Structured light and induced vorticity in superconductors I: Linearly polarized light

TL;DR

This work investigates imprinting and controlling topological excitations in a superconducting film using linearly polarized structured light. It employs the generalized time-dependent Ginzburg–Landau framework with a time-dependent vector potential from a Gaussian beam to show that vortex–antivortex pairs can be nucleated and driven while preserving zero net vorticity, presenting a quantum-printing viewpoint for transferring light's quantum numbers to the superconducting condensate. The results reveal regimes where long-lived or short-lived VP cycles occur depending on the EM frequency and flux amplitude, and they highlight the interplay between light-induced flux and gTDGL timescales. The study lays out experimental pathways using near-field THz illumination of ultra-thin Nb or similar superconductors and points toward optical control of SC topological states and future work on transferring spin and orbital angular momentum to superconducting matter.

Abstract

We propose an approach to use linearly polarized light to imprint superconducting vortices. Within the framework of the generalized time-dependent Ginzburg-Landau equations we demonstrate the induction of the coherent vortex pairs that are moving in phase with electormagnetic wave oscillations. The overall vorticity of the superconductor remain zero throughout the cycle. Our results uncover rich multiscale dynamics of SC vorticity and suggest new optical applications for various types of structured light. In departure from classical laser printing, the laser printing proposed here can be viewed as quantum print where we induce quantum excitations in the SC liquid.

Figures (10)

• Figure 1: Linearly polarized light-induced SC vorticity and time evolution of order parameter $|\psi|$. The snapshots of vorticity show the light induced vortex-antivortex pair (labeled $V_+$ and $V_-$), supercurrent (labeled $J_+$ with positive vorticity and $J_-$ with negative vorticity).
• Figure 2: (a) Schematic diagram of applied EM wave and SC thin film. (b) $A_{EM}$ and profile of the corresponding $(\nabla\times\boldsymbol{A_{EM}})_z$ at different time frames. (c) Flowchart of the gTDGL simulation.
• Figure 3: The SC state excited by the different sign of $B_z$. The sign of $B_z$ is tuned by add the phase $\phi_0$ into Eq. \ref{['eq:E_EM']}. (a) ($\phi_0=0$, first row) and (b) ($\phi_0=\pi$, second row) represent the magnetic flux from the same light source with 0 and $\pi$ phase shift, respectively. The profiles of $B_z/B_{c2}$ are shown on left side of gray arrows. The corresponding imprint distribution of the SC state show at right side of gray arrows, including $|\psi|$, $\theta_s$, $J/J_0$, and vorticity. The green dashed circles and inset axis at the left figures represent the beam spot and direction of coordinate. The notations $J_+$, $J_-$, $V_+$ and $V_-$ are consistent with those in Table \ref{['tab:symbol']}. Both (a) and (b) show 5 VPs in the snapshots.
• Figure 4: (a) The SC time evolution driven by light source with $\omega_{EM} = \omega_{GL}/40$. In the top row, the purple curve represents the normalized $E_0$ referenced the left axis, and gray curve is the out-of-plan flux $\Phi_B/\Phi_0$ referenced right axis. The second to fourth subplots show the vertical slice at middle of sample for $|\psi|$, $\theta_s/\pi$ and $\omega_{\nu,s}$. In the subplot of $|\psi|$, the left green dashed line marked $2w_0$ is the size of spot, and right dashed lines marked $\tau_1$ to $\tau_5$ represent selected moments corresponding to different stages of VP evolution, detailed in (b). In the $\omega_{\nu,s}$ subplot, the notations $J_+$, $J_-$, $V_+$ and $V_-$ are consistent with those in \ref{['tab:symbol']}. The dashed curves labeled G, S, R, H denotes the duration of the generation, quasi-steady state (dwell time of VP$_1$), recombination, healing processes, respectively. The black dashed lines cross all subplots at 40 and 80 $\tau_{GL}$ mark the interval of EM wave period. The complete dynamical results of $|\psi|$, $\theta_s$, $J$, and $\omega_{\nu,s}$ also demonstrate in the supplementary materials supp3. (b) Snapshot of $|\psi|$, $\theta_s$, $J$, and $\omega_{\nu,s}$ at different stages of the VP life time. (c) Schematic diagram of the cycling of free energy density.
• Figure 5: Similar simulations as \ref{['fig:osc_slow']} but with highter $\omega_{EM}$: (a) $\omega_{EM}=\omega_{GL}/10$ and (b) $\omega_{EM}=\omega_{GL}/2$. The red arrow insets in (b) indicate a VP life cycle, and the inset of $\abs{\psi}$ shows the profile of VPs at $4 \tau_{GL}$. The simulation condition of $E_{amp}$ in (a) is 4 times larger than the case of Fig. \ref{['fig:osc_slow']}, and in (b) is 60 times larger. The complete dynamical results of $|\psi|$, $\theta_s$, $J$, and $\omega_{\nu,s}$ also demonstrate in the supplementary materials supp4 and supp5.