Abstract
There have been intense research efforts over the last years focused on understanding the Rashba spin-orbit coupling effect from the perspective of possible spintronics applications. An important component of this line of research is aimed at control and manipulation of electron’s spin degrees of freedom in semiconductor quantum dot devices. A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of a new generation of spintronic devices where control of spin, thus magnetic properties, is achieved via an electric field and not a magnetic field. In this work we investigate theoretically the electron’s spin interference and accumulation process in a Rashba spin-orbit coupled system consisting of a pair of two-dimensional semiconductor quantum dots connected to each other via two conducting semi-circular channels. The strength of the confinement energy on the quantum dots is tuned by gate potentials that allow “leakage” of electrons from one dot to another. While going through the conducting channels, the electrons are spin-orbit coupled to a microscopically generated electric field applied perpendicular to the two-dimensional system. We show that interference of spin wave functions of electrons travelling through the two channels gives rise to interference/conductance patterns that lead to the observation of the geometric Berry’s phase. Achieving a predictable and measurable observation of Berry’s phase allows one to control the spin dynamics of the electrons. It is demonstrated that this system allows use of a microscopically generated electric field to control Berry’s phase, thus, enables one to tune the spin-dependent interference pattern and spintronic properties with no need for injection of spin-polarized electrons.
Highlights
Past advances in the field of nanotechnology have enabled the precise, controlled fabrication of materials at atomic and molecular scales.[1,2] In nanoscale territory, the electron’s quantum mechanical nature dominates with the payoff that electronic devices built on nanoscale show remarkable properties
A promising way to achieve this goal is to make use of the tunable Rashba effect that relies on the spin-orbit interaction in a two-dimensional electron system embedded in a host semiconducting material that lacks inversion-symmetry. This way, the Rashba spin-orbit coupling effect may potentially lead to fabrication of a new generation of spintronic devices where control of spin, magnetic properties, is achieved via an electric field and not a magnetic field
The great interest in 2D semiconductor quantum dot devices stems from the fact that such systems utilize the discreteness of the electron’s charge and spin in a highly tunable way, they offer a possible breakthrough in device/circuit technology.[7,8,9,10,11,12,13,14,15,16]
Summary
Semiconductor quantum dot systems since such phenomena may lead to device applications on the field of spin-based electronics (spintronics).[17,18]. Experiments show that gate-controlled microscopically generated electric fields of this nature are quite strong resulting in measurable SO interaction effects for a variety of systems.[21,22,23] In this work we investigate theoretically the spin interference process in a Rashba SO coupled 2D system of electrons consisting of a pair of 2D semiconductor quantum dots connected to each other via two conducting semi-circular channels This system allows use of a perpendicularly applied microscopically generated electric field in conjunction with a weak perpendicular magnetic field to control the Berry’s phase[24] acquired by the electrons. This way one can tune the spin-dependent interference pattern and spintronic properties of the system with no need for injection of spin-polarized electrons
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