Quantum Oscillations of the Quasiparticle Lifetime in a Metal

TL;DR

This paper reports the discovery of quantum oscillations in a topological semimetal that challenge traditional theories, revealing new insights into quasiparticle behavior and interactions in metals.

Contribution

It demonstrates the existence of quantum oscillations in quasiparticle lifetime arising from non-linear coupling of electronic orbits, a phenomenon previously unobserved.

Findings

Quantum oscillations correspond to differences in semi-classical quasiparticle orbits.

Oscillations persist above 50K, unlike typical oscillatory components.

Findings align with models of quasiparticle lifetime oscillations due to orbit coupling.

Abstract

Following nearly a century of research, it remains a puzzle that the low-lying excitations of metals are remarkably well explained by effective single-particle theories of non-interacting bands. The abundance of interactions in real materials raises the question of direct spectroscopic signatures of phenomena beyond effective single-particle, single-band behaviour. Here we report the identification of quantum oscillations (QOs) in the three-dimensional topological semimetal CoSi, which defy 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, which are forbidden as half of the trajectory would oppose the Lorentz force. Second, the oscillations exist up to above 50K - in stark contrast to all other oscillatory components - which vanish below a few K. Our findings are in excellent agreement with generic model calculations of QOs of the QP lifetime. Since the only precondition for their existence is a non-linear coupling of at least two electronic orbits, e.g., due to QP scattering on defects or collective excitations, such QOs of the QP lifetime are generic for any metal featuring Landau quantization with multiple orbits. They are consistent with certain frequencies in topological semi-metals, unconventional superconductors, rare-earth compounds, and Rashba-systems, and permit to identify and gauge correlation phenomena, e.g., in two-dimensional materials and multiband metals.