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arXiv 0710.5586cond-mat.str-elcond-mat.mes-hall
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金属-莫特绝缘体界面处整流的抑制

Suppression of rectification at metal-Mott-insulator interfaces

Kenji Yonemitsu, Nobuya Maeshima, Tatsuo Hasegawa

摘要:

研究了金属-Mott-绝缘体界面的电荷输运,并与金属-能带-绝缘体界面的电荷输运进行了比较。对于带状绝缘体,已知整流由于肖特基势垒而发生,肖特基势垒由功函数差产生。然而,对于莫特绝缘体,获得了性质上不同的电流-电压特性。理论上,我们对莫特绝缘体采用一维哈伯德模型,并在此基础上附加金属电极的紧束缚模型。肖特基势垒是由泊松方程的一个简化的密度-势关系的解决方案。通过求解含时薛定谔方程计算电流密度。我们主要采用含时的Hartree-Fock近似,也采用小系统的精确多电子波函数进行比较。整流被发现强烈抑制,即使是大的功函数的差异。我们表明它的密切关系的事实,即场效应注入到一维莫特绝缘体是双极的。在实验上,我们制作了准一维有机莫特和带绝缘体的单晶顶部的非对称接触。在金属镁和莫特绝缘(BEDT-TTF)(F $_2$ TCNQ)[BEDT-TTF=双(亚乙基二硫代)四硫富瓦烯,F $_2$ TCNQ= 2,5-二氟四氰基醌二甲烷]之间的界面处,整流被强烈抑制。

英文摘要:

Charge transport through metal-Mott-insulator interfaces is studied and compared with that through metal-band-insulator interfaces. For band insulators, rectification has been known to occur owing to a Schottky barrier, which is produced by the work-function difference. For Mott insulators, however, qualitatively different current-voltage characteristics are obtained. Theoretically, we use the one-dimensional Hubbard model for a Mott insulator and attach to it the tight-binding model for metallic electrodes. A Schottky barrier is introduced by a solution to the Poisson equation with a simplified density-potential relation. The current density is calculated by solving the time-dependent Schrödinger equation. We mainly use the time-dependent Hartree-Fock approximation, and also use exact many-electron wave functions on small systems for comparison. Rectification is found to be strongly suppressed even for large work-function differences. We show its close relationship with the fact that field-effect injections into one-dimensional Mott insulators are ambipolar. Experimentally, we fabricated asymmetric contacts on top of single crystals of quasi-one-dimensional organic Mott and band insulators. Rectification is strongly suppressed at an interface between metallic magnesium and Mott-insulating (BEDT-TTF)(F$_2$TCNQ) [BEDT-TTF=bis(ethylenedithio)tetrathiafulvalene, F$_2$TCNQ=2,5-difluorotetracyanoquinodimethane].

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