β Scribed by Laurens Jansen
No coin nor oath required. For personal study only.
Recently, superconductivity under high pressure in lithium, with a Tc as high as 20 K at 48 GPa (480 kbar), as well as a Tc from about 10 to 16 K over a wide range of pressures (23-65 GPa), has been established in almost simultaneous experiments. Thus far, only cesium was known to become superconducting, with a Tc of 1:5 K under a pressure of about 12.5 GPa. The present paper deals with an interpretation of these results. ReΓΏned electron-phonon interactions yield critical temperatures under pressure as high as 60 -80 K in lithium way above experimental results. In the same framework, even at ambient pressure a critical temperature of about 1 K is predicted, whereas experiments fail to observe superconductivity down to at most a few times 10 -3 K. With emphasis on solid Li, we approach this problem adopting an indirect-exchange pairing formalism earlier introduced in (our) many papers on high-and low-Tc materials. This implies that we postulate that Cooper-pair formation can be mediated through electron-pair (antiparallel-spins) density arising from overlapping charge distributions for pairs of atoms ("molecular dimers") formed at high pressures near the Fermi level, signiΓΏcantly enhanced by s-to-p (or s-to-d) transitions of valence electrons. General results are that the critical temperature is strictly zero at ambient pressure, and that a broad pressure region with low and almost constant Tc (because of steeply rising bulk modulus) should be observed, in agreement with experiment. In addition, no signiΓΏcant change of Tc is predicted across the family of alkali metals.
π SIMILAR VOLUMES
A quantitative analysis is presented of experimental pressure and oxygen-doping effects on the critical temperature of HgBa2CuO4+~ over a wide range of 3, covering both under-and overdoped compositions, on the basis of indirect-exchange pairing between conduction electrons via oxygen anions. The res