Pure spin-current diode based on interacting quantum dot tunneling junction*

Abstract

A magnetic field-controlled spin-current diode is theoretically proposed, which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes. By applying a spin bias V S across the junction, a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists. More interestingly, if we applied an external magnetic field on the quantum dot, we observed a clear asymmetry in the spectrum of spin current I S as a function of spin bias, while the charge current always decays to zero in the Coulomb blockade regime. Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias, while the net charge through the device is almost zero. Different from the traditional charge current diode, this design can change the polarity direction and rectifying ability by adjusting the external magnetic field, which is very convenient. This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.

Controllable spin diode based on a semiconductor quantum dot

“…The polarity direction of the spin diode and spin accumulation in the QD can be controlled in a fully electric manner, which is much more feasible than using a magnetic method, as previously proposed. 11,44,50) The numerical results in this work show that the spin diode device works well over a wide range of parameters and is favourable in lowtemperature conditions.…”

Spin diode and spin valve based on an interacting quantum dot coupled with nonmagnetic electrodes

“…25,26) Moreover, recent studies have even utilized QDs to design diodes that can control spin rather than charge. [27][28][29] In their schemes, almost no charge current can be transported in the device, but the spin current flowing through it exhibits a rectification effect, which is named the "spin-current diode". [30][31][32] We know that diode devices are the most important electronic components of modern integrated circuits.…”

“…A small spin difference Δμ exists between the spin-up and spin-down chemical potentials in the source (S) lead, and a tunable electric bias voltage V e is applied across the junction. Although there have been some studies on the electron transport process in similar structures, [27][28][29][36][37][38][39][40] their main focus was on spin bias rather than electric bias. Our calculation results indicate that (i) without applying an external magnetic field, the current spectrum driven by the electric voltage (V e ) of this device exhibits a significant asymmetric distribution.…”

“…In weakly coupled QD-based junctions, electron transport occurs via sequential charging events rather than a continuous electron flow. 45,46) The evolution of the occupation probabilities of the different states of a QD can be calculated by the rate equation: 20,28,47,48)…”