Search results for "XY model"
showing 4 items of 14 documents
Thermodynamics of the two-dimensional Heisenberg classical honeycomb lattice
1998
In this article we adapt a previous work concerning the two-dimensional (2D) Heisenberg classical square lattice [Physica B 245, 263 (1998)] to the case of a honeycomb lattice. Closed-form expressions of the main thermodynamic functions of interest are derived in the zero-field limit. Notably, near absolute zero (i.e., the critical temperature), we derive the values of the critical exponents $\ensuremath{\alpha}=0,\ensuremath{\eta}=\ensuremath{-}1,\ensuremath{\gamma}=3,$ and $\ensuremath{\nu}=1,$ as for the square lattice, thus proving their universal character. A very simple model allows one to give a good description of the low-temperature behaviors of the product $\ensuremath{\chi}T.$ Fo…
Geometric phases and criticality in spin chain systems
2005
A relation between geometric phases and criticality of spin chains is established. As a result, we show how geometric phases can be exploited as a tool to detect regions of criticality without having to undergo a quantum phase transition. We analytically evaluate the geometric phase that correspond to the ground and excited states of the anisotropic XY model in the presence of a transverse magnetic field when the direction of the anisotropy is adiabatically rotated. Ultra-cold atoms in optical lattices are presented as a possible physical realization.
Quantum Hopfield Model
2020
We find the free-energy in the thermodynamic limit of a one-dimensional XY model associated to a system of N qubits. The coupling among the &sigma
Monte Carlo study of asymmetric 2D XY model
1997
Employing the Polyakov-Susskind approximation in a field theoretical treatment, the t-J model for strongly correlated electrons in two dimensions has recently been shown to map effectively onto an asymmetric two-dimensional classical XY model. The critical temperature at which charge-spin separation occurs in the t-J model is determined by the location of the phase transitions of this effective model. Here we report results of Monte Carlo simulations which map out the complete phase diagram in the two-dimensional parameter space and also shed some light on the critical behaviour of the transitions.