Pressure induced topological and structural phase transitions in 1T-TiSe2: a Raman study

• Published in: Journal of physics. Condensed matter Vol. 31; no. 16; p. 165401
• Main Authors: Rajaji, V, Janaky, S, Sarma, Saurav Ch, Peter, Sebastian C, Narayana, Chandrabhas
• Format: Journal Article
• Language: English
• Published: IOP Publishing 24.04.2019
• Subjects: high pressure; Raman spectroscopy; structural phase transition; topological phase transition; transition metal dichalcogenide
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/1361-648X/ab01bb

High pressure Raman spectroscopy studies on 1T-TiSe2 were carried out up to ~20.5 GPa. Based on the anomalies in phonon linewidth (lifetime) and phonon frequency of A1g mode, we observe three transitions at ~2.5 GPa, ~6.0 GPa and ~15 GPa. The transitions at ~2.5 and ~6.0 GPa are the two topological phase transitions consistent with the theoretical prediction by Zhu et al in 1T-TiSe2 under pressure, namely, a topological trivial to non-trivial transition (Z2  =  1) and topological non-trivial to trivial transition (Z2  =  0). The trigonal (1T) phase of TiSe2 is stable up to ~15 GPa beyond which it undergoes structural transition as seen from the appearance of new Raman modes. There is a coexistence of the 1T and the new high-pressure phase up to ~19 GPa. The structural transition is completely reversible as seen from the appearance of 1T phase Raman spectra upon release of the pressure.