∂μ*, ∂Hc(0)/∂μ*, and ∂D(t)/∂μ*, where Tc, Hc(0), D(t), t, α2(ω)F(ω), and μ* are, respectively, the critical temperature, critical field at T = 0, deviation function for the critical field, reduced temperature T/Tc, electron–phonon spectral density, and Coulomb repulsion parameter. Our values for the first two functional derivatives are in good agreement with previous work by Rainer and Bergmann. We present the others here for the first time to relate the observed changes in Tc, Hc(0), and D(t) under hydrostatic pressure to the change in α2(ω)F(ω) and μ*.

FINITE-SIZE CALCULATION OF ANISOTROPIC ANTIFERROMAGNETIC CHAINS AT NONZERO FIELD

1996 ◽  
Vol 10 (12) ◽  
pp. 1453-1468
Author(s):  
G.G. CABRERA ◽  
S. WEINKETZ ◽  
DJALMA MEDEIROS
Keyword(s):  
Magnetic Field ◽  
Analytical Solutions ◽  
Size Effects ◽  
Heisenberg Model ◽  
Finite Size ◽  
Accurate Method ◽  
Critical Magnetic Field ◽  
Exact Analytical Solutions ◽  
Finite Systems ◽  
Antiferromagnetic Spin

The antiferromagnetic spin-1/2 Heisenberg model, with axial anisotropy and applied magnetic field parallel to the axis, is solved numerically by Lanczos diagonalization of finite systems. We devise an extremely accurate method that allows for a reliable extrapolation to the infinite size limit. In the above limit, our results are compared with exact analytical solutions obtained through the Bethe ansatz. As an important example, we probe the behavior of the Critical Magnetic Field in the whole anisotropic region. We find indications that suggest the presence of two different regimes for the scaling of size effects as a function of the anisotropy.

MAGNETIC EFFECTS AND CURRENT SENSITIVITY OF SUPERCONDUCTING FILMS

1936 ◽  
Vol 14a (2) ◽  
pp. 25-37 ◽  
Author(s):  
A. D. Misener
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Threshold Current ◽  
Superconducting Films ◽  
Anomalous Behavior ◽  
Critical Magnetic Field ◽  
Threshold Field ◽  
Current Sensitivity ◽  
Transition Points ◽  
Different Diameters

The work described in this paper is a continuation of the investigation of the anomalous behavior of superconducting metals in the form of thin films (12.2–0.3 μ). The manner in which an external magnetic field will penetrate when applied to superconducting films of various thicknesses at a variety of temperatures below their transition points has been studied. It is found that there is a critical field that will penetrate the film, and that this field is less than the threshold field required to restore the resistance of the film at the same temperature. Even for fields much larger than the threshold field, the films act as partial magnetic shields and diminish the field strength by an almost constant amount.By measuring the current required to restore the resistance of films formed on cylindrical supports of different diameters, it is shown that their current sensitivity is due to a surface density of current. The critical magnetic field associated with this threshold current is less than either the threshold field (external) or the critical field for penetration. The similarity between these effects and those found for certain superconducting alloys is discussed.

Magnetic field necessary to destroy superconductivity in Al-type Se and Te

1978 ◽  
Vol 56 (9) ◽  
pp. 1133-1135 ◽  
Author(s):  
Carlo Reale
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Annealing Temperature ◽  
Bulk Material ◽  
Critical Magnetic Field ◽  
Normal Phase ◽  
Zero Field ◽  
Superconducting Transition ◽  
Cyclic Annealing ◽  
Glass Substrates

This paper reports the results of a study of the critical magnetic field required to restore electrical resistance in superconducting metastable Al-type Se and Te overlays vapor-quenched, respectively, on MgO, FeO, CoO, or NiO and CaO or MnO base films quench-condensed on glass substrates. The critical field was measured at various temperatures, from the superconducting transition temperature in zero field down to 0.1 K, for overlay thicknesses ranging from 100 Å up to values at which size effects disappear. The measurements were repeated after cyclic annealing at increasing temperatures up to a limiting temperature at which the overlay breaks owing to the transformation of the A1-type modification to the less dense ordinary A8-type structure.The critical field decreases steeply, with increasing thickness, down to a constant bulk-material value, increases nearly parabolically, with decreasing temperature, up to an extrapolable absolute-zero value, and decreases irreversibly with increasing annealing temperature. The superconducting-to-normal phase transition occurs through an intermediate state, which indicates that quench-deposited A1-type Se and Te are soft superconductors.

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