Structural basis for understanding phase transitions in 3-dimensional charge-density-wave compounds

• Applicant: Professor Dr. Sander van Smaalen
• Subject Area: Mineralogy, Petrology and Geochemistry
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 265092781

Phase transitions towards charge-density wave (CDW) states are often associated with the low-dimensional character of the electron bands in metallic materials. The CDW phase diagram is not understood for substances without obvious low-dimensional features of their crystal structures and physical properties. The proposed project is concerned with the study of CDW phase transitions in the 3-dimensional CDW compounds Lu2Ir3Si5, NiV2S4 (Cr3S4 structure type) and CuV2S4 (Spinel structure type) by means of temperature-dependent single-crystal X-ray diffraction. An important result of these experiments will be the periodic lattice distortion (PLD) associated with the CDW. The PLD provides conclusive information about the location of the CDW within the unit cell of the crystal structure, about the importance of frustrated interactions, about the symmetry (1-q or 2-q state) of the CDW, and about the phonons that may participate in the stabilisation of the CDW state. Diffraction experiments will also be used for analysing further phase transitions (for example a possible occurrence of a lock-in transition) and for the determination of the temperature dependence of the order parameter. The experimental information will be used for theoretical considerations towards understanding the mechanism of the phase transitions and explaining the nature of the physical properties within the CDW state.

• DFG Programme: Research Grants