Pseudospin modulation in coupled graphene systems

The ability to manipulate pseudospin can find applications in Dirac-material based spintronics. Unlike the transport of real spin that can be modulated by a magnetic field, some form of magnetization, or a spin-transfer torque, pseudospin does not respond to a magnetic field, making modulating pseudospin transport a challenging task. We articulate an asymmetrically coupled cavity-waveguide configuration in graphene and uncover a phenomenon: Making the classical dynamics of the cavity deformed can effectively modulate and enhance pseudospin polarization in the waveguide. The underlying mechanism of this remarkable phenomenon can be attributed to chaos-assisted tunneling, which has been well documented in nonrelativistic quantum systems but not yet in Dirac material systems. The finding establishes the feasibility to develop pseudospin modulators for graphene systems through externally applied electrical potential only, with fidelity over 10% at the effective distance of several cavity sizes along the waveguide.