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Applied Physics Letters

Helicity-controlled switching of superconducting states by radiation pulse

Mihail D Croitoru, Brahim Lounis, A. I. Buzdin

Published Sep 18, 2023• 9 citations
Publisher

Abstract

We provide a theoretical analysis of the possibility of using circularly polarized radiation to switch between two different quantum states of a superconducting nanoring subjected to the half quantum flux. Numerical modeling, performed in the framework of the time-dependent Ginzburg–Landau equation, reveals the condition for on-demand switching between current-carrying states with different helicities with 100% probability. An experimental demonstration of this effect will be unambiguous evidence of the inverse Faraday effect in superconductors and pave the way for the design of light-operated superconducting devices.

DOI
10.1063/5.0165874

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Publisher's Note: “Helicity-controlled switching of superconducting states by radiation pulse” [Appl. Phys. Lett. 123 , 122601 (2023)]

Mihail D Croitoru, Brahim Lounis, A. I. Buzdin

Applied Physics Letters•Oct 23, 2023•0 citations

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arXiv:2502.17980•ACS Nano•Aug 4, 2025•4 citations
We provide a theoretical analysis of the possibility of using circularly polarized radiation to switch between two different quantum states of a superconducting nanoring subjected to the half quantum flux. Numerical modeling, performed in the framework of the time-dependent Ginzburg–Landau equation, reveals the condition for on-demand switching between current-carrying states with different helicities with 100% probability. An experimental demonstration of this effect will be unambiguous evidence of the inverse Faraday effect in superconductors and pave the way for the design of light-operated superconducting devices.
Recently, the use of circularly polarized radiation for on-demand switching between distinct quantum states in a superconducting nanoring exposed to half-quantum magnetic flux has been proposed. However, the effectiveness of this method depends on the system's stability against local variations in the superconducting characteristics of the ring and flux fluctuations. In this study, we utilize numerical simulations based on the time-dependent Ginzburg-Landau equation to evaluate the influence of these inevitable factors on the switching behavior. The results obtained demonstrate that the switching phenomena remain remarkably robust, providing confidence in their experimental observation.
Abstract The ability to rapidly control and manipulate superconducting states is one of the great challenges of modern condensed matter physics. Circularly polarized radiation interacting with a superconducting condensate acts as an effective magnetic field that can generate supercurrents and DC magnetic moments through the inverse Faraday effect (IFE). Using the time‐dependent Ginzburg–Landau (TDGL) equation formalism, the current‐carrying states of a small superconducting ring illuminated by such radiation is calculated. Numerical simulations demonstrate the possibility to on‐demand switch between current‐carrying states in the superconductor by controlling the helicity of the electromagnetic field polarization. This result opens the way to all‐optical operation of superconducting devices.
The Cooper pairs in superconducting condensates are shown to acquire a temperature-dependent dc magnetic moment under the effect of the circularly polarized electromagnetic radiation. The mechanisms of this inverse Faraday effect are investigated within the simplest version of the phenomenological dynamic theory for superfluids, namely, the time-dependent Ginzburg-Landau (GL) model. The light-induced magnetic moment is shown to be strongly affected by the nondissipative oscillatory contribution to the superconducting order parameter dynamics, which appears due to the nonzero imaginary part of the GL relaxation time. The relevance of the latter quantity to the Hall effect in the superconducting state allows us to establish the connection between the direct and inverse Faraday phenomena.
Superconducting radiation sensors are of particular interest for imaging applications in the sub-mm wavelength band because of their extraordinary sensitivity. The rising number of sensors integrated in one array entails the requirement of multiplexing techniques in order to reduce the number of wires leading into the cryogenic stage and thus reduce the thermal losses. One kind of promising code division multiplexing technique is based on a current steering switch (CSS), which is composed of two identical superconducting quantum interference devices (SQUIDs) in parallel current paths. One of them is switched from the superconducting into the normal state controlled by the applied magnetic flux. In this way the signal path can be altered and they can act as a polarity switch for analogue signals. We pursue this concept to use rapid single flux quantum (RSFQ) electronics for controlling these switches. As a first step, the SQUIDs of the CSS are inductively coupled to the storing loops of two delay flip flops (DFFs). Thus, one is able to toggle the polarity of the analogue switch by controlling the state of the DFF by RSFQ control signals. The results of simulations and measurements and also margin analyses are discussed.
Superconducting circuits are promising candidates for future computational architectures; however, practical applications require fast operation. Here, we demonstrate fast, gate-based switching of an Al nanowire-based superconducting switch in time-domain experiments. We apply voltage pulses to the gate while monitoring the microwave transmission of the device. Utilizing the usual leakage-based operation, these measurements yield a fast, 1-2 ns switching time to the normal state, possibly limited by the bandwidth of our setup, and a 15-20 ns delay in the normal to superconducting transition. However, having a significant capacitance between the gate and the device allows for a different operation, where the displacement current, induced by the fast gate pulses, drives the transition. The switching from superconducting to the normal state yields a similar fast time scale, while in the opposite direction the switching is significantly faster (4-6 ns) than the leakage-based operation, which may be further improved by a better thermal design. The measured short time scales and the displacement current-based switching operation will be important for future fast and low-power-consumption applications.