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TT: Fachverband Tiefe Temperaturen

TT 36: Topological Insulators

TT 36.4: Talk

Wednesday, March 29, 2023, 15:45–16:00, HSZ 103

Large thermal Hall effect in a disordered topological insulator — •Rohit Sharma, Mahasweta Bagchi, Oliver Breunig, Yoichi Ando, and Thomas Lorenz — II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany

Topological insulators mother compounds (Bi₂Se₃,Bi₂Te₃) are notorious for their high thermoelectric figure of merit and to quantify that, they have been under scrutiny in the past for their longitudinal thermal transport. Surprisingly no attention has been paid on the transverse part of heat transport. Motivated by the recent findings of thermal Hall effect in some oxide and magnetic insulators[1], we have experimentally observed a large thermal Hall effect in disordered topological insulator TlBi_0.15Sb_0.85Te₂[2]. By comparing thermal conductivity κ_xx and thermal Hall effect κ_xy data with the electrical counterparts (σ_xx & σ_xy), we study a possible influence of phonon drag on thermal transport. Electrical hall conductivity (σ_xy) shows multi-band behaviour in the whole temperature range (4-300K). Electronic contribution to thermal transport κ_e was calculated by using Wiedemann-Franz law and then compared with the measured thermal transport data, where it was found that both κ_xx and κ_xy shows phonon dominated behaviour. When compared κ_xy and κ_e, former shows an order of magnitude higher signal then the latter one.Possible reasons for large thermal Hall effect in TlBi_0.15Sb_0.85Te₂ will be discussed.
Funded by the DFG via CRC 1238 Projects A04 and B01
[1] M. Boulanger et al., Nat. Commun. 11, 5325 (2020)
[2] O. Breuning et al., Nat. Commun. 8, 15545 (2017)