Tunable point nodes from line-node semimetals via application of light

We propose that illumination with light provides a useful platform for creating tunable semimetals. We show that by shining light on semimetals with a line degeneracy, one can convert them to a point-node semimetal. These point nodes are adjustable, and their position can be controlled by simply rotating the incident light beam. We also discuss the implications of this change in Fermi-surface topology as manifested in transport observables.

Figure 1

Energy eigenvalues for the low-energy model with $k_z=0$ for (a) $\mathrm{\Delta }\epsilon =0.2$ and (b) $\mathrm{\Delta }\epsilon =-0.2$, in the absence of light. Note the line-node degeneracy in the latter case and a band insulator in the former. (c) Photon-dressed energy eigenvalues with $\mathrm{\Delta }\epsilon =-0.2,{\mathcal{A}}_y={\mathcal{A}}_z=0.5$ for a circularly polarized beam. The line degeneracy between the two bands is reduced to two points located symmetrically along $k_y=0$. Here and henceforth, we have set ${\epsilon }_0=0,a_{xy}=0,a_z=1.0,v=1.0,b_{xy}=1.0,b_z=1.0$, and $\omega =1.0$.

Figure 2

Pseudospin texture of the lower [(a) and (c)] and upper [(b) and (d)] bands with opposite polarizations of the incident beam with $\eta =+1$ [(a) and (b)] and $\eta =-1$ [(c) and (d)]. The texture reverses as the handedness of the beam is reversed.

Figure 3

Densities of states in the $k_x\text{−}{k}_y$ plane at the energy of the nodal line ($E=0$) for (a) ${\mathcal{A}}_y={\mathcal{A}}_z=0$, (b) ${\mathcal{A}}_y={\mathcal{A}}_z=0.25$, and (c) ${\mathcal{A}}_y={\mathcal{A}}_z=0.5$. The same quantity plotted at an energy above the nodal line ($E=0.1$) for (d) ${\mathcal{A}}_y={\mathcal{A}}_z=0$, (e) ${\mathcal{A}}_y={\mathcal{A}}_z=0.25$, and (f) ${\mathcal{A}}_y={\mathcal{A}}_z=0.5$. A broadening of $\delta =0.001$ has been used for these plots.

Figure 4

Position of the point node as a function of varying angle of the incident laser beam. The position can be continuously tuned as the beam is rotated.

Figure 5

Sharvin conductance as a function of Fermi energy for (a) ${\mathcal{A}}_y={\mathcal{A}}_z=0$ and (b) ${\mathcal{A}}_y={\mathcal{A}}_z=0.5$. The scaling dependence on energy changes on applying light.