Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 54: Correlated Electrons: Charge Order

TT 54.9: Talk

Friday, March 21, 2025, 11:45–12:00, H33

Disorder in Photoexcited Charge Density Wave Systems: Insights from Stochastic Resonance in Impurity Models. — •Francesco Valiera and Martin Eckstein — Department of Physics, University of Hamburg, D-22607 Hamburg, Germany

Photoexcitation in charge density wave (CDW) systems can potentially lead to inhomogeneously disordered phases [1], where ions are displaced locally but do not achieve global ordering. In these phases, each ion moves within a local double-well potential and settles in one of the two equilibrium positions with equal probability. Similar behaviours have also been observed experimentally in VO₂ through scattering experiments [2]. A fundamental question in understanding these disordered states is identifying their signatures beyond X-ray scattering. In order to explore this, we have developed a model of a single ion embedded in a metallic host and use the semiclassical stochastic approach [3] to compute its linear response to an external probe. At low frequencies, the system exhibits a peak in the response amplitude as a function of temperature, which we attribute to stochastic resonance. The latter is typical of bistable systems that experience both periodic driving and noise and it can provide insights into the features of the local double-well potentials and the fluctuations to which the ions are subject.

[1] A. Picano et al., Phys. Rev. B 107, 245112 (2023);

[2] S. Wall et al., Science 362, 572 (2018);

[3] A. Picano et al., Phys. Rev. B 108, 035115 (2023).

Keywords: Charge-density-wave; Photoexcited states; Disordered phases; Quantum dynamics; Stochastic methods