Dresden 2026 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 25: f-Electron Systems
TT 25.3: Talk
Tuesday, March 10, 2026, 10:00–10:15, HSZ/0101
Terahertz Signatures of Coupled Topological and Heavy-Fermion States in SmB6 — •Zekai Chen, Debankit Priyadarshi, Erik W. de Vos, and Manfred Fiebig — Department of Materials, ETH Zurich, Zurich, Switzerland.
We present a THz time-domain spectroscopy study that resonantly probes the conducting surface state of the topological Kondo insulator samarium hexaboride (SmB6). Previous work on Kondo insulators has shown that the Kondo quasiparticles disintegrate near a quantum critical point (QCP) following THz radiation, leading to a delayed echo-pulse-like signal in the time domain [1]. In contrast to these materials, SmB6 exhibits an additional in-gap state that is hypothesized to be related to its topological surface conductivity. In the presented experiment, this in-gap state is resonantly probed with THz radiation. Our results show the aforementioned echo-like signal at 3 ps, which matches the theoretical surface Kondo temperature [2]. The link between the topological surface state and the Kondo effect is corroborated by the observation of a transition towards negative optical conductivity of the instantaneous THz reflection, which emerges on the same temperature scale as the echo-response. Our results provide insight into the emergence of a coupling between the in-gap surface state and the underlying correlated Kondo physics in SmB6.
[1] Nature Physics 14, 1103 (2018)
[2] Physical Review Letters, 114, 177202 (2015)
Keywords: Terahertz (THz) spectroscopy; Topological insulators; Kondo effect; Time-domain spectroscopy