h/(2 pi k_B T).
(An earlier post on this article gives more background).
Here are some of Zaanen's claims:
In fact, according to the laws of quantum physics, it is impossible for any form of matter to dissipate more than these metals do....It is not clear if these statements concern dissipation of the energy of quasi-particles and whether or not they are fermionic.
the laws of quantum physics forbid the dissipation time to be any shorter at a given temperature than it is in the high-temperature superconductors. If the timescale were shorter, the motions in the superfluid would become purely quantum mechanical, like motion at zero temperature, and energy could not be turned into heat. In analogy with gravity, this timescale could be called the 'Planck scale' of dissipation (or 'planckian dissipation').
Furthermore, I can find no reference which supports this claim that "the laws of quantum mechanics" require such a fundamental limit.
It seems to me, if it were true one could not have a electron-phonon system with a dimensionless coupling constant lambda larger than one. [Above the Debye temperature the electron scattering rate (times hbar) is roughly lamba T].
I welcome clarifying comments.