Quantum oscillations of the quasiparticle lifetime in a metal

Nico Huber¹, Valentin Leeb^1,2, Andreas Bauer¹, Georg Benka¹, Johannes Knolle^1,3, Christian Pfleiderer^1,2, Marc A. Wilde¹
1 Technical University of Munich (TUM)
2 Munich Center for Quantum Science and Technology (MCQST)
3 Blackett Laboratory, Imperial College London

The low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands in which correlations are usually described by a renormalization of the band properties. Yet, multiple mutually interacting bands are a property of essentially all materials. This raises the question if there are direct spectroscopic signatures of phenomena beyond an effective single-particle, single-band behaviour. I will discuss such a signature in the quantum oscillations (QOs) of the three-dimensional topological semimetal CoSi [1]. First, I will explain its remarkably simple, well understood conventional QO spectrum related to Fermi surface pockets around the R-point [2-4]. Then, I will discuss an additionally detected QO frequency which defies the standard description in two fundamental aspects. First, the oscillation frequency corresponds to the difference of semi-classical quasi-particle (QP) orbits of two bands although the composite orbit is forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50 K - in stark contrast to all other oscillation frequencies - which already vanish below a few K. I will demonstrate that our findings are in excellent agreement with QOs of the QP lifetime involving a finite coupling between the underlying orbits. Finally, I will discuss our findings with respect to further materials featuring unexpected QO frequencies and their possible application as a tool to identify correlation phenomena in two-dimensional materials as well as bulk multiband metals.

[1] N. Huber et al., Nature 621, 276 (2023)
[2] N. Huber et al., Phys. Rev. Lett. 129, 026401 (2022)
[3] C. Guo et al., Nat. Phys. 18, 813 (2022)
[4] M. A. Wilde et al., Nature 594, 374 (2021)

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