On the quantum criticality in the ground and the thermal states of XX model

TL;DR

This paper investigates the quantum critical behavior of the XX model's ground and thermal states by analyzing their spectra and eigenstates, revealing insights into quantum phase transitions at different temperatures.

Contribution

It provides a comparative analysis of ground and thermal states in the XX model, highlighting their physical properties related to quantum criticality across temperature regimes.

Findings

Ground and thermal states exhibit distinct critical behaviors.

Spectral analysis reveals differences in quantum phase transition signatures.

Thermal effects modify the critical properties observed at zero temperature.

Abstract

We compare the critical behavior of the ground state and the thermal state of the XX model. We analyze the full energy spectrum and the eigenstates to reconstruct the ground state and the thermally excited state. With the solutions, we discuss about several physical properties of the states, which are related to quantum phase transition, in various limits, at zero temperature as well as at a thermal equilibrium.