Coulomb-induced instabilities of nodal surfaces

TL;DR

This paper investigates how Coulomb interactions destabilize fermionic nodal surfaces, leading to various emergent quantum phases such as gapped states, inhomogeneous phases, and potential superconductivity, depending on doping and disorder.

Contribution

It reveals the mechanisms by which Coulomb repulsion induces instabilities in nodal surfaces and explores the resulting phase diagram with tunable parameters.

Findings

Nodal surfaces at the Fermi level are gapped by particle-hole order.

Inhomogeneous phases suppress the instability caused by energy dispersion.

Order parameter fluctuations near criticality can induce superconductivity.

Abstract

We consider the stability of nodal surfaces in fermionic band systems with respect to the Coulomb repulsion. It is shown that nodal surfaces at the Fermi level are gapped out at low temperatures due to emergent particle-hole orders. Energy dispersion of the nodal surface suppresses the instability through an inhomogenous phase. We argue that around criticality the order parameter fluctuations can induce superconductivity. We show that by tuning doping and disorder one could access various phases, establishing fermionic nodal surface systems as a versatile platform to study emergent quantum orders.