Vortex state in d-wave superconductor: A numerical study of local density of states near the surfaces in strongly correlated superconductors

Abstract

The outlines of recent studies, theories and related problems on the t-J model for studying the low energy properties of the quasiparticles in high-T(sub c) superconductors were described. The spatial variations of the LDOS (Local Density Of States) and the pair potential near the surfaces of the d(sub x(exp 2) - y(exp 2))-wave superconductor have been investigated based on the t-J model including the effect of strong correlation. The d-wave superconductivity with short coherent length and the effect of strong correlation was possible to be treated explicitly by using this model. LDOS for various sites near the flat (110) surface were calculated applying the Gutzwiller approximation. It was found that the ZEP (Zero-Energy Peak) of LDOS was split into two at all sites near the surface. The splitting was not visible when J/t was decreased and the amplitude of the induced imaginary component was small. It was clarified that when the amplitude of the induced s-wave component was enhanced with the increase of the magnitude of J, the ZEP of LDOS was split into two.

高温超伝導体における準粒子の低エネルギー特性研究のためのt-J模型に関する最近の研究、理論および関連する問題点の概要を記述した。d(sub x(exp 2)-y(exp 2))-波超伝導体の表面近傍の局所状態密度(LDOS)および対ポテンシャルの空間変動を強相関効果を包含するt-J模型に基づいて検討した。本模型を用いることにより、短コヒーレンス長および強相関効果を有するd-波超伝導性を明快に処理することが可能となった。平面(110)近傍の各種サイトに対するLDOSをGutswiller近似を適用して計算した。LDOSのゼロエネルギーピーク(ZEP)が表面近傍の全てのサイトで2つに分裂することが分かった。分裂はJ/tが減少し、誘導虚数成分の振幅が小さい時には不可視であった。誘導s-波成分の振幅がJ値の増加により増進すると、LDOSのZEPが2つに分裂することが明らかとなった。