Kondo Breakdown and Quantum Oscillations in SmB$_6$

TL;DR

This paper explains quantum oscillation phenomena in SmB$_6$ by proposing surface Kondo breakdown and topologically protected surface states, reconciling experimental data with theoretical models.

Contribution

It introduces a novel interpretation involving surface Kondo breakdown and topological surface states to explain quantum oscillations in SmB$_6$.

Findings

Quantum oscillations can originate from surface states in SmB$_6$.

Surface Kondo breakdown explains the low temperature amplitude upturn.

High frequency oscillations are linked to topologically protected orbits.

Abstract

Recent quantum oscillation experiments on SmB$_6$ pose a paradox, for while the angular dependence of the oscillation frequencies suggest a 3D bulk Fermi surface, SmB$_6$ remains robustly insulating to very high magnetic fields. Moreover, a sudden low temperature upturn in the amplitude of the oscillations raises the possibility of quantum criticality. Here we discuss recently proposed mechanisms for this effect, contrasting bulk and surface scenarios. We argue that topological surface states permit us to reconcile the various data with bulk transport and spectroscopy measurements, interpreting the low temperature upturn in the quantum oscillation amplitudes as a result of surface Kondo breakdown and the high frequency oscillations as large topologically protected orbits around the X point. We discuss various predictions that can be used to test this theory.