Electromagnetic-Field-Induced Suppression of Transport through $n\mathrm{\text{−}}p$ Junctions in Graphene

We study electronic transport through an $n\mathrm{\text{−}}p$ junction in graphene irradiated by an electromagnetic field (EF). In the absence of EF one may expect the perfect transmission of quasiparticles flowing perpendicular to the junction. We show that the resonant interaction of propagating quasiparticles with the EF induces a dynamic gap between electron and hole bands in the quasiparticle spectrum of graphene. In this case the strongly suppressed quasiparticle transmission is only possible due to interband tunneling. The effect may be used to control transport properties of diverse structures in graphene, e.g., $n\mathrm{\text{−}}p\mathrm{\text{−}}n$ transistors and quantum dots, by variation of the intensity and frequency of the external radiation.

Figure 1

An $n\mathrm{\text{−}}p$ junction in graphene. The quasiparticle scattering in the absence (dashed lines) and in the presence (solid lines) of the EF is shown.

Figure 2

The CVC of an $n\mathrm{\text{−}}p$ junction, in the presence (solid line) and the absence (dashed line) of EF. It is calculated by using Eqs. (13, 16), and the parameters ${ϵ}_0=0.02\mathrm{eV}$, $d=1\mu \mathrm{m}$, $\hslash \omega =(4/3){ϵ}_0$, and $S=1\mathrm{W}/{\mathrm{cm}}^2$.

Figure 3

The phase trajectories $p(x)$ of the Hamiltonian ${\widehat{H}}_{\mathrm{eff}}$ corresponding to various cases of interband tunneling. (a) Tunneling through the dynamic gap ${\Delta }_R$ (thick solid line, the values of parameters were $U=2\mathrm{meV}$ and $\hslash \omega =0.8\mathrm{meV}$); the perfect transmission through the point $p=0$ (gray solid line, $U=2\mathrm{meV}$ and $\hslash \omega =3\mathrm{meV}$). (b) The zero transmission case ($U=1.2\mathrm{meV}$ and $\hslash \omega =0.8\mathrm{meV}$). $d=2\mu \mathrm{m}$, ${ϵ}_0=1\mathrm{meV}$, and ${\Delta }_R=0.2\mathrm{meV}$ were also chosen.