A signature for the Luttinger liquid phase in alternating Heisenberg spin-1/2 chains

TL;DR

This paper investigates the low-temperature phases of alternating Heisenberg spin-1/2 chains in a transverse magnetic field, identifying a signature of the gapless Luttinger liquid phase through a new order parameter and specific heat features.

Contribution

The study introduces a novel order parameter to distinguish the Luttinger liquid phase and combines analytical and numerical methods for comprehensive analysis.

Findings

Identification of a double peak structure in specific heat near quantum critical points

Confirmation of the Luttinger liquid phase through the new order parameter

Comparison between analytical spinless fermion approach and Lanczos diagonalization results

Abstract

We have studied the zero and low-temperature behavior of anisotropic alternating antiferromagnetic-ferromagnetic Heisenberg spin-1/2 chains in a transverse magnetic field. Using the analytical spinless fermion approach, the thermodynamic behavior of the model has been studied. We have introduced a new order parameter to distinguish the gapless Luttinger liquid phase from the other gapped phases. The exact diagonalization Lanczos results are also used to compare with the spinless fermion ones. We have found a double peak structure in the specific heat curves for the region between the two quantum critical points. Using the numerical full diagonalization results, the existence of the double peak structure is confirmed.