Effect of Cu intercalation and pressure on excitonic interaction in 1T-TiSe2

Article

关键词: CHARGE-DENSITY WAVES;    SUPERLATTICE FORMATION;    LATTICE INSTABILITY;    X-RAY;    SUPERCONDUCTIVITY;    TRANSITION;    SYSTEM;    STATE;    PHASE;   

DOI  :  10.1103/PhysRevB.99.104109

来源: SCIE

【 摘 要 】

1T-TiSe2 has a semimetallic band structure at room temperature and undergoes phase transition to a triple-q charge-density wave (CDW) state with a commensurate superlattice structure (2a x 2a x 2c) below T-c approximate to 200 K at ambient pressure. This phase transition is caused by cooperative phenomena involving electron-phonon and electron-hole (excitonic) interactions, and cannot be described by a standard CDW framework. By Cu intercalation or the application of pressure, this phase-transition temperature is suppressed and superconductivity (SC) appears. However, it is not clear what kind of order parameters are affected by these two procedures. We investigated the crystal structure of CuxTiSe2 and pressurized 1T-TiSe2 around the SC state by synchrotron x-ray diffraction on single crystals. In the high-temperature phase, the variations of structural parameters for the case of Cu intercalation and application of pressure are considerably different. Moreover, the relationship between the critical points of the CDW phase transition and the SC dome are also different for the two cases. The excitonic interaction appears to play an important role in the P-T phase diagram of 1T-TiSe2, but not in the x-T phase diagram.

【 授权许可】

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