Petahertz non-linear current in a centrosymmetric organic superconductor

Abstract

Charge acceleration during an intense light field application to solids attracts much attention as elementary processes in high-harmonic generation and photoelectron emission. For manipulating such attosecond dynamics of charge, carrier-envelope-phase (CEP: relative phase between carrier oscillation of light field and its envelope function) control has been employed in insulators, nanometal and graphene. In superconducting materials, collective control of charge motion is expected because of its strongly coherent nature of quasiparticles. Here we report that, in a layered organic superconductor, a non-linear petahertz current driven by a single-cycle 6 femtosecond near infrared field shows up as second harmonic generation (SHG), which is in contrast to the common belief that even harmonics are forbidden in the centrosymmetric system. The SHG represents a CEP sensitive nature and an enhancement near the superconducting temperature. The result and its quantum manybody analysis indicate that a polarized current is induced by non-linear acceleration of charge, which is amplified by superconducting fluctuations. This will lead to petahertz functions of superconductors and of strongly correlated systems.

Multiferroic/Polymer Flexible Structures Obtained by Atomic Layer Deposition

“…In a centrosymmetric organic superconductor, there is a polarized current induced by a nonlinear charge acceleration, which is amplified by charge fluctuations. This can lead to the generation of higher harmonics and photoelectron emission [ 12 ]. However, the magnetic properties of the material were not investigated in this work.…”

Photoinduced Pseudospin Polarization in a Three-Orbital Hubbard Model

“…15,16) On a timescale shorter than the electron-electron scattering time, inversion symmetry can be broken to cause second harmonic generation in centrosymmetric systems. [17][18][19][20] As to changes in the time-reversal symmetry, there are photoinduced phase transitions between the ferromagnetic metal and the antiferromagnetic insulator in perovskite manganites, 9,13,14) which are often treated in the double exchange model. These transitions are believed to be achieved by domain growth from the seeds of fluctuations.…”

Mechanism for Synchronization of Charge Oscillations in Dimer Lattices

“…[32][33][34][35][36][37][38][39][40] Recently, second harmonic generation has been observed in a centrosymmetric organic superconductor κ-(bis[ethylenedithio]tetrathiafulvalene) 2 Cu[N(CN) 2 ]Br [κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Br] through a nonlinear petahertz current before substantial scattering processes occur. 41) In this compound, [42][43][44][45][46][47][48][49][50][51] which is known to have a dimer lattice, stimulated emission is observed after strong photoexcitation. 52) This stimulated emission is also caused by a nonlinear charge oscillation -an electronic breathing mode -as has been shown by numerical calculations based on the exact diagonalization method.…”