Non-equilibrium and non-homogeneous phenomena around a first-order quantum phase transition

TL;DR

This paper investigates non-equilibrium and surface phenomena around a first-order quantum phase transition using a quantum Ising model, revealing metastability, phase coexistence, and surface wetting effects at zero temperature.

Contribution

It introduces a simple, exactly solvable model to study non-equilibrium dynamics and surface effects in first-order quantum phase transitions, highlighting metastability and wetting phenomena.

Findings

Metastable phases can persist in the coexistence region during quantum quenches.

Surface wetting layers can form at zero temperature due to phase coexistence.

The model demonstrates the role of inhomogeneities and fluctuations in quantum surface phenomena.

Abstract

We consider non-equilibrium phenomena in a very simple model that displays a zero-temperature first-order phase transition. The quantum Ising model with a four-spin exchange is adopted as a general representative of first-order quantum phase transitions that belong to the Ising universality class, such as for instance the order-disorder ferroelectric transitions, and possibly first-order T = 0 Mott transitions. In particular, we address quantum quenches in the exactly solvable limit of infinite connectivity and show that, within the coexistence region around the transition, the system can remain trapped in a metastable phase, as long as it is spatially homogeneous so that nucleation can be ignored. Motivated by the physics of nucleation, we then study in the same model static but inhomogeneous phenomena that take place at surfaces and interfaces. The first order nature implies that both phases remain locally stable across the transition, and with that the possibility of a metastable wetting layer showing up at the surface of the stable phase, even at T=0. We use mean-field theory plus quantum fluctuations in the harmonic approximation to study quantum surface wetting.