Validity of the Wiedemann-Franz law in small molecular wires

Article

关键词: ONE-DIMENSIONAL CONDUCTOR;    THERMOELECTRIC-MATERIALS;    QUANTUM TRANSPORT;    SCALING THEORY;    LOCALIZATION;    RESISTANCE;    EFFICIENCY;    DIFFUSION;    ABSENCE;   

DOI  :  10.1103/PhysRevB.86.035433

来源: SCIE

【 摘 要 】

We report our investigations on the finite-size effects of the Lorenz number in a molecular wire. Using Landauer-Buttiker formalism, we find that for sufficiently long wires there are two validity regimes of the Wiedemann-Franz (WF) law, the cotunneling and the sequential tunneling regimes, while in small systems only the first regime survives. We compare our results with the standard Kubo formalism and explain its failure to obtain the WF law in small systems. Furthermore, our studies on exponentially localized disordered wires show that the Lorenz number value L-0 = (pi(2)/3)(k(B)/e)(2) predicted by the WF law is obtained only in the cotunneling regime. Also, the Lorenz number L exhibits a typical distribution at different temperatures corresponding to different tunneling processes. In particular, first-order tunneling results in a low value of L, whereas second-order tunneling recovers the universal value L-0.

【 授权许可】

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