A generalized BEC picture of superconductors

作者：Grether M^*; de Llano M; Tolmachev V V

来源：International Journal of Quantum Chemistry, 2012, 112(18): 3018-3024.

DOI：10.1002/qua.24193

• Cooper pairs
• Base-Einstein condensation
• superconductors
• superfluids

A recent re-examination of BCS theory leads one to devise a generalized BEC formalism (GBEC), that is, essentially a boson-fermion (BF) model containing three new ingredients: (i) Cooper pairs (CPs), in contrast to BCS pairs, as real bosons; (ii) BF vertex interactions (analogous to electron-phonon vertices); and (iii) two-hole CPs (2hCPs) accounted for along with two-electron CPs (2eCPs). In addition to the usual normal phase at high-enough temperatures T, three condensed phases emerge at lower temperatures with substantially higher Tcs than BCS theory. These are: two pure BEC phases of 2eCPs and of 2hCPs as well as a mixed phase with both kinds of CPs. BCS theory is precisely recovered with a mixed phase of equal numbers of both kinds of CPs. In contrast to the well-known BCS exponential rise from zero of Tc as function of carrier-number density the GBEC scheme exhibits the linear rise as function of doping as eminently observed in high-Tc underdoped superconductors such as YBCO.

• 出版日期2012-9-15