Fate of density waves in the presence of a higher order van Hove singularity

TL;DR

This paper investigates how higher order van Hove singularities influence the stability and critical temperature of spin-density wave phases in quantum materials, revealing significant enhancements due to the singularities.

Contribution

It introduces a renormalization group analysis of the impact of higher order van Hove singularities on density wave phases in two-dimensional materials, highlighting their role in boosting phase transition temperatures.

Findings

HOVHS can significantly increase the critical temperature of spin-density waves.

The phase formation is enhanced by the power-law divergence of the DOS at HOVHS.

Potential implications for materials like Sr$_3$Ru$_2$O$_7$ and transition metal dichalcogenides.

Abstract

Topological transitions in electronic band structures, resulting in van Hove singularities in the density of states, can considerably affect various types of orderings in quantum materials. Regular topological transitions (of neck formation or collapse) lead to a logarithmic divergence of the electronic density of states (DOS) as a function of energy in two-dimensions. In addition to the regular van Hove singularities, there are higher order van Hove singularities (HOVHS) with a power-law divergences in DOS. By employing renormalization group (RG) techniques, we study the fate of a spin-density wave phase formed by nested parts of the Fermi surface, when a HOVHS appears in parallel. We find that the phase formation can be boosted by the presence of the singularity, with the critical temperature increasing by orders of magnitude. We discuss possible applications of our findings to a range of quantum materials such as Sr$_3$Ru$_2$O$_7$, Sr$_2$RuO$_4$ and transition metal dichalcogenides.