Directed-Loop Equations for the 2D XY-Model with Ring Exchange in a Magnetic Field

2003 ◽  
Author(s):  
R. G. Melko
Keyword(s):  
Magnetic Field ◽  
Xy Model ◽  
Ring Exchange

Time evolution of quantum-memory-assisted entropic uncertainty relation and quantum correlations under dissipative environment

2019 ◽  
Vol 17 (01) ◽  
pp. 1950008 ◽  
Author(s):  
Mohammad Reza Pourkarimi
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Time Evolution ◽  
Uncertainty Relation ◽  
Quantum Correlations ◽  
Quantum Memory ◽  
Xy Model ◽  
Anisotropic Parameter ◽  
Entropic Uncertainty Relation ◽  
Dissipative Environment

By assuming the effect of dissipative environment and the Hamiltonian XY-model and external magnetic field, the time evolution of the entropic uncertainty relation (EUR) in the presence of quantum-memory and the dynamics of quantum correlations (QC) are investigated. It is shown that EUR and QC may evolve in different ways during the time. However, they can behave similarly when the time tends to infinity. The effects of external magnetic field and anisotropic parameter are different on the dynamics of EUR and QC.

The classical two-dimensional XY model with in-plane magnetic field

1990 ◽  
Vol 2 (7) ◽  
pp. 1853-1868 ◽  
Author(s):  
M E Gouvea ◽  
F G Mertens ◽  
A R Bishop ◽  
G M Wysin
Keyword(s):  
Magnetic Field ◽  
Xy Model ◽  
Two Dimensional

scholarly journals Spin wave theory of spin-1/2 XY model with ring exchange on a triangular lattice

2013 ◽  
Vol 91 (7) ◽  
pp. 542-547 ◽  
Author(s):  
Solomon A. Owerre
Keyword(s):  
Phase Transition ◽  
Spin Wave ◽  
Triangular Lattice ◽  
Finite Temperature ◽  
Wave Theory ◽  
Square Lattice ◽  
Xy Model ◽  
Superfluid Phase ◽  
Zero Temperature ◽  
Ring Exchange

We present the linear spin wave theory calculation of the superfluid phase of a hard-core boson J-K model with nearest neighbour exchange J and four-particle ring-exchange K at half filling on the triangular lattice, as well as the phase diagrams of the system at zero and finite temperatures. A similar analysis has been done on a square lattice (Schaffer et al. Phys. Rev. B, 80, 014503 (2009)). We find similar behaviour to that of a square lattice but with different spin wave values of the thermodynamic quantities. We also find that the pure J model (XY model), which has a well-known uniform superfluid phase with an ordered parameter [Formula: see text] at zero temperature is quickly destroyed by the inclusion of negative-K ring-exchange interactions, favouring a state with a (4π/3, 0) ordering wavevector. We further study the behaviour of the finite-temperature Kosterlitz–Thouless phase transition (TKT) in the uniform superfluid phase, by forcing the universal quantum jump condition on the finite-temperature spin wave superfluid density. We find that for K < 0, the phase boundary monotonically decreases to T = 0 at K/J = −4/3, where a phase transition is expected and TKT decreases rapidly, while for positive K, TKT reaches a maximum at some K ≠ 0. It has been shown on a square lattice using quantum Monte Carlo (QMC) simulations that for small K > 0 away from the XY point, the zero-temperature spin stiffness value of the XY model is decreased (Melko and Sandvik. Ann. Phys. 321, 1651 (2006)). Our result seems to agree with this trend found in QMC simulations for two-dimensional systems.

Numerical study of vortices in a two-dimensional XY model with in-plane magnetic field

1997 ◽  
Vol 55 (21) ◽  
pp. 14144-14147 ◽  
Author(s):  
M. E. Gouvêa ◽  
G. M. Wysin ◽  
A. S. T. Pires
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Xy Model ◽  
Two Dimensional

Article

1998 ◽  
Vol 76 (7) ◽  
pp. 507-513
Author(s):  
O Bolina ◽  
J R Parreira
Keyword(s):  
Magnetic Field ◽  
Transverse Magnetic Field ◽  
Ground State ◽  
Linear Chain ◽  
Critical Value ◽  
Transverse Magnetic ◽  
The State ◽  
Xy Model ◽  
The Magnetic Field

We show that the ground state of the xy model (ferromagnetic orantiferromagnetic) in a transverse magnetic field h --- for any spin value, in any dimension --- is the state with all spins aligned antiparallel to the field when h is greater than some critical value hc. In particular, for the spin-1/2 linear chain, we study the behavior of correlations as functions of the magnetic field. PACS Nos.: 75.10Jm and 64.60.Cm

ENTANGLEMENT IN THE XY HEISENBERG MODEL

2004 ◽  
Vol 18 (19n20) ◽  
pp. 1059-1065 ◽  
Author(s):  
XIN TIAN ◽  
JIA-TIH LIN ◽  
LIANG LIU ◽  
DE-LONG REN
Keyword(s):  
Magnetic Field ◽  
Critical Temperature ◽  
Ising Model ◽  
Heisenberg Model ◽  
Nonuniform Magnetic Field ◽  
Xy Model ◽  
Thermal Entanglement ◽  
Isotropic Model

We investigate the thermal entanglement of two-qubit anisotropic Heisenberg XY model in the presence of an external nonuniform magnetic field B along the z-axis. Concurrence, the measure of entanglement is calculated and its property is studied in different cases. Two best models, Ising model under a uniform magnetic and isotropic model in a nonuniform magnetic field, are discovered. In the two models, the critical temperature Tc (above which there is no entanglement) can be enhanced and its concurrence is maximal.

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