Phase Diagrams, Distinct Conformal Anomalies and Thermodynamics of Spin-1 Bond-Alternating Heisenberg Antiferromagnetic Chain in Magnetic Fields

TL;DR

This paper explores the phase diagrams and thermodynamic properties of a spin-1 bond-alternating Heisenberg antiferromagnetic chain under magnetic fields, revealing multiple phases, quantum critical behaviors, and fitting experimental data.

Contribution

It provides a comprehensive analysis of phase diagrams and quantum criticality for the model using advanced numerical methods, including new insights into conformal anomalies and experimental validation.

Findings

Six phases in longitudinal field including singlet dimer and Haldane

Five phases in transverse field including Z2 symmetry breaking

Reentrant magnetization behavior observed

Abstract

The ground state phase diagrams and thermodynamic properties of a spin-1 bond-alternating Heisenberg antiferromagnetic chain with a single-ion anisotropy in longitudinal and transverse magnetic fields are investigated jointly by means of the infinite time evolving block decimation, the linearized tensor renormalization group and the density matrix renormalization group methods. It is found that in the magnetic field-bond alternating ratio plane six phases such as singlet dimer, Haldane, two Tomonaga-Luttinger liquid, 1/2 magnetization plateau and spin polarized phases are identified in a longitudinal field, while in a transverse field there are fives phases including singlet dimer, Haldane, Z$_2$ symmetry breaking, quasi-1/2 magnetization plateau and quasi spin polarized phases. A reentrant behavior of the staggered magnetization in a transverse field is observed. The quantum critical behaviors in longitudinal and transverse magnetic fields are disclosed to fall into different universality classes with corresponding conformal field central charge $c=1$ and 1/2, respectively. The experimental data of the compound NTENP under both longitudinal and transverse magnetic fields are nicely fitted, and the Luttinger liquid behavior of low temperature specific heat experimentally observed is also confirmed.