## sounds - theory

- https://en.wikipedia.org/wiki/Zero_sound

- [Zero and First Sound in Normal Fermi Systems](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5379/0910.3283.pdf)
Shohei Watabe,1 Aiko Osawa,2 and Tetsuro Nikuni

- https://en.wikipedia.org/wiki/Second_sound

- [absorption of sound in He3](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5381/Absorption-of-Sound-in-Liquid-He3.pdf) Lukyanchuk

nice derivations

- 2021 [Optical signatures of **shear collective modes** in strongly interacting Fermi-liquids](https://arxiv.org/pdf/2003.06619.pdf) D. Valentinis

> ... up to the Fermi surface. As such, it displays rigidity against perturbations. Such rigidity generates Fermi-surface resonances which manifest as longitudinal and transverse collective modes.


## sounds - experiment

- 1966 [zero sound - experiments](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5435/zero%2Bsound.pdf)
$ \frac{Im \omega}{Re \omega} = $ attenuation (Quantum zero sound) dampening by multi-pair excitations for $ \omega > k_b T$.

1996 [Quantum zero sound in helium-3](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5385/qzs.pdf)

1975 [Observation of Transverse Zero Sound in Normal $He^3$ - Pat R. Roach](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5634/PhysRevLett.36.736%2B-%2Btransverse.pdf) 

## more lectures

http://www-thphys.physics.ox.ac.uk/people/SteveSimon/QuantumMatterFullSummer2019.pdf
[Fermi-liquid theory](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5436/chap_fl.pdf) p. 18(302), and nice picture 310
http://eduardo.physics.illinois.edu/phys561/FL.pdf

https://phas.ubc.ca/~berciu/TEACHING/PHYS502/PROJECTS/FeLi.pdf p.4 (typo corrected as $(1+ \frac{F_1}{3})$ in Eqn. 21?)
[Fermi Liquid Theory: Collective Modes](http://www.cmp.caltech.edu/~mcc/Ph127/c/Lecture11.pdf) also p.4