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Equilibrium and dynamical properties of the ANNNI chain at the multiphase point

Abhishek Dhar·B. Sriram Shastry·Chandan Dasgupta
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Abstract

We study the equilibrium and dynamical properties of the ANNNI (axial next-nearest-neighbor Ising) chain at the multiphase point. An interesting property of the system is the macroscopic degeneracy of the ground state leading to finite zero-temperature entropy. In our equilibrium study we consider the effect of softening the spins. We show that the degeneracy of the ground state is lifted and there is a qualitative change in the low temperature behaviour of the system with a well defined low temperature peak of the specific heat that carries the thermodynamic ``weight'' of the ground state entropy. In our study of the dynamical properties, the stochastic Kawasaki dynamics is considered. The Fokker-Planck operator for the process corresponds to a quantum spin Hamiltonian similar to the Heisenberg ferromagnet but with constraints on allowed states. This leads to a number of differences in its properties which are obtained through exact numerical diagonalization, simulations and by obtaining various analytic bounds.

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Abhishek Dhar, B. Sriram Shastry, Chandan Dasgupta. 2000-04-13. Equilibrium and dynamical properties of the ANNNI chain at the multiphase point. https://doi.org/10.1103/physreve.62.1592

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