Dresden 2020 – wissenschaftliches Programm
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KFM 4.2: Vortrag
Montag, 16. März 2020, 15:20–15:40, HSZ 105
Strain-Driven Metal-to-Insulator Transition and Charge Ordering in LiV2O4 — Yu-Mi Wu, Ulrike Niemann, Yi Wang, Y. Eren Suyolcu, Minu Kim, Hidenori Takagi, and •Peter A. van Aken — Max Planck Institute for Solid State Research, Stuttgart, Germany
The coupling of local atomic configurations and electronic degrees of freedom plays a fundamental role in understanding metal-insulator transitions and the formation of charge ordering. In particular, such competing interactions become more pronounced in the geometrically frustrated pyrochlore lattice in the spinel structure, due to fluctuations in the charge, spin and orbital channels. By STEM imaging and electron energy-loss spectroscopy, we have investigated mixed-valence spinel LiV2O4 thin films grown on SrTiO3 and MgO (001) substrates. The epitaxial strain strongly affects the spatial configurations of valence states in LiV2O4, and the local valence distributions are resolved at atomic-scale resolution. Two competing phases are detected in the thin films, a metallic charge-disordered heavy-fermion state on SrTiO3 and an insulating charge-ordered state on MgO. Importantly, our result shows that the out-of-plane lattice compression relieves the charge frustration and induces a Verwey-type-like charge-ordering pattern in LiV2O4. This observation provides atomic-scale insight into the strong charge-order correlation and tuneable electronic-phase transitions in related frustrated systems. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No. 823717 - ESTEEM3.