Eur. Phys. J. B (2014) 87: 97
https://doi.org/10.1140/epjb/e2014-40979-5

Regular Article

Thermoelectric figure of merit in a quantum wire coupled to a graphene sheet between ferromagnetic leads

¹ Department of Physics, Shaoyang University, Shaoyang 422001, P.R. China
² Department of Physics and Key Laboratory for Low-Dimensional Structures and Quantum Manipulation (Ministry of Education), Hunan Normal University, Changsha 410081, P.R. China

^a e-mail: zhoubenhu@163.com

Received: 4 November 2013
Received in final form: 13 February 2014
Published online: 23 April 2014

Abstract

We theoretically investigate the figure of merit ZT for a quantum wire side-coupled by a graphene sheet and sandwiched between two ferromagnetic electrodes with noncollinear magnetic moments. By using the nonequilibrium Green’s function combining with the tight-binding Hamiltonian, we demonstrate that the ZT for the system develops an oscillating behavior and weakly depends on the wire-graphene coupling strength as well as magnetic configuration of the leads. On the contrary, it is strongly dependent on temperature and the polarization strength of the leads. Importantly, the maximum value of ZT for the system without the polarization strength (p = 0) is about 1.1 at temperature k_BT = 0.015Γ₀, which is in agreement with the experimental measurements for silicon nanowires.