研究目的
To analyze the photoinduced dynamics in a single crystalline NdNiO3 film upon excitation across the electronic gap, specifically investigating the insulator-to-metal transition and melting of charge order, and comparing with manganites for a unified description.
研究成果
The study demonstrates a photoinduced insulator-to-metal transition in NdNiO3 films, with melting of charge order observed through time-resolved techniques. The dynamics are well-described by a time-dependent order parameter model similar to that used for manganites, suggesting a unified description for such phase transitions. This provides insights into the ultrafast control of material properties via photoexcitation.
研究不足
The time resolution in x-ray diffraction experiments was about 700 fs due to jitter between pump and probe pulses, which is lower than the optical cross-correlation of 50 fs. Uncertainties in laser power and beam size measurements could affect fluence comparisons. The model may not fully capture all aspects of phase coexistence or domain effects.
1：Experimental Design and Method Selection:
The study uses a pump-probe approach with time-resolved reflectivity and resonant x-ray diffraction to investigate the photoinduced insulator-to-metal transition in an epitaxially grown NdNiO3 film. The pump pulse is at 800 nm, exciting the electronic system across the gap.
2：Sample Selection and Data Sources:
A 60 nm thick NdNiO3 thin film grown by pulsed laser deposition on a NdGaO3 substrate with (110) surface orientation was used. Characterization was done at the X04SA surface diffraction beamline at the Swiss Light Source.
3：List of Experimental Equipment and Materials:
Equipment includes a regenerative amplifier system seeded by a Ti:S oscillator for pump and probe beams, a cryostat for temperature control, a Ba(BO2)2 crystal for cross-correlation measurement, photodiodes, boxcar integrators, and for x-ray diffraction, beamline 3 of the SACLA free electron laser with KB mirror focusing, Cu (111) analyzer, and YAP detector. Materials include the NdNiO3 film and NdGaO3 substrate.
4：Experimental Procedures and Operational Workflow:
For time-resolved reflectivity, pump and probe beams at 800 nm were focused to specific sizes, with time resolution of about 80 fs, and measurements taken at various temperatures and fluences. For resonant x-ray diffraction, the x-ray energy was set to the Ni K edge, with beam focusing and diffraction intensity measured over time after excitation.
5：Data Analysis Methods:
Data were fitted with exponential models and a time-dependent order parameter model to describe the dynamics, including error function fits for excitation profiles and Landau-like order parameter descriptions.
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