Electromagnetic response in kinetic energy driven cuprate superconductors: Linear response approach

Abstract

Within the framework of the kinetic energy driven superconductivity, the electromagnetic response in cuprate superconductors is studied in the linear response approach. The kernel of the response function is evaluated and employed to calculate the local magnetic field profile, the magnetic field penetration depth, and the superfluid density, based on the specular reflection model for a purely transverse vector potential. It is shown that the low temperature magnetic field profile follows an exponential decay at the surface, while the magnetic field penetration depth depends linearly on temperature, except for the strong deviation from the linear characteristics at extremely low temperatures. The superfluid density is found to decrease linearly with decreasing doping concentration in the underdoped regime. The problem of gauge invariance is addressed and an approximation for the dressed current vertex, which does not violate local charge conservation is proposed and discussed.

Doping dependence of Meissner effect in cuprate superconductors

“…Our result shows clearly that in low temperature, the magnetic field penetration depth Dk(T) exhibits a linear temperature dependence, however, it crosses over to a nonlinear behavior in the extremely low temperatures, in good agreement with experimental observation in nominally clean crystals of cuprate superconductors [4,[8][9][10]6,7]. In comparison with our previous discussions [20], our present results also show that the good agreement can be reached by introducing the second-nearest neighbors hopping t 0 in the nearest neighbors hopping t-J model. It should be emphasized that the present result for cuprate superconductors is much different from that in the conventional superconductors, where the characteristic feature is the existence of the isotropic energy gap D s , and then Dk(T) exhibits an exponential behavior as Dk(T) / exp(ÀD s /T).…”

“…3 (then Fig. 5), in the present t-t 0 -J model is the same as that in the t-J [20], and can be attributed to the nonlocal effects induced by the gap nodes on the Fermi surface in a pure d-wave pairing state [15][16][17][18][19]. A weak external magnetic field acts on the SC state of cuprate superconductors as a perturbation.…”

Kinetic-energy-driven superconductivity in cuprate superconductors

“…143,157 For the discussions of the doping and temperature dependence of the electromagnetic response, the t-J model (34) can be extended by including the exponential Peierls factors as 135,143,157 …”

“…4.7. In this case, the electron current operator is obtained in terms of the electron polarization operator, which is a summation over all the particles and their positions, and can be expressed explicitly in the fermion-spin representation as 143,157 then the electron current operator 131 is obtained by evaluating the time-derivative of the polarization operator as j = ∂P/∂t = (i/ )[H, P]. In particular, in the linear response approach, this electron current operator is reduced as j = j (d) + j (p) , with the corresponding diamagnetic (d) and paramagnetic (p) components of the electron current operator that are given by 143,157 …”

Doping Dependence of Meissner Effect in Triangular-Lattice Superconductors

“…In this case, we need to impose boundary conditions for charge carriers, which can be done within the simplest specular reflection model 51,52 with a two-dimensional geometry of the SC plane. Following our previous discussions of the electromagnetic response in square-lattice superconductors 23,50 , the local magnetic field profile of triangular-lattice superconductors can be evaluated explicitly as, (34) and then the magnetic-field-penetration depth is obtained from this local-magnetic-field profile as,…”