Mechanism of Pseudogap in High-Tc Cuprates

1998 ◽  
Vol 12 (29n31) ◽  
pp. 2935-2938
Author(s):  
Fu-Sui Liu

This paper shows that the pseudogap (PG) of Y123 and B2212 is caused by two-local- Cu ++-spin-mediated interaction (TLSMI) in the CuO 2 plane and that PG is a gap of quasiparticle excitation which breaks a Cooper pair without long-range phase coherence.

2001 ◽  
Vol 15 (27) ◽  
pp. 3513-3528 ◽  
Author(s):  
FU-SUI LIU ◽  
WAN-FANG CHEN

This paper extends the two-local-spin-mediated interaction from three- to four-band model, gives two T c formulas using long-range phase coherence condition in quantum and classical XY-models, phase diagram, and types of the gap in Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212). This paper argues that the superconducting gap and the pseudogap are the same gap just at different temperature regions. This paper also argues that the values of T c versus x should be determined by the long-range phase coherence conditions in the classical and quantum XY-model for underdoped and overdoped regions, respectively.


1999 ◽  
Vol 13 (11) ◽  
pp. 1447-1453
Author(s):  
FU-SUI LIU ◽  
WAN-FANG CHEN ◽  
T.-P. CHEN ◽  
J. T. WANG

Taking the two-local-spin-mediated interaction (TLSMI) as the pair potential for the Cooper pair and considering the long-range phase coherence (LRPC), the empirical formula of T c versus hole doping is explained and the physical picture for the pseudogap and the gap in superconductive state is set up. The superconductivity in PrBa 2 Cu 3 O 7-δ and CuCl at high pressure and Fe 1-x S is discussed.


2005 ◽  
Vol 19 (01n03) ◽  
pp. 43-45
Author(s):  
S. DZHUMANOV ◽  
J. D. FAN

It is argued that the new theory that combines the precursor BCS-like non-superconducting (SC) pairing and the Cooper-pair condensation into a superfluid Bose-liquid state is more plausible than the standard SC fluctuation approach in describing the distinctive features of the underdoped and overdoped high-Tc cuprates. We show that the scenarios for high-Tc superconductivity in these materials are quite different on the character of the Cooper-pair formation and SC phase transitions.


Author(s):  
Norman J. Morgenstern Horing

Chapter 13 addresses Bose condensation in superfluids (and superconductors), which involves the field operator ψ‎ having a c-number component (<ψ(x,t)>≠0), challenging number conservation. The nonlinear Gross-Pitaevskii equation is derived for this condensate wave function<ψ>=ψ−ψ˜, facilitating identification of the coherence length and the core region of vortex motion. The noncondensate Green’s function G˜1(1,1′)=−i<(ψ˜(1)ψ˜+(1′))+> and the nonvanishing anomalous correlation function F˜∗(2,1′)=−i<(ψ˜+(2)ψ˜+(1′))+> describe the dynamics and elementary excitations of the non-condensate states and are discussed in conjunction with Landau’s criterion for viscosity. Associated concepts of off-diagonal long-range order and the interpretation of <ψ> as a superfluid order parameter are also introduced. Anderson’s Bose-condensed state, as a phase-coherent wave packet superposition of number states, resolves issues of number conservation. Superconductivity involves bound Cooper pairs of electrons capable of Bose condensation and superfluid behavior. Correspondingly, the two-particle Green’s function has a term involving a product of anomalous bound-Cooper-pair condensate wave functions of the type F(1,2)=−i<(ψ(1)ψ(2))+>≠0, such that G2(1,2;1′,2′)=F(1,2)F+(1′,2′)+G˜2(1,2;1′,2′). Here, G˜2 describes the dynamics/excitations of the non-superfluid-condensate states, while nonvanishing F,F+ represent a phase-coherent wave packet superposition of Cooper-pair number states and off-diagonal long range order. Employing this form of G2 in the G1-equation couples the condensed state with the non-condensate excitations. Taken jointly with the dynamical equation for F(1,2), this leads to the Gorkov equations, encompassing the Bardeen–Cooper–Schrieffer (BCS) energy gap, critical temperature, and Bogoliubov-de Gennes eigenfunction Bogoliubons. Superconductor thermodynamics and critical magnetic field are discussed. For a weak magnetic field, the Gorkov-equations lead to Ginzburg–Landau theory and a nonlinear Schrödinger-like equation for the pair wave function and the associated supercurrent, along with identification of the Cooper pair density. Furthermore, Chapter 13 addresses the apparent lack of gauge invariance of London theory with an elegant variational analysis involving re-gauging the potentials, yielding a manifestly gauge invariant generalization of the London equation. Consistency with the equation of continuity implies the existence of Anderson’s acoustic normal mode, which is supplanted by the plasmon for Coulomb interaction. Type II superconductors and the penetration (and interaction) of quantized magnetic flux lines are also discussed. Finally, Chapter 13 addresses Josephson tunneling between superconductors.


2015 ◽  
Vol 115 (15) ◽  
Author(s):  
B. S. Tao ◽  
H. X. Yang ◽  
Y. L. Zuo ◽  
X. Devaux ◽  
G. Lengaigne ◽  
...  

2005 ◽  
Vol 66 (8-9) ◽  
pp. 1392-1394
Author(s):  
Takashi Yanagisawa ◽  
Mitake Miyazaki ◽  
Kunihiko Yamaji

Sign in / Sign up

Export Citation Format

Share Document