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The aim of the project is to bring two previously distinct areas together
- the novel and advanced optical methods of Müller matrix metrology with
- the correlation-driven metal-insulator transitions (charge-ordered and Mott insulators).
Charge-order transitions are supposed to be of second order, but strong involvement of the underlying lattice challenges this description. For Mott insulators a first-order phase transition is proposed when the electronic interactions decrease, inferring a range in which spatially separated regions of metallic and insulating states coexists. Hence, the electrodynamics across the transition resembles the statistical phenomena of percolation.
In the framework of the PhD project a novel low-temperature spectroscopic ellipsometric technique will be utilized, which we developed in the field of percolating systems. The Müller matrix contains the entire optical information accessible by a macroscopic measurement, including spatial and temporal fluctuations hidden in the depolarization. Comparing decomposed measured and simulated Müller matrices gives access to these fluctuations. Müller matrix metrology is an advanced method to identify the shape of the metallic regions and their statistical size distribution from the depolarization of the scattered light.
Here we apply Müller matrix spectroscopy to gain information on the microscopic nature of the coexisting phases and their hysteresis. The aim of the project is to elucidate and understand the coexistence regime at the metal-insulator transition in strongly correlated electron systems. The selected materials for this study range from vanadium oxides to organic charge-transfer salts.
Metal-Insulator-Transitions, Optical properties, Müller matrix metrology, Charge-order transitions of second order, Ellipsometry