Enhanced spin-dependent thermopower in a double-quantum-dot sandwiched between two-dimensional electron gases**Project supported by the National Natural Science Foundation of China (Grant Nos. 61274101, 51362031, and 11675023), the Innovation Development Fund of China Academy of Engineering Physics (CAEP) (Grant No. ZYCX1921-02), the Presidential Foundation of CAEP (Grant No. YZ2015014), the Initial Project of University of Electronic Science and Technology of China,

Abstract

We study the spin-dependent thermopower in a double-quantum-dot (DQD) embedded between the left and right two-dimensional electron gases (2DEGs) in doped quantum wells under an in-plane magnetic field. When the separation between the DQD is smaller than the Fermi wavelength in the 2DEGs, the asymmetry in the dots’ energy levels leads to pronounced quantum interference effects characterized by the Dicke line-shape of the conductance, which are sensitive to the properties of the 2DEGs. The magnitude of the thermopower, which denotes the generated voltage in response to an infinitesimal temperature difference between the two 2DEGs under vanishing charge current, will be obviously enhanced by the Dicke effect. The application of the in-plane magnetic field results in the polarization of the spin-up and spin-down conductances and thermopowers, and enables an efficient spin-filter device in addition to a tunable pure spin thermopower in the absence of its charge counterpart.