Ultrafast observation of electron hybridization and in-gap states formation in Kondo insulator SmB6

TL;DR

This study uses ultrafast spectroscopy to investigate electron hybridization and in-gap state formation in the topological Kondo insulator SmB6, revealing temperature-dependent electronic dynamics and the emergence of in-gap states.

Contribution

It provides the first ultrafast observation of hybridization gap opening and in-gap state formation in SmB6, highlighting temperature-dependent electron dynamics.

Findings

Discovered the hybridization gap opening at T1=100 K.

Observed in-gap state formation below T2=20 K.

Identified phonon bottleneck effects in carrier relaxation.

Abstract

SmB6 is a promising candidate for topological Kondo insulator. In this letter, we report ultrafast carrier dynamics of SmB6. Two characteristic temperatures: T1=100 K and T2= 20 K are observed. T1 corresponds to the opening of the f-d hybridization gap revealed by an abrupt disappearance of terahertz f-band plasmon oscillations. Between T1 and T2, a phonon bottleneck effect dominates the photocarrier relaxation processes. Below T2, we observe the formation of in-gap states, which are strongly affected by optically injected hot electrons and the transient electron temperature change.