Kinetic-energy-driven superconductivity in cuprate superconductors

Abstract

Superconductivity in cuprate superconductors occurs upon charge-carrier doping Mott insulators, where a central question is what mechanism causes the loss of electrical resistance below the superconducting (SC) transition temperature? In this paper, we attempt to summarize the basic idea of the kinetic-energy-driven SC mechanism in the description of superconductivity in cuprate superconductors. The mechanism of the kinetic-energy-driven superconductivity is purely electronic without phonons, where the charge-carrier pairing interaction in the particle-particle channel arises directly from the kinetic energy by the exchange of spin excitations in the higher powers of the doping concentration. This kinetic-energy-driven d-wave SC-state is controlled by both the SC gap and quasiparticle coherence, which leads to that the maximal SC transition temperature occurs around the optimal doping, and then decreases in both the underdoped and overdoped regimes. In particular, the same charge-carrier interaction mediated by spin excitations that induces the SC-state in the particle-particle channel also generates the normal-state pseudogap state in the particle-hole channel. The normal-state pseudogap crossover temperature is much larger than the SC transition temperature in the underdoped and optimally doped regimes, and then monotonically decreases upon the increase of doping, eventually disappearing together with superconductivity at the end of the SC dome. This kinetic-energy-driven SC mechanism also indicates that the strong * Corresponding author. 1530009-1 Int. J. Mod. Phys. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 08/24/15. For personal use only. S. Feng et al.electron correlation favors superconductivity, since the main ingredient is identified into a charge-carrier pairing mechanism not from the external degree of freedom such as the phonon but rather solely from the internal spin degree of freedom of the electron. The typical properties of cuprate superconductors discussed within the framework of the kinetic-energy-driven SC mechanism are also reviewed. 1530009-2 Int. J. Mod. Phys. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 08/24/15. For personal use only. Kinetic-energy-driven superconductivity in cuprate superconductors Hole doping Temperature T N AF SC T c T* ~ ∆ PG~λ * PG NM 1530009-3 Int. J. Mod. Phys. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 08/24/15. For personal use only. 1530009-4 Int. J. Mod. Phys. B 2015.29. Downloaded from www.worldscientific.com by UNIVERSITY OF CALIFORNIA @ SAN DIEGO on 08/24/15. For personal use only.Kinetic-energy-driven superconductivity in cuprate superconductors singlets would become charged, resulting in a SC-state. The RVB state is fundamentally different from the conventional Néel state in which the doped charge carrier can move freely among the RVB spin liquid and then a better compromise between the charge-carrier kineti...

Spin Fluctuations and High-Temperature Superconductivity in Cuprates

“…However, as in the conventional slave-boson theory the local constraint of no double occupancy cannot be treated rigorously contrary to the HO technique used in our theory. Nevertheless, this approach yields many results such as doping dependence of T c , the normal state pseudogap, electromagnetic response, charge transport which are in a broad agreement with experiments in cuprates [130].…”

High-energy magnetic excitations in cuprate superconductors

“…This t-J model consists of two parts, the kinetic energy part includes the nearest-neighbor (NN) hopping term t and next NN hopping term t ′ , while the magnetic energy part is described by a Heisenberg term with the NN spin-spin AF exchange J. The high complexity in the t-J model comes mainly from the local constraint of no double electron occupancy, i.e., σ C † lσ C lσ ≤ 1, which can be treated properly within the fermion-spin theory, 20,22 where the constrained electron operators C l↑ and C l↓ are decoupled as C l↑ = h † l↑ S − l and C l↓ = h † l↓ S + l , respectively, with the spinful fermion operator h lσ = e −iΦ lσ h l that keeps track of the charge degree of freedom together with some effects of spin configuration rearrangements due to the presence of the doped hole itself (charge carrier), while the spin operator S l represents the spin degree of freedom, then the local constraint of no double electron occupancy is satisfied in analytical calculations. Based on the t-J model in the fermion-spin representation, we have developed a kinetic energy driven SC mechanism, 18-20 where cuprate superconductors involve charge carrier pairs bound together by the exchange of spin excitations, then the electron Cooper pairs originating from charge carrier pairs are due to charge-spin recombination, and they condense to the d-wave SC groundstate.…”

“…Based on the t-J model in the fermion-spin representation, we have developed a kinetic energy driven SC mechanism, 18-20 where cuprate superconductors involve charge carrier pairs bound together by the exchange of spin excitations, then the electron Cooper pairs originating from charge carrier pairs are due to charge-spin recombination, and they condense to the d-wave SC groundstate. In particular, one of the striking features [18][19][20] is that the AFSRO correlations coexist with superconductivity.…”

“…20,23,24 In this case, the dynamical spin response in cuprate superconductors in the SC state has been discussed 21 based on the kinetic energy driven SC mechanism. Following their discussions, the full spin Green's function has been obtained within the framework of the equation of motion method in terms of the collective charge carrier modes in the particle-hole and particle-particle channels as…”

ARPES Autocorrelation in Electron-Doped Cuprate Superconductors

“…where f † lσ (f lσ ) is the creation (annihilation) operator for a hole with spin σ, and then the local constraint of no-zero electron occupancy σ C † lσ C lσ ≥ 1 in the electron representation is replaced by the local constraint of no-double hole occupancy σ f † lσ f lσ ≤ 1 in the hole representation. This local constraint of no-double hole occupancy now can be treat exactly within the CSS fermionspin formalism 23,24 , f l↑ = a † l↑ S − l and f l↓ = a † l↓ S + l , where the spinful fermion operator a lσ = e −iΦ lσ a l carries the charge of the constrained hole together with some effects of spin configuration rearrangements due to the presence of the doped charge carrier itself, while the spin operator S l describes the spin degree of freedom of the constrained hole, and then the local constraint of no-double hole occupancy is satisfied in the actual calculations. In this fermion-spin representation, the t-J model (1) can be expressed as,…”