First-Principles Calculation of Copper Oxide Superconductors That Supports the Kamimura-Suwa Model

Hiroshi Kamimura,Masaaki Araidai,Kunio Ishida,Jaw-Shen Tsai,Shunichi Matsuno,Hideaki Sakata,Osamu Sugino,Kenji Shiraishi

doi:10.3390/condmat5040069

Abstract

In 1986 Bednorz and Műller discovered high temperature superconductivity in copper oxides by chemically doping holes into La2CuO4 (LCO), the antiferromagnetic insulator. Despite intense experimental and theoretical research during the past 34 years, no general consensus on the electronic-spin structures and the origin of pseudogap has been obtained. In this circumstance, we performed a first-principles calculation of underdoped cuprate superconductors La2-xSrxCuO4 (LSCO) within the meta-generalized gradient approximation of the density functional theory. Our calculations clarify first the important role of the anti Jahn-Teller (JT) effect, the backward deformation against the JT distortion in La2CuO4 by doping extra holes. The resulting electronic structure agrees with the two-component theory provided by the tight-binding model of Kamimura and Suwa (K-S), which has been also used to elucidate the d-wave superconductivity. Our first-principles calculation thus justifies the K-S model and demonstrates advanced understanding of cuprates. For example, the remarkable feature of our calculations is the appearance of the spin-polarized band with a nearly flat-band character, showing the peaky nature in the density of states at the Fermi level.

Highlights

On the left side of the figure, a hole occupying a*1g orbital (red arrow) aligns its spin in parallel to the up spin of a localized hole occupying the b*1g orbital (green arrow) to form 3B1g, owing to the Hund’s coupling exchange interaction with the coupling constant, Ka1g (−2 eV) [16]
The calculated result shows that LCO is the antiferromagnetic insulator
We show that the key points obtained from the first-principles calculations for LSCO agree with thoHseereofwteheshKo–wS tmhaotdtehleskheoywpnoiinntsFoigbutarein4e.dIfnropmartthiceufliarsr,t‐ipt riisnschipolwesnctahlcautltahtieoHnsufnodr ’LsScCoOupalginrege spiwn-ittrhipthleotsienotfhtehKe –KS–mS omdoedl ealgsrheeoswwniitnh Fthigeuarpep4e.aIrnanpcaertoicfualasrp,iint-ipsoslhaoriwzendthbaant dthienHcuupnrda’tsecso. upling spin‐triplet in the Kamimura and Suwa (K–S) model agrees with the appearance of a spin‐polarized band in cuprates

Summary

Introduction

On the left side of the figure, a hole occupying a*1g orbital (red arrow) aligns its spin in parallel to the up spin of a localized hole occupying the b*1g orbital (green arrow) to form 3B1g, owing to the Hund’s coupling exchange interaction with the coupling constant, Ka1g (−2 eV) [16]. The first-principle method of the constrained-and-appropriately normed (SCAN) density functional was adopted to calculate a non-rigid electronic-spin energy bands of LCO and LSCO, following Furness et al [19].

Results

Conclusion