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Title: Do two-dimensional Fermi liquids show odd-even tomographic relaxation
Plain: In two dimensions, theory predicts that distortions of the electrons' momentum distribution with odd symmetry decay much more slowly than even ones. This would give a distinct transport regime between ballistic and viscous flow.
Precise: For a 2D Fermi liquid with $T \ll E_{F}$, kinetic theory dominated by head-on collisions predicts that the slowest odd angular harmonics of the distribution relax at rates $\gamma_{\mathrm{odd}} \sim T^{4}$ (up to logarithms), much smaller than the even rates $\gamma_{\mathrm{even}} \sim T^{2}$ (Ledwith, Guo, Levitov 2019). Is this odd-even effect present in real 2D electron systems, and does it produce the predicted scale-dependent viscosity? Answer yes or no, with measured $\gamma_{\mathrm{odd}}/\gamma_{\mathrm{even}}\ \text{versus}\ T$.
Settled by: Separate measurement of odd and even harmonic relaxation rates (high-order cyclotron resonance or flow imaging in channels of varying width) showing the predicted temperature dependence.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: open
Status note: Theory (Nilsson, Gran, Hofmann, PRX 2025) finds only a few long-lived odd-parity modes, persisting to $T = 0.15 T_{\mathrm{F}}$; no direct measurement of $\gamma_{\mathrm{odd}}/\gamma_{\mathrm{even}}$ versus $T$ is established.
Posed since: (empty)