Regensburg 2025 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 4: Topological Insulators
TT 4.3: Talk
Monday, March 17, 2025, 10:00–10:15, H33
Phonon thermal Hall effect in weakly compensated topological insulators — •Rohit Sharma1, Yongjian Wang1, Yoichi Ando1, Achim Rosch2, and Thomas Lorenz1 — 1II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, Germany — 2Institute for Theoretical Physics, University of Cologne, 50937 Cologne, Germany
The phonon thermal Hall effect has recently been observed in various classes of insulating materials, yet its origin remains unresolved [1-3]. In a series of well-compensated Bi2−xSbxTe3−ySey samples, the thermal Hall conductivity κxy(B) exhibits a linear and negative field dependence, with a thermal Hall ratio κxy/κxx on the order of 10−3, consistent with observations in other insulating materials. Conversely, weakly compensated samples of TlBi0.15Sb0.85Te2 exhibit a nonlinear dependence of κxy(B), with κxy/κxx exceeding 2% across an extended temperature range. The electronic contribution to thermal transport, κxyel = σxyL0T, was calculated using the Wiedemann-Franz law and compared to the measured κxy. Remarkably, the measured κxy is significantly larger than κxyel throughout the temperature range investigated. Possible mechanisms driving the nonlinear κxy(B) and the large thermal Hall ratio in TlBi0.15Sb0.85Te2 will be discussed.
Funded by the DFG via CRC 1238 Projects A04, B01, and C02.
[1] R. Sharma et al., Phys. Rev. B 109, 104304 (2024).
[2] R. Sharma et al., Phys. Rev. B 110, L100301 (2024).
[3] X. Li et al., Nat. Commun.14, 1027 (2023).
Keywords: Phonon thermal Hall effect; Topological insulators