Bulk Fermi surface of charge-neutral excitations in SmB6 or not: a heat-transport study

TL;DR

This study uses low-temperature thermal conductivity measurements to investigate whether bulk charge-neutral fermionic excitations, like Majorana fermions, exist in SmB6, providing evidence against their presence.

Contribution

It provides experimental evidence that excludes the existence of bulk charge-neutral fermionic excitations in SmB6, clarifying the nature of quantum oscillations in this material.

Findings

Residual linear thermal conductivity term is zero at zero field.

Thermal conductivity is insensitive to magnetic fields up to 14.5 T.

Results exclude bulk fermionic charge-neutral excitations in SmB6.

Abstract

Recently there have been increasingly hot debates on whether a bulk Fermi surface of charge-neutral excitations exists in the topological Kondo insulator SmB6. To unambiguously resolve this issue, we performed the low-temperature thermal conductivity measurements of a high-quality SmB6 single crystal down to 0.1 K and up to 14.5 T. Our experiments show that the residual linear term of thermal conductivity at zero field is zero, within the experimental accuracy. Furthermore, the thermal conductivity is insensitive to magnetic field up to 14.5 T. These results exclude the existence of fermionic charge-neutral excitations in bulk SmB6, such as scalar Majorana fermions or spinons, thus put a strong constraint on the explanation of the quantum oscillations observed in SmB6.