The shear sound of 2D metals

Classical liquids have only longitudinal sound waves, in contrast to classical solids which also have transverse sound. Fermi liquids, however, can differ dramatically from classical liquids by developing a sharp transverse sound mode outside of the particle-hole continuum for sufficiently strong interactions. This shear sound mode is unaltered by the presence of Coulomb interactions and might be present in a variety of strongly interacting metals, in particular two-dimensional metals in which the quasiparticle mass is renormalised to be about twice the bare mass. We study this mode within the bosonization description of Landau Fermi liquids by solving for the entire spectrum of coherent and incoherent excitations of a Fermi liquid with non-zero F_0 and F_1 Landau parameters. This is accomplished by mapping the kinetic equation into a 1D non-hermitian tight binding model. We will also discuss potential routes to excite and detect this mode in experiments.