Magnetic and Critical Properties of Alternating Spin Chain with S=1/2,1 in Magnetic Fields

TL;DR

This paper investigates an integrable alternating spin chain with spins 1/2 and 1 under magnetic fields, revealing critical behavior, phase transitions, and conformal field theory descriptions of low-energy excitations.

Contribution

It provides an exact Bethe ansatz solution for the model, analyzes its critical properties, and identifies different conformal field theories governing its low-energy behavior.

Findings

Magnetization exhibits a cusp at a critical magnetic field H=H_C.

Specific heat diverges at H=H_C.

Low-energy spectrum described by two c=1 U(1) CFTs below H_C and one above.

Abstract

We study an integrable spin chain with an alternating array of spins S=1/2, 1 in external magnetic fields using the Bethe ansatz exact solution. The calculated magnetization possesses a cusp structure at a critical magnetic field H=H_{C}, at which the specific heat shows a divergence property. We also calculate finite-size corrections to the energy spectrum, and obtain the critical exponents of correlation functions with the use of conformal field theory (CFT). Low-energy properties of the model are described by two c=1 U(1) CFTs in H<H_{C} and one c=1 U(1) CFT in H>H_{C}.