Turning a First Order Quantum Phase Transition Continuous by Fluctuations: General Flow Equations and Application to d-Wave Pomeranchuk Instability

TL;DR

This paper develops a renormalization group approach to study quantum phase transitions, showing that fluctuations can turn a first-order transition into a continuous one, exemplified by a nematic transition in 2D electron systems.

Contribution

It introduces general flow equations for order parameter fluctuations near quantum critical points without relying on power series expansions.

Findings

Fluctuations suppress the first-order nature of the nematic transition.

A continuous quantum critical transition can emerge due to fluctuations.

The method applies to cases where traditional expansions are not feasible.

Abstract

We derive renormalization group equations which allow us to treat order parameter fluctuations near quantum phase transitions in cases where an expansion in powers of the order parameter is not possible. As a prototypical application, we analyze the nematic transition driven by a d-wave Pomeranchuk instability in a two-dimensional electron system. We find that order parameter fluctuations suppress the first order character of the nematic transition obtained at low temperatures in mean-field theory, so that a continuous transition leading to quantum criticality can emerge.