Quantum mechanics

Character (mathematics)

Theoretical physics

Linguistics

Phase (matter)

Philosophy

Curvature

Quantum phases

Phase transition

Criticality

Nuclear physics

Classical mechanics

Statistical physics

Physics

Divergence (linguistics)

Mathematics

Geometry

Quantum

Gaussian curvature

Quantum phase transition

Dissipative system

Scientific Reports

A novel approach based on the Uhlmann curvature is introduced for the investigation of non-equilibrium steady-state quantum phase transitions (NESS-QPTs). Equilibrium phase transitions fall invariably into two markedly non-overlapping categories: classical phase transitions and quantum phase transitions. NESS-QPTs offer a unique arena where such a distinction fades off. We propose a method to reveal and quantitatively assess the quantum character of such critical phenomena. We apply this tool to a paradigmatic class of lattice fermion systems with local reservoirs, characterised by Gaussian non-equilibrium steady states. The relations between the behaviour of the Uhlmann curvature, the divergence of the correlation length, the character of the criticality and the dissipative gap are demonstrated. We argue that this tool can shade light upon the nature of non equilibrium steady state criticality in particular with regard to the role played by quantum vs classical fluctuations.

Uhlmann curvature in dissipative phase transitions