Bulletin of the American Physical Society
2023 APS March Meeting
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B52: Electronic Structure: Theory and Spectra
11:30 AM–2:18 PM,
Monday, March 6, 2023
Room: Room 308
Sponsoring
Unit:
FIAP
Chair: Guru Khalsa, Cornell University
Abstract: B52.00007 : Structural ordering and IR-active vibrations within Bi2(Te(1-x)Sex)3
12:42 PM–12:54 PM
Presenter:
Craig S Knox
(University of Leeds)
Authors:
Craig S Knox
(University of Leeds)
Matthew Vaughan
(University of Leeds)
Andrew D Burnett
(University Of Leeds)
Mannan Ali
(University Of Leeds)
Satoshi Sasaki
(University of Leeds)
Edmund H Linfield
(University of Leeds)
Alexander G Davies
(University of Leeds)
Joshua R Freeman
(University of Leeds)
We have performed an investigation into the THz conductivity spectra in the ternary alloy Bi2(Te(1-x)Sex)3 as a function of selenium fraction, x, and temperature. The crystal structure of these alloys is built from layers of atoms ordered in the sequence C1-Bi-C2-Bi-C1 (where Cx can be occupied by the chalcogenides). Selenium is more electronegative than tellurium, and so for small x, selenium is found almost exclusively on the C2 sites. This creates an ordered phase of the topological insulator when x=1/3 (i.e most C2 sites are occupied by selenium, and nearly all C1 sites are occupied by tellurium). We find that the reduction in crystalline anharmonicity due to the preferential ordering of the x=1/3 phase of Bi2(Te(1-x)Sex)3 results in the prominent E1u phonon red-shifting on cooling less than the binary Bi2Te3 and Bi2Se3 samples. We also find that the E1u phonon couples to an electronic continuum at low temperatures (T ≤ 40 K), regardless of x in Bi2(Te(1-x)Sex)3 or the mobility of the topological insulator, possibly indicating the presence of protected surface states
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