Low-temperature thermodynamics of spin-1/2 orthogonal-dimer chain with Ising and Heisenberg interactions

TL;DR

This paper analyzes the low-temperature thermodynamics of an exactly solvable quantum spin-1/2 orthogonal-dimer chain with mixed Ising and Heisenberg interactions, revealing fractional magnetization plateaux and ground state degeneracies.

Contribution

It introduces an exactly solvable model combining Heisenberg and Ising interactions and explores its low-temperature thermodynamic behavior near critical fields.

Findings

Fractional magnetization plateaux at 1/4 and 1/2 of saturation.

Highly degenerate ground states at critical fields.

Low-temperature specific heat behavior explained by lattice-gas model.

Abstract

We consider an exactly solvable version of the quantum spin-1/2 orthogonal-dimer chain with the Heisenberg intra-dimer and Ising inter-dimer couplings. The investigated quantum spin system exhibits at zero temperature fractional plateaux at 1/4 and 1/2 of the saturation magnetization and it has a highly degenerate ground state at critical fields where the magnetization jumps. We study the field dependence of the specific heat at low temperature. The lattice-gas description is formulated in a vicinity of critical fields to explain the low-temperature behaviour of specific heat.