Berlin 2024 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 74: Topological Insulators

TT 74.4: Talk

Thursday, March 21, 2024, 15:45–16:00, H 3005

Optical spectroscopy study of the magnetic topological insulators Mn(Bi_1−xSb_x)₂Te₄ at ambient and high pressure — •M. Köpf¹, S. H. Lee^2,3, Z. Q. Mao^2,3,4, and C. A. Kuntscher¹ — ¹Experimentalphysik II, Institute of Physics, Augsburg University, 86159 Augsburg, Germany — ²2D Crystal Consortium, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania 16802, USA — ³Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA — ⁴Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802, USA

The magnetic topological insulator MnBi₂Te₄ and the related materials Mn(Bi_1−xSb_x)₂Te₄ are promising candidates for the realization of rare quantum mechanical effects due to the coexistence of topological surface states and magnetic ordering. We studied the optical response of Mn(Bi_1−xSb_x)₂Te₄ with various Sb doping levels x at ambient and under hydrostatic pressure. Both Sb doping and pressure application cause strong effects on the electronic band structure, strongly influencing the free charge carrier dynamics, according to infrared reflectivity measurements. In the Sb-doped compounds the metallic strength decreases from x=0 to x=0.26, followed by an increase for higher x. Under hydrostatic pressure, MnBi₂Te₄ and the least metallic material Mn(Bi_0.74Sb_0.26)₂Te₄ (x=0.26) show an unusual decrease in metallic character up to ∼10 GPa.

Keywords: magnetic topological insulator; infrared spectroscopy; high pressure; charge carrier dynamics