Light-induced pseudo-magnetic fields in three-dimensional topological semimetals

TL;DR

This work demonstrates a Floquet-engineered route to generate and control axial gauge fields in three-dimensional Weyl semimetals via spatially modulated linearly polarized light, yielding a pseudo-magnetic field $\mathbf{B}_5$ through an effective axial potential $\mathbf{A}_5(\mathbf{r})$. Using a high-frequency expansion, the authors formulate how circular and linear polarizations shift or split Weyl nodes, with linear polarization enabling a controlled separation of same-chirality Weyl nodes at the R point. They connect the texture of $\mathbf{A}_5(\mathbf{r})$ to a near-uniform $\mathbf{B}_5$ and compare Landau-level spectra to those from real magnetic fields, predicting clear optical signatures in both linear and second-order responses, including LL-induced oscillations and CPGE features. The results show that optically generated pseudo-gauge fields are dynamically tunable, spatially precise, and reversible, enabling real-time manipulation of topological properties and providing feasible experimental probes via optical conductivity measurements.

Abstract

In this work, we show that suitably designed spatially varying linearly polarized light provides a versatile route to generate and control pseudo-magnetic fields in Weyl semimetals through Floquet engineering. Within a high-frequency expansion, we derive an effective axial gauge potential $\mathbf{A}_5(\mathbf{r})$ whose curl gives the pseudo-magnetic field $\mathbf{B}_5(\mathbf{r})$. By mapping the light profile to $\mathbf{A}_5(\mathbf{r})$, we establish design principles for pseudo-magnetic field textures that mimic strain-induced gauge fields while offering key advantages like dynamic control, full reversibility, spatial selectivity, and absence of material deformation. We compare the Landau-level spectra produced by uniform real and pseudo-magnetic fields and also analyze both their linear optical conductivity and the second-order dc responses. Our results enable real-time manipulation of pseudo-magnetic fields and predict clear experimental signatures for optically engineered gauge fields in topological semimetals.

Figures (13)

• Figure 1: (a) Lattice model unit cell and (b) static energies along a high-symmetry path in the Brillouin zone.
• Figure 2: (a) Exact quasienergies for a model driven with circularly polarized light along a high-symmetry path for $\gamma=1.1$, $\hbar\Omega/t=5$ (orange), compared with the static energies (blue). (b) Quasienergies near the R point as a function $k_x$, which shows that the node shifts but does not split.
• Figure 3: (a) Exact quasienergies for a model driven with linearly polarized light along a high-symmetry path for $\gamma=1.1$ (orange), compared with the static energies (blue). (b) Quasienergies near the R point as a function $k_x$, which shows splitting of the node.
• Figure 4: Polar plot of Weyl-node separation $(k_0^+-k_0^-)$ vs. polarization angle $\theta$ of light in y-z plane. We have used $\gamma=1.1$.
• Figure 5: Different spatial profiles for the vector potential $A(y)$ and the corresponding pseudo-magnetic fields for $\gamma=1.1$, $A_1=0.004/a$, $N_y=150$.