Quantum interface unbinding transitions

TL;DR

This paper explores the nature of interfacial phenomena during quantum phase transitions, revealing surface critical regimes and singularities that extend into finite temperatures and are influenced by bulk and boundary conditions.

Contribution

It introduces a theoretical framework for understanding interfacial quantum criticality and computes the surface phase diagram and critical exponents for dimensions d≥2.

Findings

Identification of interfacial quantum critical regimes below T_c

Derivation of surface phase diagram in d≥2

Calculation of interfacial singularity exponents in d≥3

Abstract

We consider interfacial phenomena accompanying bulk quantum phase transitions in presence of surface fields. On general grounds we argue that the surface contribution to the system free energy involves a line of singularities characteristic of an interfacial phase transition, occurring below the bulk transition temperature T_c down to T=0. This implies the occurrence of an interfacial quantum critical regime extending into finite temperatures and located within the portion of the phase diagram where the bulk is ordered. Even in situations, where the bulk order sets in discontinuously at T=0, the system's behavior at the boundary may be controlled by a divergent length scale if the tricritical temperature is sufficiently low. Relying on an effective interfacial model we compute the surface phase diagram in bulk spatial dimensionality $d\geq 2$ and extract the values of the exponents describing the interfacial singularities in $d\geq 3$.