Nonthermal control of excited quantum materials via laser interaction quench

Chong-Yu Ruan1

1Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

Quantum material systems upon applying ultrashort laser pulses provide a rich platform to access excited material phases and their transformations that are not entirely like their equilibrium counterparts. The addressability and potential controls of metastable or long- trapped out-of-equilibrium phases have motivated interests both for the purposes of understanding the nonequilibrium physics and advancing the quantum technologies.

Thus far, the dynamical spectroscopic probes eminently focus on microscopic electronic and phonon responses. For characterizing the long-range dynamics, such as order parameter fields and fluctuation effects, the ultrafast scattering probes offer direct sensitivity. Bridging the connections between the microscopic dynamics and macroscopic responses is central toward establishing the nonequilibrium physics behind the light-induced phases.

Learning from the quantum gases microscope experiments and the nonequilibrium sciences on atomic and molecular systems, we present a path to understand the nonequilibrium many-body dynamics using excited quantum material phases as a platform. We first highlight the synergies based on phenomenology to identify common open questions and potentially different manifestations in hard condensed matter systems. To this end, we give the basic theoretical framework on describing the non-equilibrium scattering problems and describe how such framework relates to the out-of-equilibrium phenomena.

On the experimental realizations, the focus will be placed on the short-time behaviors mediated by interaction quench. We give effective models outlining the emergences of nonthermal critical points, and hidden phases setting the initial condition for the long-time relaxation dynamics as the system re-establish the thermal states[1]. In particular, the inhomogeneity embedded in the system formation and their impacts on the dynamical evolutions into especially the long-time trapped states stemming from interaction quench are of particular interests.

Following the phenomenology, rich scenarios as those involve competitive broken-symmetry orders, vestigial orders, and the intertwined ground states could be identified, leading to intriguing nonequilibrium phenomena from vacuum- suspended rare-earth tritellurides[2], tantalum disulfides[3] thin films, and vanadium dioxide nanocrystalline materials[4] upon light excitations re-examined in recent experiments.

1. X. Sun, S. Sun, C.-Y. Ruan, Comptes Rendus. Physique, Online first (2021), 1-59 (2021).
2. F. Zhou et al. Nature Communications 12, 566 (2021).
3. T.-R.T. Han et al. Science Advances 1, e1400173 (2015).
4. Z. Tao et al. Scientific Reports 6, 38514 (2016).

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