Spin-dependent transmission through a chain of rings: Influence of a periodically modulated spin–orbit interaction strength or ring radius.

We study ballistic electron transport through a finite chain of quantum circular rings in the presence of spin–orbit interaction of strength α. For a single ring, the transmission and reflection coefficients are obtained analytically and from them the conductance for a chain of rings as a function of α and of the wave vector k of the incident electron. We show that due to destructive spin interferences, the chain can be totally opaque for certain ranges of k, the width of which depends on the value of α. A periodic modulation of the strength α or of the ring radius widens the gaps considerably and produces a nearly binary conductance output. [ABSTRACT FROM AUTHOR]