Fermi surfaces in Kondo insulators

TL;DR

This paper investigates the Fermi surface properties in the Kondo insulator YbB$_{12}$ through quantum oscillation measurements, revealing small heavy Fermi sections and discussing potential exotic quasiparticle origins.

Contribution

It provides the first detailed analysis of quantum oscillations in YbB$_{12}$, highlighting similarities and differences with other Kondo insulators like SmB$_6$, and proposes models for the Fermi surface origin.

Findings

Observation of quantum oscillations in YbB$_{12}$

Identification of small heavy Fermi surface sections

Comparison with Fermi surfaces in SmB$_6$

Abstract

We report magnetic quantum oscillations measured using torque magnetisation in the Kondo insulator YbB$_{12}$ and discuss the potential origin of the underlying Fermi surface. Observed quantum oscillations as well as complementary quantities such as a finite linear specific heat capacity in YbB$_{12}$ exhibit similarities with the Kondo insulator SmB$_6$, yet also crucial differences. Small heavy Fermi sections are observed in YbB$_{12}$ with similarities to the neighbouring heavy fermion semimetallic Fermi surface, in contrast to large light Fermi surface sections in SmB$_6$ which are more similar to the conduction electron Fermi surface. A rich spectrum of theoretical models is suggested to explain the origin across different Kondo insulating families of a bulk Fermi surface potentially from novel itinerant quasiparticles that couple to magnetic fields, yet do not couple to weak DC electric fields.