Time-resolved reflectivity and Raman studies of the interplay of electronic orders in Mo8O23

Article

关键词: TRANSITIONS;    CRYSTALS;    DYNAMICS;    PARTICLE;   

DOI  :  10.1103/PhysRevB.99.085101

来源: SCIE

【 摘 要 】

Monoclinic semimetallic Mo8O23 belongs to a multifunctional series of compounds showing multiple ordering phenomena that have not achieved much attention until now. Previous x-ray studies of this compound have revealed an incommensurate ordering transition at T-IC similar to 350 K, followed by a structural transition to commensurate order at T-IC(-C) = 285 K. In addition, an enigmatic resistance maximum is observed at T-el similar to 150 K, whose origin has so far proved elusive Aiming to disentangle these multiple orders we use the polarized transient optical spectroscopy supplemented by Raman spectroscopy to study the electronic relaxation dynamics and lattice vibrational modes in Mo(8)O(23 )single crystals. Remarkably, both the coherent vibrational mode response and single-particle response display extrema of damping/relaxation times close to T-el with the concurrent appearance of new coherent vibrational modes and a characteristic polarization asymmetry which saturates below T-el. The single-particle relaxation data analysis shows the appearance of a temperature-independent gap in the electronic excitation spectrum below T-IC and additional temperature-dependent gap opening near T ei . Concurrently, a low-frequency vibrational mode shows anomalous softening around T-m similar to 200 K, far below T-IC(-C) and T-IC. The observations are interpreted in terms of the appearance of a hidden gapped state below T-el that has so far eluded detection by structural analyses.

【 授权许可】

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