Active magneto-optical control of spontaneous emission in graphene

We investigate the spontaneous emission rate of a two-level quantum emitter near a graphene-coated substrate under the influence of an external magnetic field or strain induced pseudomagnetic field. We demonstrate that the application of the magnetic field can substantially increase or decrease the decay rate. We show that a suppression as large as $99\%$ in the Purcell factor is achieved even for moderate magnetic fields. The emitter's lifetime is a discontinuous function of $\left|\mathbf{B}\right|$, which is a direct consequence of the occurrence of discrete Landau levels in graphene. We demonstrate that, in the near-field regime, the magnetic field enables an unprecedented control of the decay pathways into which the photon/polariton can be emitted. Our findings strongly suggest that a magnetic field could act as an efficient agent for on-demand, active control of light-matter interactions in graphene at the quantum level.

Figure 1

Quantum emitter at a distance $d$ above a graphene sheet on the top of a substrate of permittivity ${\varepsilon }_s\left(\omega \right)$. The whole system is under the influence of a magnetic field $\mathbf{B}=B\widehat{\mathbf{z}}$.

Figure 2

Normalized decay rate ${\mathrm{\Gamma }}_{\perp }/{\mathrm{\Gamma }}_0$ as a function of distance $d$ between the emitter and the graphene-SiC half space for different magnetic fields. The inset presents the relative SE rate $\mathrm{\Delta }{\mathrm{\Gamma }}_{\perp }$ as a function of $d$ for the same values of $B$.

Figure 3

The decay channel probabilities as a function of (a) $d$ and (b) $B$ for ${\mu }_c=115$ meV. In (a) solid and dotted curves are for $B=5$ T and $B=15$ T, respectively. In (b) the distance is fixed at $d=4\mu \mathrm{m}$. ${\mathrm{\Gamma }}_{\perp }(d,B)/{\mathrm{\Gamma }}_0$ as a function of $B$ is plotted in (c) $d=200$ nm and (d) $d=1\mu \mathrm{m}$. The vertical lines show the position of the peak of ${\mathrm{\Gamma }}_{\perp }(d,B)/{\mathrm{\Gamma }}_0$ obtained via Eq. (11).

Figure 4

Three-dimensional plot of the relative SE $\mathrm{\Delta }{\mathrm{\Gamma }}_{\left|\right|}({\mu }_c,B)$ as a function of both ${\mu }_c$ and $B$ for $d=2\mu \mathrm{m}$.

Figure 5

Integrands of Eqs. (D10) and (D11) for the quantum emitter's dissipated power by nonradiative processes. On the left we plot the the integrand of Eq. (D10); on the right we plot the integrand of (D11), splitting it into the individual contributions from the absorption coefficients ${\mathcal{A}}_{\mathrm{p}}$ and ${\mathcal{A}}_{\mathrm{s}}$. The vertical dashed lines mark the points $k=k_0$ and $k=k_0\sqrt{{\varepsilon }_s/{\varepsilon }_0}$. The values of $B=5$ T and ${\mu }_c=115$ meV were used.