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    nanoscience and nanotechnology: small is different

Coherent manipulation of macroscopic phases in quantum materials

Dr Claudio Giannetti
Università Cattolica del Sacro Cuore, Brescia, Italy
Martes, 07 Febrero 2023 12:00


Managing light-matter interaction on timescales faster than the loss of electronic coherence is key for achieving the full quantum control of final products in solid-solid transformations. In this seminar, we discuss the possibility of optically manipulating macroscopic phases in quantum solids.
The first example is the demonstration of coherent electronic control of the photoinduced insulator-to-metal transition in the prototypical Mott insulator V2O3. Selective excitation of a specific interband transition with two phase-locked light pulses manipulates the orbital occupation of the correlated bands in a way that depends on the coherent evolution of the photoinduced superposition of states. Comparison between experimental results and numerical solutions of the optical Bloch equations indicates an electronic coherence time on the order of 5 fs. Temperature dependent experiments suggest that the electronic coherence time is enhanced in the vicinity of the insulator-to-metal transition critical temperature, thus highlighting the role of fluctuations in determining the electronic coherence (arXiv:2211.01735).

As a second example, we discuss the possibility of using artificial lattices made by lead halide perovskite nanocubes as a new platform to simulate and investigate the physics of photoexcited quantum materials. The optical injection of quantum confined excitons plays the role of doping in real materials. At large photo-doping, the exciton gas undergoes an excitonic Mott transition, which fully realizes the magnetic-field-driven insulator-to-metal transition described by the Hubbard model. At lower doping, the long-range interactions drive the formation of a collective superradiant state, in which the phases of the excitons generated in each single perovskite nanocube are coherently locked. The simultaneous control of the local Mott physics and collective orders in a single platform with tunable length scales and disorder opens the way to tackle a broader class of problems. An important example is given by copper-oxides, in which ordered phases, such as superconductivity and charge density waves, emerge from a doped Mott insulating phase.