Nature of high-temperature superconductivity

Abstract

Evidence is presented that the superconducting hole condensate generally does not reside in the cuprate planes of high-temperature superconductors, but in the SrO layers, in the BaO layers, or in the regions of interstitial oxygen. Evidence that electrons, not holes, transfer to the cuprate planes of HgBa2Can−1CunO2+n+δ as a function of pressure, number n of layers, and increasing Tc is presented; holes transfer to the BaO layers. The hole transfer in YBa2Cu3O7 is also to the BaO layers. PrBa2Cu3O7 superconducts (as predicted) when it is free of pair-breaking PrBa defects in its BaO layers. The chosen locus of the superconductivity is consistent with the observation of magnetism in both the CuO layers and the cuprate planes of YBa2Cu3O7. Four materials were successfully predicted to superconduct by assuming that the cuprate planes are normal. There are no n-type high-temperature superconductors; Nd2−zCezCuO4 is p type and doped with interstitial oxygen. When Y+3 is replaced by Am+4, Pb2Sr2YCu3O8 becomes n type and stops superconducting. Holes remain near interstitial oxygen in Tl2Ba2Can−1CunO2n+4+δ. Gd2−zCezCuO4, unlike Nd2−zCezCuO4, does not superconduct because Gd has L=0 and J≠0 and breaks Cooper pairs associated with its interstitial oxygen, but Gd2−zCezSr2Cu2NbO10 does superconduct (in its SrO layers). YBa2Cu3O7 exhibits bulk nodeless (s-wave) superconductivity. We argue that the superconductivity of YBa2Cu3O7 is representative of high-Tc superconductors. The pairing mechanism is electronic (not phononic) and associated with holes on certain oxygen ions (or sulfur ions, in the case of some organic superconductors). We explore a Bardeen-Cooper-Schrieffer-type formalism applied to cuprates, ruthenates, and other compounds.

Theory of high-TCsuperconductivity: transition temperature

“…In the case of YBa 2 Cu 3 O 7-δ it has been proposed that the locus of the holes is in the type I (BaO-CuO-BaO) layers [126]. This is based on bond-valence sum considerations of the type I and II structure properties [127][128][129][130], observed destruction of superconductivity for rare earths substituting for Ba in YBa 2 Cu 3 O 7-δ [5,131], the transfer of electrons away from the type I structures in underdoped YBa 2 Cu 3 O 7-δ [51], differing manifestations of pairing state symmetries [132,133], the nonrequirement of CuO 2 planes for superconductivity [2,134] 31 , 31 Early papers advocating the BaO layers as the locus of the superconducting hole condensate in the cuprates did not include possible superconductivity of the CuO 2 planes. and conversion to the non-superconducting n-type with quadrivalent substitution for Y +3 [127].…”

Carrier transport through a dry-etched InP-based two-dimensional photonic crystal

“…3͑b͒ and 4͑b͒, the conductance of the PhC field ⌺ PhC obtained as 1 / R PhC is plotted in Fig. [25][26][27] As seen in the figure, the simulated conductance scales linearly with the interhole distance l. The intercept on the y axis ⌺ 0 obtained by extrapolation ͑dashed line͒ of the simulated conductance gives the conductance contribution corresponding to the remnant volume V 0 of the material when the holes touch each other ͑i.e., l =0͒.…”

High-Temperature Superconductivity Without Cuprate Planes

“…The locus of superconductivity is in the BaO layers of YBa 2 Cu 3 O 7 [13], PrBa 2 Cu 3 O 7 [14], and the HgBa 2 Ca n−1 Cu n O 2n+2 compounds [14,15]. Some high-temperature superconductors are based on interstitial oxygen, notably Nd 2−z Ce z CuO 4 [12] and T 2 Ba 2 Ca n−1 Cu n O 2n+4 [15], or on S in organic compounds such as κ-[BEDT-TTF] 2 Cu[NCS] 2 [16]. We know of no solid whose superconductivity resides in its cuprate-planes-although most workers in the field believe that it is the cuprate planes that superconduct.…”