Magnetic phase diagram of a quasi-one-dimensional quantum spin system

TL;DR

This paper develops an analytical approach to determine the ordering temperature of quasi-1D antiferromagnetic systems under magnetic fields, highlighting the role of critical exponents and quantum critical points, with results aligning with experimental observations.

Contribution

An analytical ansatz is proposed to calculate the ordering temperature of quasi-1D AF systems in magnetic fields, incorporating critical exponents and quantum critical points.

Findings

Field dependence of critical exponents influences re-entrant phase transitions.

Quantum critical points affect the field dependence of the ordering temperature.

Results qualitatively match experimental observations on quasi-1D AF systems.

Abstract

We propose an analytical ansatz, using which the ordering temperature of a quasi-one-dimensional (quasi-1D) antiferromagnetic (AF) system (weakly coupled quantum spin-1/2 chains) in the presence of the external magnetic field is calculated. The field dependence of the critical exponents for correlation functions of 1D subsystems plays a very important role. It determines the region of possible re-entrant phase transition, governed by the field. It is shown how the quantum critical point between two phases of the 1D subsystem, caused by spin-frustrating next-nearest neighbor (NNN) and multi-spin ring-like exchanges, affects the field dependence of the ordering temperature. Our results qualitatively agree with the features, observed in experiments on quasi-1D AF systems.