Spin filtering and thermopower in star coupled quantum dot devices

Abstract

We analyze the linear thermoelectric transport properties of devices with three quantum dots in a star configuration. A central quantum dot is tunnel-coupled to source and drain electrodes and to two additional quantum dots. For a wide range of parameters, in the absence of an external magnetic field, the system is a singular Fermi liquid with a non-analytic behavior of the electric transport properties at low energies. The singular behavior is associated with the development of a ferromagnetic or an underscreened Kondo effect, depending on the parameter regime. A magnetic field drives the system into a regular Fermi liquid regime and leads to a large peak ($\sim k_B/|e|$) in the spin thermopower as a function of the temperature, and to a $\sim 100\%$ spin polarized current for a wide range of parameters due to interference effects. We find a qualitatively equivalent behavior for systems with a larger number of side coupled quantum dots, with the maximum value of the spin thermopower decreasing as the number of side-coupled quantum dots increases.

References in corpus (14)

• The numerical renormalization group method for quantum impurity systems
• Mechanical Control of Spin States in Spin-1 Molecules and the Underscreened Kondo Effect
• Sum-rule Conserving Spectral Functions from the Numerical Renormalization Group
• Giant thermopower and figure of merit in single-molecule devices
• Quantum phase transition in a single-molecule quantum dot
• Thermal Spin-Transfer Torques in Magnetoelectronic Devices
• Thermoelectric transport through strongly correlated quantum dots
• Optimal thermoelectric figure of merit of a molecular junction
• Violation of the Wiedemann-Franz Law in a Single-Electron Transistor
• Strongly correlated regimes in a double quantum-dot device
• Tunneling through triple quantum dots with mirror symmetry
• Thermopower of an SU(4) Kondo resonance under an SU(2) symmetry-breaking field
• Tunable Charge and Spin Seebeck Effects in Magnetic Molecular Junctions
• Comment on: ``Zero temperature conductance of parallel T-shape double quantum dots'' [Physica E 39 (2007) 214, arXiv:0708.1842v1]