Pressure-driven electronic topology and structural phase transitions in Bi2Te2.1Se0.9.
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| Title: | Pressure-driven electronic topology and structural phase transitions in Bi2Te2.1Se0.9. |
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| Authors: | Tsai, Yi-Jia1,2 (AUTHOR), Jian, Sheng-Rui3,4 (AUTHOR), Gospodinov, Marin M.5 (AUTHOR), Marinova, Vera6,7 (AUTHOR), Dimitrov, Dimitre Z.5,6,7 (AUTHOR), Zhang, Dong-Zhou8 (AUTHOR), Chuang, Yu-Chun9,10 (AUTHOR), Chen, Yang-Yuan2 (AUTHOR), Ou, Min-Nan1,2 (AUTHOR) oumn@gate.sinica.edu.tw, Juang, Jenh-Yih1,6 (AUTHOR) jyjuang@nycu.edu.tw, Lin, Chih-Ming1 (AUTHOR) cm_lin@phys.nthu.edu.tw |
| Source: | Journal of Physics & Chemistry of Solids. Jun2026, Vol. 213, pN.PAG-N.PAG. 1p. |
| Subjects: | Phase transitions, Charge transfer, Electronic band structure, Bulk modulus, Thermoelectric materials |
| Abstract: | Synchrotron angle-dispersive X-ray diffraction (ADXRD), Raman scattering, and difference-Fourier electron-density mapping were conducted to track a canonical cascade phase transition of R 3 ‾ m → C 2 / m → C 2 / c → I m 3 ‾ m in Bi 2 Te 2.1 Se 0.9 up to 45.0(2) GPa. The phase sequence resembles that reported for the Se-dominant counterpart Bi 2 Se 2.1 Te 0.9 , except that each transition onset is systematically shifted to higher pressures by ∼2-6 GPa, emphasizing the pronounced compositional sensitivity of phase stability in Bi–Te–Se solid solutions. Notably, these structural transformations are preceded by a Lifshitz-type electronic-topological transition (ETT) at ∼2.9 GPa, as evidenced by concurrent anomalies in the A 1 g 2 breathing mode and the axial modulus. This indicates that the ETT is closely linked to pressure-induced carrier redistribution and the accompanying lattice distortion that ultimately drives van der Waals (vdW) gap collapse. Difference-Fourier electron-density mapping further reveals a progressive charge transfer from Bi-6 p states toward antibonding Te/Se-derived states, followed by charge accumulation in interstitial regions that stabilizes the high-pressure cubic network. Equation-of-state fits yield bulk moduli of 32.3 ± 0.1, 77.1 ± 1.4, 233.9 ± 8.8, and 153.1 ± 2.2 GPa for the R 3 ‾ m , C 2 / m , C 2 / c , and I m 3 ‾ m phases, respectively, documenting systematic stiffening upon progressive suppression of vdW-layer compressibility. Increasing Se content stiffens the rhombohedral phonons of parent Bi 2 Te 3 , elevates the Lifshitz pressure, and stabilizes complex nine-/ten-layer polytypes absent in Te-doped Bi 2 Se 3. These elastic, structural, and vibrational benchmarks provide quantitative constraints for modeling lattice dynamics and transport in alloyed Bi-chalcogenides and clarify how targeted substitution modulates the interplay between electronic and structural instabilities under pressure. • Pressure‐induced Rhombohedral.→ Monoclinic → Cubic cascade in Bi 2 Te 2. 1 Se 0. 9 resolved up to 45 GPa. • Early Lifshitz electronic-topological transition at 2.9 GPa precedes lattice collapse. • Difference-Fourier maps reveal Bi-6 p.→ Chalcogen charge transfer that governs phase stability. • Stepwise bulk-modulus rise (32.→ 234 GPa) provides benchmark elastic data for thermoelectric alloy design. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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