Anderson pseudospin and Superradiant Superconductivity revisited

Abstract

Using Anderson pseudospins (Anderson, 1958; Bardeen et al., 1957), I suggested in 2012 (Baskaran, 2012) superradiant superconductivity (SRSC) and related Dicke phenomena in bulk superconductors. It was a response to a report from Cavalleri’s lab (Kaiser et al., 2012; Fausti et al., 2011), of transient room temperature superconductivity in YBCO, when pumped by 20 THz laser pulses. In my minimal model, Anderson pseudospins in k-space in a bulk superconductor were coupled to single polariton mode. The model was adapted to the pseudogap normal state of YBCO to explain observed transient superconductivity. We also pointed out, possibility of other Dicke phenomena, (i) spontaneous superradiance above a critical polariton matter coupling, with no pumping, (ii) enhanced quantum entanglement near the critical coupling and (iii) superfluoresence. Here we revisit our early work. Recent discovery by Ebbesens group (Thomas et al., 2019) of large increase of superconducting Tc from 30 K to 45 K in KC60 via specially designed plasmon–phonon-polariton mode, but with no external pumping seems to be in line with our early prediction. Relevance of SRSC to developments, including other superradiant matters and Higgs Spectroscopy is pointed out.