Sensitive spin-polarization effects in an Aharonov-Bohm double quantum dot ring

Abstract

We study spin-dependent transport and spin polarization through two asymmetric quantum dots (QD’s) embedded in the arms of an Aharonov-Bohm (AB) ring, in which spin splitting produced by external magnetic fields is incorporated into a tight-binding model Hamiltonian. This device shows a sensitive spin-polarization effect by manipulating either in-plane or perpendicular magnetic fields. In particular, an extremely small Zeeman splitting leads to a reversal of the polarization polarity in the differential weighted spin-polarization function. Finally, we demonstrate that the degree of spin polarization is affected by the additional AB effects in the ring. In comparison, the polarization is substantially lower through a single QD in a one-dimensional system.

Lead position and lead-ring coupling effects on the spin-dependent transport properties in a two-dimensional network of quantum nanorings in the presence of Rashba spin–orbit interaction

“…6, 7 and 8 are periodic functions with respect to ka and which are revealed in Eqs. (8), (9), (10), (11) and (12). We find that the periodicity of these figures strongly depends on the geometry of the network due to the number of rings and lead positions.…”

“…Moreover, it can be shown that the periodicity of these figures is independent of lead-ring coupling strength by using Eqs. (8), (9), (10), (11) and (12).…”

“…These quantum interference effects have been intensely probed and explored in multiply-connected domains (e.g., closed single-quantum rings [5] and open single quantum rings with two [6], three [7] and/or multi [8]-attached terminals). The investigation into single quantum rings in the presence of RSOI and/or AB effect has led to the proposal of spintronic devices such as a qubit quantum gate [9,10], spin polarizer [11,12], spin switch [13], spin filter [6,14] and Zeeman splitter [15]. We consider some of these leading works in the following.…”

Transmission through multiple nanoscale rings with Zeeman-split quantum dots

“…Further, our recently investigated results on sharpened AB oscillations [3], and reversal of spin polarization due a small Zeeman splitting [4] for parallel double QD's in resonance suggest the applicability of such structures in the growing field of spintronics [5].…”

Electrostatic control over polarized currents through the spin-orbital Kondo effect

“…To achieve easier integration with current technology, the use of semiconducting lateral single quantum dots (QD) has been suggested as a means to produce spin filtering and spin memory devices [2], which can be controlled through the use of electrostatic gates, without the need of ferromagnetic contacts, nor highly inhomogeneous static magnetic fields, or AC fields. Its experimental realization [3], using a single QD and a large magnetic field to produce a bipolar electrically tunable spin filter, has spurred a multitude of proposals, e.g., two QDs embedded in an Aharonov-Bohm ring [4], a double QD (DQD) in parallel [5], or in a T-shape geometry [6], to cite a few. More related to the results presented here, Borda et al [7] suggested the possibility of spin-filtering in a DQD device at quarter-filling, by exploiting spin and orbital degrees of freedom simultaneously through an SU(4) Kondo state.…”