單苯環分子接面電流的量子干涉效應

Abstract

本研究以第一原理的計算方法研究單苯環分子接面的電子結構、電子傳輸性質與電流的量子噪音( shot noise )。我們先由VASP計算單苯環分子連接到金電極的最穩定結構，並接著以VASP計算得到的電荷密度作為初始的猜想值，在非平衡態密度泛函電子散射理論架構下，藉由Lippmann-Schwinger equation自洽運算計算得到得單苯環分子接面在不同偏壓下之散射電子的非平衡態波函數，進而計算單苯環分子接面系統的電子結構和電子的量子傳輸性質，包括態密度(density of states)、電流-電壓特性( I-V characteristics)、電流的量子噪音。由態密度探討電導-電壓特性( C-V characteristics)的轉折點，並分析態密度和電流的無單位量子噪音(dimensionless shot noise or Fano factor值)的關係。其結果並與實驗量測值比較，發現理論計算值和實驗量測值相當吻合。

We investigate electronic structures, electron transport properties, and shot noise in benzene single-molecule junctions by first-principles approaches. Firstly, we relax the structure of a benzene molecule bridging between Au electrodes using VASP. In the framework of density-functional theory coupled to Lippmann-Schwinger equation in scattering approaches, we obtain non-equilibrium wave functions self-consistently with the charge-density obtained by VASP as the initial guess. The current-carrying wave functions are applied to calculate the density of states, I-V characteristic, and shot noise of the benzene single-molecule junctions. We investigate the turning points of C-V characteristics and dimensionless shot noise (Fano factor) in relation to density of states. Finally, we compare our theoretical results with recent experimental measurement and find good agreement.