Characteristic features of d pairing in bilayer cuprates under conditions of Peierls instability of the normal phase

Abstract

A system of self-consistent integral equations for the superconducting gap is formulated and solved taking account of the instability of the normal phase of bilayered cuprates against charge-density waves. The critical parameters are calculated as a function of the wave vector, temperature, and doping index. It is found that the region in which superconductivity coexists with d-type charge-density waves depends strongly on the doping index. The effective energy-gap parameter, determined as the interval between the peaks of the density of states, can have a local minimum at temperatures T<T C .

Spin-Freezing Mechanism in Underdoped Superconducting Cuprates

“…It should be noted that the temperature dependence of Cu(2) Knight shift in YBa 2 Cu 4 O 8 , the evolution of the Fermi surface in Bi 2 Sr 2 CaCu 2 O 81y , and the k dependence of the pseudogap in the normal state have been successfully explained [13] in the framework of that model, including the d-wave orbital symmetry of the superconducting state (SC) [14]. The d-wave SC can coexist with extended charge density waves (for short id-CDW) as it was shown in previous works [15,16]. Furthermore, Chakravarty et al [17] have stressed that the corresponding ordered phase is a staggered pattern of orbital currents.…”

Polaron effects on superexchange interaction: Isotope shifts of T N , T c , and T* in layered copper oxides

“…We believe that another and even more important similarity in the dependence of the order parameters of the superconducting and pseudogap phases on the d -type wave vector (that is, cos q x − cos q y ) was explained in its time under the assumption that the transitions to both these phases are associated with short-range potentials [3]. It seems that superexchange interaction, screened Coulomb repulsion, and interaction of holes mediated by optical phonons are the most significant of these.…”

“…First, we emphasize the following important fact. Within the scenario [3], the superconducting transition temperature T C ∼ 2J − G, whereas the characteristic temperature of the pseudogap phase T * ∼ J + G [3,7]. Here, G is the parameter of the screened Coulomb interaction of holes on the nearest copper sites, which partially includes the correction due to interaction mediated by optical phonon modes.…”

“…In the figure, the values of the coefficient α TC = −d ln(T C )/d ln(M ) for the replacement of 16 O with 18 O are plotted as abscissas, and the numbers of holes per one copper site are plotted as ordinates. The symbols in the curve correspond to the points at which the system of self-consistent equations from [3] was solved. Because only the order of magnitude is known for the polaron energies E a and E c , the parameter γ O was normalized in such a way that α TC was equal to 0.1 at the optimal level of doping.…”

“…We identify the pseudogap phase with the phase of sliding charge-density waves. This system was written in detail in [3] and is not given here.…”