Low Temperature Physics: 48, 371 (2022); https://doi.org/10.1063/10.0010200
On the theory of nonhomogeneous nonequilibrium superconductivity in 2D systems with massless fermions
V. M. Loktev
Bogolyubov Institute of Theoretical Physics of the National Academy of Sciences of Ukraine, Kiev 03143, Ukraine
Department of Physics, University of Central Florida, Orlando, FL 32816, USA
Received December 28, 2021, published online March 25, 2022
We analyze static and nonequilibrium superconducting properties of a 2D relativistic-like model system with local electron-electron interaction, Rashba spin-orbit interaction αR in presence of time-dependent in-plane magnetic field H(t). It is shown that similarly to the 2D case with ordinary massive quasiparticle dispersion ε(k)~|k|2 at large fields such a system demonstrates a nonhomogeneous superconducting stripe phase with the order parameter Δ(r)=Δ(0)cos(2[μBB×r]n/ħυF) (B is the magnetic induction, υF is the Fermi velocity, n is the normal to the plane, μB is the Bohr magneton, and it is supposed that αR≪υF), where the stripes are oriented along the B direction. In the considered system the inter-stripe period L and the magnitude of the magnetic field B are related by a universal relation BL = ħυF/μB≃0.714•10-4 T•m. Contrary to the case of massive quasiparticles, where the condition αR~υF can be, in principle, satisfied by increasing αR or by charge doping (Fermi velocity decreasing), in a relativistic-like system, where υF is doping-independent and one-two orders of magnitude larger than typical Fermi velocity in the "standard" 2D systems, the stripe phase can be the ground state at a rather low doping level. We also analyzed the nonequilibrium properties of the system with a focus on the melting of the stripe order (when the magnetic field is quenched to a lower value) and stripe dynamics (when the field is rotated by 90° degrees) and found several notable results. In particular, it was shown that the stripe domains melt according to law R~1/√ ̅t at initial times, while at longer times they shrink exponentially. In the case of the flipped magnetic field, the stripe orientation gradually turns from x- to y-direction, and the intermediate "crossed-stripe" phase takes place during times of order of picoseconds. Such a crossed phase is built of periodic superconducting bubbles, that potentially may have applications in modern ultrafast superconducting technologies.
Key words: stripe superconductivity, nonequilibrium effects, superconducting nanodomains.