Optimized unconventional superconductivity in a molecular Jahn-Teller metal
Ruth H. Zadik, Yasuhiro Takabayashi, Gyöngyi Klupp, Ross H. Colman, Alexey Y. Ganin, Anton Potočnik, Peter Jeglič, Denis Arčon, Péter Matus, Katalin Kamarás, Yuichi Kasahara, Yoshihiro Iwasa, Andrew N. Fitch, Yasuo Ohishi, Gaston Garbarino, Kenichi Kato, Matthew J. Rosseinsky and Kosmas Prassides
This is a rich system and is summarised in the (temperature vs. volume) phase diagram below. Superconductivity appears in proximity to a Mott (Jahn-Teller) insulator.
The JT metal is a bad metal. The novel signature here is that because the electrons are almost localised on individual molecules there is Jahn-Teller effect. This is seen in the Fano line shape of the associated vibrational spectra.
Aside: I have often wondered about a good theoretical description of the Fano line shape for vibrational spectra in metals because it is quite common in organic charge transfer salts. There is an old theory by Michael Rice. However, it does not even mention Fano.
Yesterday, Darko Tanaskovic brought to my attention a nice paper which explicitly relates the Rice theory, the relevant Feynman diagrams, to the Fano form for the spectral density. (See especially, Section III).
E. Cappelluti, L. Benfatto, M. Manzardo, and A. B. Kuzmenko