Nonlinear charge oscillation driven by a single-cycle light field in an organic superconductor

Abstract

Intense light-field application to solids produces enormous/ultrafast non-linear phenomena such as high-harmonic generations 1, 2 and attosecond charge dynamics 3, 4 . They are distinct from conventional photonics. However, main targets have been limited to insulators and semiconductors, although theoretical approaches have been made also for correlated metals and superconductors 5 . Here, in a layered organic superconductor, a non-linear charge oscillation driven by a nearly single-cycle strong electric field of >10 megavolts /cm is observed as a stimulated emission. The charge oscillation is different from a linear response and ascribed to a polar charge oscillation with a period of 6 fs. This non-linear polar charge oscillation is enhanced by critical fluctuations near a superconducting transition temperature and a critical end point of first order Mott transitions. Its observation on an ultrafast timescale of 10 fs clarifies that the Coulomb repulsion plays an essential role in superconductivity of organic superconductors. Supplementary information forNonlinear charge oscillation driven by a single-cycle light field in an organic superconductor

High-order nonlinear optical response of a twisted bilayer graphene

“…This phenomenon has attracted interest not only for compact frequency converter applications [12,13] but also as a probe of electron dynamics in intense optical fields [14]. Among various systems such as semiconductors [15][16][17][18][19][20][21][22][23][24][25], superconductors [26][27][28], strongly correlated systems [29][30][31][32][33][34], quantum magnets [35][36][37], and topological insulators [38,39], Dirac materials have turned out to have extremely large nonlinear susceptibility from the mid-infrared [40][41][42] down to the teraherz [43][44][45] frequency regimes. In particular, nonlinear response of graphene has been studied extensively [46][47][48][49][50].…”

Petahertz non-linear current in a centrosymmetric organic superconductor

“…A broadband infrared spectrum covering 1.2-2.3 μm of the 6 fs pulse is obtained by focusing a carrier-envelope phase (CEP) stabilized idler pulse (1.7 μm) from an optical parametric amplifier (Quantronix HE-TOPAS pumped by Spectra-Physics Spitfire-Ace) onto a hollow fiber set within a Kr-filled chamber (Femtolasers). Pulse compression is performed using both active mirror (OKO, 19-ch linear MMDM) and chirped mirror (Femtolasers and Sigma-Koki) techniques 29,34 .…”

“…The possibility of symmetry breaking induced by photo-carrier generation near the surface is also excluded by the fact that the lifetime of carriers (ca. 500 fs) 29 (Supplementary note 3) is much longer than the time scale of the non-linear effect which drives the SHG (ca. 40 fs is evaluated from the bandwidth as discussed later).…”

“…In superconductors, optical responses have been discussed in terms of non-equilibrium quasi-particle dynamics on the time scale of picosecond 22 – 25 , coherent excitation of the Higgs mode 26 and light-induced superconductivity 27 , 28 . On the other hand, petahertz light functions, driven by the non-linear current during a light pulse is also expected to be characteristic, reflecting the ultrafast time scale of superconducting fluctuations in κ-(BEDT–TTF) 2 Cu[N(CN) 2 ]Br 29 .…”

Multi-component Time-dependent Ginzburg–Landau Study of Photo-excitation Effects on Superconducting Fluctuation

“…The photo-excitations on the solid-state materials can induce interesting phenomena which cannot be realized in the equilibrium state [1][2][3][4][5]. Specifically for superconductors the recent experiments have opened a new possibility to stabilize the superconductivity even above the transition temperature [1,3,4].…”