In-situ creation and control of Josephson junctions with a laser beam

Abstract

We propose the use of a laser beam tightly focused on a superconducting strip to create a Josephson junction by photothermal effect. The critical current of this junction can be easily controlled by the laser intensity. We show that a periodic modulation of the intensity substantially changes the dynamic properties of the junction and results in the appearance of Shapiro steps without microwave radiation. The experimental realization of optically driven Josephson junctions may open a way for the ultra-fast creation and switching of complex patterns of superconducting devices with tunable geometry and current-phase relations.A Josephson junction (JJ), consisting of two superconductors separated by a nonsuperconducting material (the so-called weak link) or a solid superconductor with an artificial constriction, is one of the key elements of modern cryogenic electronics, 1 quantum computing systems, 2,3 ultrasensitive electric and magnetic sensors 4 and other types of quantum devices. The non-dissipative electric current flowing through the junction is coupled with the phase difference between the gap potentials inside the superconducting electrodes, and the corresponding current-phase relation (CPR) ( ) determines all main static and dynamic characteristics of a Josephson system. 5,6 For basic JJs with an insulating or a normal metal weak link, the CPR is primary controlled by temperature and/or external magnetic field. Cooling the sample switches the CPR from a sinusoidal function to a linear one, while the magnetic field damps the critical current (the maximal current which can flow through the junction without dissipation) and induces peculiar Fraunhofer oscillations. 5 Even richer physics arise when the superconducting electrodes are separated by a ferromagnetic layer. 7 In contrast to the usual JJ with the zero phase in the ground state, ferromagnets allow to create -junctions with a spontaneous ground state phase = 8,9 or even 0 -junctions with = 0 ≠ 0, . The latter possibility requires a strong spin-orbit coupling 10,11 or a large spin splitting of the electron energy bands due to the exchange field. 12,13 By applying an external magnetic field and changing the exchange field orientation, one can tune 0 , which opens new perspectives for the elements of the rapid single flux-quantum logics. 1,14,15 However, in all existing types of tunable JJs, the weak link needs to be embedded into the system during the fabrication process and can hardly be tuned afterwards. The versatility and performance of Josephson devices would greatly benefit from simple methods to tune in situ the CPR of the built-in JJs and eliminate fabrication inhomogeneities.

Creation of superconducting vortices by angular momentum of light

“…20,21 The time dependent Ginzburg-Landau (TDGL) equation is given by −Γ ∂ψ ∂t = δF δψ * . 28 With the proper normalization 12 , it reduces to…”

“…Interaction of light with condensed matter systems has offered a new approach to control and study them in an ultrafast manner. [1][2][3][4] Various aspects of superconductors under light illumination have been investigated such as response of an Abrikosov vortex 5 , superconducting single photon detectors 6,7 , excitation of Higgs modes [8][9][10][11] , laser created Josephson junctions 12 , manipulation of a vortex 13 , probe and control of chirality of Cooper pairs [14][15][16] , and excitation of phonons 18,19 , which are fundamentally and technologically important. Most of the previou works have considered energy transfer of light.…”

Optical vortex induced spatio-temporally modulated superconductivity in a high-Tc cuprate

“…In the field of photoinduced phase transition spectroscopy, theoretical proposals for optical excitation of electric currents 10 , magnetic defects 11,12 , and superconducting (SC) vortices 13,14 , which take advantage of the characteristics of structured light waves, have attracted particular attention. Spatially modulated photoinduced phase transitions are also expected to be applied to ultrafast devices with complex patterns using highly controllable beam-shaping techniques 15,16 . However, their experimental realizations have been, thus far, limited mainly because of the spatial mismatch between the electron system and the optical field 17,18 .…”

Optical vortex induced spatio-temporally modulated superconductivity in a high-Tc cuprate

“…In the field of solid-state spectroscopy, theoretical proposals for optical excitation of electric currents 13 , magnetic defects 14,15 , and superconducting vortices 16,17 , which take advantage of the characteristics of structured light waves, have attracted particular attention. Spatially modulated photoinduced phase transitions are also expected to be applied to ultrafast devices with complex patterns using highly controllable beam-shaping techniques 18,19 . However, their experimental realizations have been, thus far, limited mainly because of the spatial mismatch between the electron system and the optical field.…”