Vortex state in d-wave superconductor: Local density of states around nonuniform d-wave superconducting state

Abstract

The t-J model for the low energy excitations in high-T(sub c) superconductors has been studied. It was clarified that the splitting of the Zero Energy Peak (ZEP) on (110) surface was enhanced as the doping rate and the magnitude of the superexchange J were increased, and that the Local Density Of States (LDOS) was sensitive to the microscopic structures near the surface. The transfer integrals for the next nearest (t') and the third nearest neighbors (t'') have been included to reproduce the shape of the Fermi surface observed in the experiments. The Gutzwiller approximation has been applied to treat the constraint in the extended t-J model. The effective Hamiltonian containing the next and third nearest transfer integrals was described. The LDOS has been calculated at every site using the self consistently determined pair potential. A new superconducting state, having Cooper pairs with finite total momentum between the residual quasi particles near the node of a d(sub (x(exp 2)-y(exp 2))) wave state, has been found in the t-J model within the Gutzwiller approximation. The LDOS near the surface in the d+s wave state has been calculated. It was found that the new state causes a split of the ZEP near a (110) surface. Various features of the LDOS were obtained depending on the shape of the Fermi surface and the geometry of the surfaces.

高温超伝導体の低エネルギー励起に対するt-J模型を研究した。ドープ率および超交換Jの規模が増大されると共に、(110)表面におけるゼロエネルギーピーク(ZEP)の分裂が大きくなること、また、局所状態密度(LDOS)が表面近傍の微視的構造に対して敏感であることが明らかになった。実験で観察したフェルミ面の形状を再現するために第2隣接(t')および第3隣接(t'')に対する伝送積分を含めた。拡張t-J模型における拘束条件を処理するためにGutzwiller近似を適用した。第2および第3隣接伝送積分を含む有効ハミルトニアンを記述した。自己無撞着的に確定した対ポテンシャルを用いて全てのサイトでLDOSを計算した。d(sub (x(exp 2)-y(exp 2)))波状態のノード近傍の残留準粒子の間に有限全運動量を有するクーパ対をもつ新たな超伝導状態をGutzwiller近似内のt-J模型の中に見いだした。d+s波状態の面近傍のLDOSを計算した。新規状態は(110)表面近傍のZEPの分裂を引き起こすことが分かった。フェルミ面の形状と面の幾何学的位置関係を変えて種々の特徴を持つLDOSを求めた。