Description:

Topological insulator (TI) – magnetic insulator (MI) interfaces have been studied under two important perspectives. On one hand, the spin-momentum locked Dirac surface states of the TI have been used as a platform that enables spin-charge conversion [1]. On the other, these structures have been hypothesized to yield a quantized anomalous Hall effect (QAHE) when broken-time-reversal symmetry at the TI surfaces gaps their surface states [2]. In this talk, I will experimentally discuss one reason behind the success of TI-MI interfaces for spintronics and their lacking ability to host a quantized anomalous Hall effect. Through magnetooptical infrared spectroscopy carried out on high mobility (Pb,Sn)Se – EuSe TI-MI heterostructures, we have demonstrated that the magnetic energy gap of topological Dirac surface states remains much smaller than 10meV when they are brought in contact with the magnetic insulator [3]. This narrow energy gap is unfavorable to observe the QAHE [2], but advantageous for devices that require pristine topological surface states to achieve spin-charge conversion and magnetization switching. [1]

[1] H. Wang et al. Phys. Rev. Lett. 117 076601 (2016), H. Wu et al. Nat. Commun., 12 6251 (2021)
[2] C.Z. Chang, P. Wei and J.S. Moodera MRS Bulletin 39 867 (2014)
[3] J. Wang, T. Wang, et al. Communications Physics 6 200 (2023)

Badih Assaf, Assistant Professor, University of Notre Dame

Host: John Ketterson