Collective modes and cyclotron resonance in tomographic Fermi liquids

It was predicted recently that 2D electron fluids can host long-lived excitations characterized by odd-parity deformations of the Fermi surface (see [1] and references therein). At low frequencies, these excitations generate multiple viscous modes that propagate over large distances, leading to power-law cascades in both wavenumber and frequency space and giving rise to exotic tomographic hydrodynamics. This talk will discuss the potential for probing these modes through cyclotron resonance experiments, where resonances at multiple cyclotron frequencies excite high-order angular harmonics of the Fermi surface, allowing for the observation of their dynamics. Long-lived odd-parity modes would manifest as higher-order resonances (orders 3, 5, 7,...) with abnormally narrow widths. Due to Kohn's theorem, accessing these higher-order cyclotron resonances requires spatially modulated excitations with nonzero wavenumbers or non-parabolic band dispersion. We present a theory of collective modes that includes Fermi liquid effects in the tomographic regime, linking properties such as mode dispersion and damping to the quantities accessible through cyclotron resonance measurements.

[1] S. Kryhin and L. Levitov, Collinear scattering and long-lived excitations in two-dimensional electron fluids, Phys. Rev. B 107, L201404 (2023).