Fermi Surface Nesting with Heavy Quasiparticles in the Locally Noncentrosymmetric Superconductor CeRh$_2$As$_2$

TL;DR

This study uses high-resolution ARPES to reveal Fermi surface nesting and conduction-$f$ hybridization in CeRh$_2$As$_2$, linking these features to its antiferromagnetic excitations and unconventional superconductivity.

Contribution

It provides the first spectroscopic evidence of Fermi surface nesting and detailed conduction-$f$ hybridization in CeRh$_2$As$_2$, elucidating their roles in its magnetic and superconducting properties.

Findings

Fermi surface exhibits nesting at ({c}/a, {c}/a)

Strong conduction-$f$ hybridization observed

Nesting explains antiferromagnetic excitations

Abstract

The locally noncentrosymmetric heavy fermion superconductor CeRh$_2$As$_2$ has attracted considerable interests due to its rich superconducting phases, accompanied by a quadrupole density wave and pronounced antiferromagnetic excitations. To understand the underlying physics, we here report measurements from high-resolution angle-resolved photoemission. Our results reveal fine splittings of the conduction bands related to the locally noncentrosymmetric structure, as well as a quasi-two-dimensional Fermi surface (FS) with strong $4f$ contributions. The FS exhibits nesting with an in-plane vector $({\pi}/a, {\pi}/a)$, which is facilitated by the van Hove singularity near $\bar X$ that arises from the characteristic conduction-$f$ hybridization. The FS nesting provides a natural explanation for the observed antiferromagnetic excitations at $({\pi}/a, {\pi}/a)$, which could be intimately connected to its unconventional superconductivity. Our experimental results are well supported by density functional theory plus dynamical mean field theory calculations, which can capture the strong correlation effects. Our study not only provides spectroscopic proof of the key factors underlying the field-induced superconducting transition, but also uncovers the critical role of FS nesting and lattice Kondo effect in the intertwined spin and charge fluctuations.