Effect of random fluctuations on quantum spin-glass transitions at zero temperature

TL;DR

This paper investigates how random fluctuations influence quantum spin-glass phase transitions at zero temperature, revealing broad energy gap distributions and Griffiths-like effects through analysis of infinite-range models with a transverse field.

Contribution

It demonstrates the impact of sample-to-sample fluctuations on energy gaps and phase transition mechanisms in quantum spin-glass models, highlighting differences between continuous and discontinuous transitions.

Findings

Broad distributions of energy gaps due to fluctuations

Quantum Griffiths-like effects observed in gap distributions

Distinct mechanisms for continuous and discontinuous phase transitions

Abstract

We study the effects of random fluctuations on quantum phase transitions by the energy gap analysis. For the infinite-ranged spin-glass models with a transverse field, we find that a strong sample-to-sample fluctuation effect leads to broad distributions of the energy gap. As a result, the linear, spin-glass, and nonlinear susceptibilities behave differently from each other. The power-law tail of the distribution implies a quantum Griffiths-like effect that could be observed in various random quantum systems. We also discuss the mechanisms of the phase transition in terms of the energy gap by comparing the Sherrington-Kirkpatrick model and random energy model, which demonstrate the difference between the continuous and discontinuous phase transitions.