Pseudospin Valve in Bilayer Graphene: Towards Graphene-Based Pseudospintronics

We propose a nonmagnetic, pseudospin-based version of a spin valve, in which the pseudospin polarization in neighboring regions of a graphene bilayer is controlled by external gates. Numerical calculations demonstrate a large on-off ratio of such a device. This finding holds promise for the realization of pseudospintronics: a form of electronics based upon the manipulation of pseudospin analogous to the control of physical spin in spintronics applications.

Figure 1

Pseudospin-valve effect in bilayer graphene. Schematic diagram of a pseudospin valve in bilayer graphene in its antiparallel (AP) configuration.

Figure 2

Schematical illustration of a pseudospin-valve transistor. This device is operated by switching the polarity of a central gate of length $l$ (shown is the antiparallel configuration).

Figure 3

Pseudo-magnetoresistance ratio $\mathrm{PMR}=(R_{\mathrm{AP}}-R_P)/R_{\mathrm{AP}}$ of the pseudospin valve (where $P$ refers to the parallel configuration) versus the Fermi level of incoming electrons for $d=50a$ (solid curve). Here, $U_0=0.07\mathrm{eV}$ is the magnitude of the gate potential at large distances. The dashed curve refers to the pseudospin-valve transistor shown in Fig. 2, with $l=50a$. Inset: Conductance versus Fermi energy in the antiparallel (solid and dashed curves) and parallel (dotted curve) configurations from which the PMR is derived. The normalization factor is $G_P(E_F=U_0)=4U_{0}W/(3\pi a{\gamma }_0)$.

Figure 4

Pseudo-magnetoresistance ratio of the pseudospin valve (solid curve) and the pseudospin-valve transistor (dashed curve) as a function of the sharpness $d$ of the interface between regions of different polarity. The Fermi energy is set to $E_F=U_0=0.07\mathrm{eV}$.