Probing Fermi surface topology by ultrafast pump pulse dynamics

Debamalya Dutta; Kush Saha

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arXiv · 2508.06910

Probing Fermi surface topology by ultrafast pump pulse dynamics

Debamalya Dutta·Kush Saha

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Abstract

We present a dynamical approach to detect changes in Fermi surface topology in a two-band model. Specifically, we show that the system's response to a low intensity light pulse can precisely identify topological Lifshitz transitions. At a suitable frequency, the light resonantly couples valence and conduction electrons, leading to an oscillation in the interband coherence term. This, in turn, generate a persistent oscillatory current which survives even after the end of the pulse. Notably, the relative amplitude of the oscillatory current during the pulse with that of the post-pulse reaches a minimum when the Fermi energy aligns with the saddle point, providing a robust framework for dynamically identifying Lifshitz transitions.

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Debamalya Dutta, Kush Saha. 2025-08-09. Probing Fermi surface topology by ultrafast pump pulse dynamics. https://arxiv.org/abs/2508.06910

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