Structural dynamics in DCNQI salts and transition metal dichalcogenides studied by electron diffraction simulation

[摘要] ENGLISH ABSTRACT:An in-depth understanding of the working principles of and phenomena governing strongly correlatedcondensed matter materials has paved way for technological advancement in electronicsin the recent decades. The discovery and characterisation of many functional materials rangingfrom superconductors to insulators are hinged on the progressive understanding of the drivingmechanisms behind macroscopic properties like superconductivity and magneto-resistance.Stemming from the nature of structural transitions in highly correlated solids and the correspondingabrupt changes in their conductivity or resistivity, various degrees of order parametershave been investigated using different experimental techniques such as angle resolved photoelectronspectroscopy, optical reflectivity measurements, X-ray crystallography and pump-probespectroscopy, among others. One major technique that could be used to gain further understandingof these correlated systems is electron diffraction analysis.In this dissertation, we demonstrate a qualitative working relationship between electrondiffraction simulation and the corresponding X-ray and electron diffraction experiments. Thesestructural analysis techniques are used to investigate metal-insulator structural transitions instrong electron-lattice correlated charge density wave compounds of the radical anion organicmolecular crystals of Cu-DCNQI and two members of transition metal dichalcogenides, namely,4Hb-TaSe2 and 1T-TiSe2 single crystals. This study contributes to the observation and dynamicsof charge density waves on the atomic spatial and temporal resolutions. A systematic analysis ofelectron diffraction patterns obtainable from femtosecond electron diffraction experiments opensup new perspectives on the interpretation of structural evolution in solids.

[发布机构] Stellenbosch University