Tuning the electromagnetic local density of states in graphene-covered systems via strong coupling with graphene plasmons

It is known that the near-field spectrum of the local density of states of the electromagnetic field above a SiC-air interface displays an intense narrow peak due to the presence of a surface polariton. It has been recently shown that this surface wave can be strongly coupled with the sheet plasmon of graphene in graphene-SiC heterosystems. Here, we explore the interplay between these two phenomena and demonstrate that the spectrum of the electromagnetic local density of states in these systems presents two peaks whose positions depend dramatically both on the distance to the interface and on the chemical potential of graphene. This paves the way toward active control of the local density of states.

Figure 1

Scheme of the system. A dielectric (SiC) substrate is covered with a monolayer graphene sheet coinciding with the plane $z=0$.

Figure 2

EM-LDOS at a distance of $d=50$nm from (a) a SiC substrate, (b) a suspended graphene sheet, and (c) a graphene-covered SiC substrate. In panel (a) the total EM-LDOS (solid line) is decomposed in its electric (dot-dashed line) and magnetic (dotted line) contributions. In panels (b) and (c), corresponding to suspended graphene and graphene-covered SiC, respectively, only the total EM-LDOS is represented, for three values of the graphene chemical potential: $\mu =0$eV (blue dot-dashed line), $\mu =0.2$eV (red dashed line), and $\mu =0.5$eV (black solid line).

Figure 3

Dispersion relations of surface modes for SiC (black dashed line), suspended graphene (green dotted line), and graphene-covered SiC (red solid line). The blue dot-dashed line represents the light cone in vacuum. The comparison is made for three different values of the graphene chemical potential, $\mu =\left(\mathrm{a}\right)0,\left(\mathrm{b}\right)0.2,\mathrm{and}\left(\mathrm{c}\right)0.5$eV.

Figure 4

EM-LDOS for a SiC-graphene sample ($\mu =0.5$eV) for different values of the sample-tip distance $d$. The orange dot-dashed vertical line corresponds to $\omega ={\omega }_T$, whereas the dashed black vertical line is $\omega ={\omega }_{\mathrm{spp}}$.