First and second-order metal-insulator phase transitions and topological aspects of a Hubbard-Rashba system

TL;DR

This paper investigates a Hubbard-Rashba model revealing first and second-order metal-insulator phase transitions, topological properties, and quantum criticality, with implications for Hall conductivity and magnetic phases at zero temperature.

Contribution

It introduces a mean-field approach to analyze phase transitions and topological aspects in a Hubbard-Rashba system, highlighting new quantum critical and topological phenomena.

Findings

First-order phase transition at finite chemical potential

Quantum criticality at zero chemical potential

Quantized Hall conductivity in the insulating phase

Abstract

This paper considers a model consisting of a kinetic term, Rashba spin-orbit coupling and short-range Coulomb interaction at zero-temperature. The Coulomb interaction is decoupled by a mean-field approximation in the spin channel using field theory methods. The results feature a first-order phase transition for any finite value of the chemical potential and quantum criticality for vanishing chemical potential. The Hall conductivity is also computed using Kubo formula in a mean-field effective Hamiltonian. In the limit of infinite mass the kinetic term vanishes and all the phase transitions are of second order, in this case spontaneous symmetry breaking mechanism adds a ferromagnetic metallic phase to the system and features a zero-temperature quantization of the Hall conductivity in the insulating one.