Controlled Modulation of Spin Transport Through an Asymmetric Ring With Spin-Orbit Interaction

Abstract

We present a theoretical study of spin transport through an asymmetry ring in which the Rashba spin-orbit interaction (RSOI) is the dominant spin-splitting mechanism. The left part and the right part of the asymmetry ring have different RSOI coefficients ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> than ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . Using Griffith's boundary conditions, we investigate the influence of RSOI coefficients on the conductance and spin polarization. For typical range of RSOI coefficients, the transmitted conductance is much more strongly dependent on ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> than ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> . While the transmitted spin polarization is strongly influenced by the RSOI strengths of both arms, i.e., ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , this dependence is distinct from that observed in a symmetric ring. By considering both the conductance and spin polarization, we can optimize the RSOI parameters in the ring for different sensor applications. For instance, one can change the spin polarization almost from the full range of 0 to 1, whilst keeping the conductance constant (since ¿ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has little effect on conductance). On the other hand, by varying a%, one can tune the RSOI strengths such that a large change in both conductance and spin polarization can be achieved.