Structural dynamics of 1T-TiSe2 using femtosecond electron diffraction

[摘要] ENGLISH ABSTRACT: Trilayered transition metal dichalcogenides such as our sample (1T-TiSe2) have been studiedfor many years as systems with strong electron-electron and electron-phonon correlations.The main attraction to this family of compound is its potential to exhibit ground state phenomenaknown as charge density waves whose detailed physical origin has been controversiallydetermined.In this study, we have used an ultrafast femtosecond laser based on a pump-probe technique,namely ultrafast electron diffraction, to investigate these exotic features associated with thecrystal. A pump laser pulse photo-excites the crystal from its ground state and the probepulse (ultrashort electron pulse) takes the snapshot of the evolution of the lattice generatingan electron diffraction pattern of the crystal. Hence the dynamical structural behaviour canbe observed in time with a subpicosecond temporal resolution. As a hexagonal close-packedstructure, its signature is expected to be seen in the diffraction pattern in both a steady-stateand electron time-resolved femtosecond electron diffraction.In addition, simulations of electron diffractions pattern for room and low temperature structuraldata via a software called Simulation and Analysis of Electron diffraction (SAED) havebeen carried out. Clear signatures of charge density waves were seen at low temperature.

[发布机构] Stellenbosch University