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Title: Understanding the evolution of anomalous anharmonicity in Bi 2 Te 3 - x Se x

The anharmonic effect in thermoelectrics has been a central topic for decades in both condensed matter physics and material science. However, despite the long-believed strong and complex anharmonicity in the Bi 2Te 3-xSe x series, experimental verification of anharmonicity and its evolution with doping remains elusive. We fill this important gap with high-resolution, temperature-dependent Raman spectroscopy in high-quality single crystals of Bi 2Te, Bi 2Te 2Se , and Bi 2Se 3 over the temperature range from 4 to 293 K. Klemens's model was employed to explain the renormalization of their phonon linewidths. The phonon energies of Bi 2Se 3 and Bi 2Te 3 are analyzed in detail from three aspects: lattice expansion, cubic anharmonicity, and quartic anharmonicity. For the first time, we explain the evolution of anharmonicity in various phonon modes and across the series. Lastly, in particular, we find that the interplay between cubic and quartic anharmonicity is governed by their distinct dependence on the phonon density of states, providing insights into anomalous anharmonicity designing of new thermoelectrics.
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [3] ;  [3] ;  [4]
  1. Univ. of Toronto, ON (Canada). Dept. of Physics & Inst. of Optical Sciences
  2. Princeton Univ., NJ (United States). Dept. of Chemistry
  3. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
  4. Boston College, Chestnut Hill, MA (United States). Dept. of Physics
Publication Date:
Report Number(s):
BNL-113904-2017-JA
Journal ID: ISSN 2469-9950; PRBMDO; R&D Project: PO010; KC0201060; TRN: US1702667
Grant/Contract Number:
SC0012704; DMR-1420541; DMR-1410846
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 9; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; Lattice dynamics; Phonons; Optical phonons
OSTI Identifier:
1372431