Quantum-Mechanically Induced Asymmetry in the Phase Diagrams of Spin-Glass Systems

TL;DR

This study uses renormalization-group theory to analyze the quantum Heisenberg model across dimensions, revealing asymmetric phase diagrams and a new multicritical point, with no spin-glass phase observed.

Contribution

It provides a comprehensive analysis of quantum spin-glass systems in all dimensions, highlighting asymmetries and phase boundaries not previously characterized.

Findings

Asymmetric phase diagrams in temperature and bond probability for d ≥ 3

Existence of a multicritical point in d ≥ 6

No spin-glass phase in any dimension

Abstract

The spin-1/2 quantum Heisenberg model is studied in all spatial dimensions d by renormalization-group theory. Strongly asymmetric phase diagrams in temperature and antiferromagnetic bond probability p are obtained in dimensions d \geq 3. The asymmetry at high temperatures approaching the pure ferromagnetic and antiferromagnetic systems disappears as d is increased. However, the asymmetry at low but finite temperatures remains in all dimensions, with the antiferromagnetic phase receding to the ferromagnetic phase. A finite-temperature second-order phase boundary directly between the ferromagnetic and antiferromagnetic phases occurs in d \geq 6, resulting in a new multicritical point at its meeting with the boundaries to the paramagnetic phase. In d=3,4,5, a paramagnetic phase reaching zero temperature intervenes asymmetrically between the ferromagnetic and reentrant antiferromagnetic phases. There is no spin-glass phase in any dimension.