Thermal entanglement and sharp specific-heat peak in an exactly solved spin-1/2 Ising-Heisenberg ladder with alternating Ising and Heisenberg inter-leg couplings

Abstract

The spin-1/2 Ising-Heisenberg two-leg ladder accounting for alternating Ising and Heisenberg inter-leg couplings in addition to the Ising intra-leg coupling is rigorously mapped onto to a mixed spin-(3/2,1/2) Ising-Heisenberg diamond chain with the nodal Ising spins $S=3/2$ and the interstitial spin-1/2 Heisenberg dimers. The latter effective model with higher-order interactions between the nodal and interstitial spins is subsequently exactly solved within the transfer-matrix method. The model under investigation exhibits five different ground states: ferromagnetic, antiferromagnetic, superantiferromagnetic and two types of frustrated ground states with a non-zero residual entropy. A detailed study of thermodynamic properties reveals an anomalous specific-heat peak at low enough temperatures, which is strongly reminiscent because of its extraordinary height and sharpness to an anomaly accompanying a phase transition. It is convincingly evidenced, however, that the anomalous peak in the specific heat is finite and it comes from vigorous thermal excitations from a two-fold degenerate ground state towards a macroscopically degenerate excited state. Thermal entanglement between the nearest-neighbor Heisenberg spins is also comprehensively explored by taking advantage of the concurrence. The threshold temperature delimiting a boundary between the entangled and disentangled parameter space may show presence of a peculiar temperature reentrance.

9 pages, 9 figures

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• Low temperature pseudo-phase transition in an extended Hubbard diamond chain
• Local distributions of the 1D dilute Ising model
• Pseudo-transition between antiferromagnetic and charge orders in a minimal spin-pseudospin model of one-dimensional cuprates
• Residual entropy of the dilute Ising chain in a magnetic field
• Thermodynamic features of the 1D dilute Ising model in the external magnetic field
• Pseudotransitions in a dilute Ising chain
• Zero temperature phase transitions and their anomalous influence on thermodynamic behavior in the q-state Potts model on a diamond chain
• Finite size effects around pseudo-transition in one-dimensional models with nearest neighbor interaction
• Quantum Otto engine mimicking Carnot near pseudotransitions in the one-dimensional extended Hubbard model in the atomic limit
• Dual thermal pseudocritical features in a spin-1/2 Ising chain with twin-diamond geometry
• Spectral mechanism and nearly reducible transfer matrices for pseudotransitions in one-dimensional systems