Laser-induced modulation of conductance in graphene with magnetic barriers

Abstract

We study how electrons move across a graphene sheet when it encounters two magnetic barriers with a region in between that is continuously driven by laser light. Rather than acting as a static obstacle, this illuminated middle section becomes a Floquet cavity that opens new transport channels through controlled photon absorption and emission. By combining Floquet theory with the transfer matrix method, we track electron transmission through both the main energy band and the emerging photon-assisted sidebands. We find that the laser does more than modify the potential--it reshapes how electrons interact between the magnetic barriers, enabling a switch from ordinary transmission to transport dominated by photon exchange. Because the magnetic field and the optical drive are applied to separate sections of the device, the system supports interference between cyclotron-filtered motion and discrete photon-pumping channels, producing Fano resonances and angle-dependent transmission zeros that cannot appear in double magnetic or double laser barrier systems alone. Under well-defined conditions, the distance between the magnetic barriers controls the coupling between Floquet channels, allowing highly tunable resonances and even perfect transmission, despite strong magnetic confinement. We also observe that low-energy carriers are efficiently blocked by the magnetic regions, while conductance steadily rises with energy until it reaches a clear saturation plateau. This hybrid design provides a versatile way to steer graphene electrons by balancing optical pumping and magnetic momentum filtering.

Figures (8)

• Figure 1: Schematic of a graphene sheet divided into 5 regions, where regions 1 and 3 are controlled by two magnetic fields of different amplitudes and region 2 is irradiated by a linearly polarized laser field.
• Figure 2: The transmissions as a function of incident energy $\varepsilon$ for normal incident $\phi=0$, $\varpi=1$, $B_1=B_2=1$ and $d_1=d_2=L=1$. Three values of $\alpha$ (a): $\alpha=0.1$, (b): $\alpha =0.75$, (c): $\alpha=2$. Here $T$ (magenta line), $T_0$ (blue line), $T_1$ (red line), $T_{-1}$ (cyan line), $T_2$ (green line), and $T_{-2}$ (yellow line).
• Figure 3: The transmissions as a function of incident energy $\varepsilon$ for normal incident, $\varpi=1$, $\alpha=2$, $L=0.5$ and $d_1=d_2=1$. for three values of $B$ (a): $B=1$, (b): $B=3$, (c): $B=5$. Here $T$ (magenta line), $T_0$ (blue line), $T_1$ (red line), $T_{-1}$ (cyan line), $T_2$ (green line), and $T_{-2}$ (yellow line).
• Figure 4: (The transmissions as a function of the inter-barrier distance $L$ for normal incident, $d_1=d_2=1$, $\varepsilon=15$ and $\varpi=1$. Three values of $\alpha$ (a): $\alpha=1$, (b): $\alpha=1.5$, (c): $\alpha=2$. Here $T$ (magenta line), $T_0$ (blue line), $T_1$ (red line), $T_{-1}$ (cyan line), $T_2$ (green line), and $T_{-2}$ (yellow line).
• Figure 5: The transmissions as a function of the magnetic field ratio $B_2/B_1$ for normal incident, $\varepsilon=15$, $\varpi$=1 and $d_1=d_2=d=1$. Three values of $\alpha$ (a): $\alpha=1$, (b): $\alpha=1.5$, (c): $\alpha=2$. Here $T$ (magenta line), $T_0$ (blue line), $T_1$ (red line), $T_{-1}$ (cyan line), $T_2$ (green line), and $T_{-2}$ (yellow line).