Terahertz Second-Harmonic Generation from Lightwave Acceleration of Symmetry-Breaking Nonlinear Supercurrents

Vaswani, Chirag; Mootz, M.; Sundahl, C.; Mudiyanselage, D. H.; Kang, Jong Hon; Yang, Xu; Cheng, Di; Huang, Chih‐Ting; Kim, Richard H. J.; Liu, Zhaoyu; Luo, Liang; Perakis, I. E.; Eom, Chang‐Beom; Wang, J.

doi:10.1103/physrevlett.124.207003

Cited by 74 publications

(72 citation statements)

References 39 publications

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“…40 fs is an issue very different from the HHG driven by terahertz and mid-infrared fields, where the electric field continues to be applied even after a substantial number of scatterings occur. This is a very important perspective for petahertz functions and attosecond science of superconductors and of strongly correlated systems in addition to already realized terahertz functions of them 15,16,26,27 . In summary, this article demonstrates SHG in the centrosymmetric organic superconductor κ-(BEDT-TTF) 2 Cu[N (CN) 2 ]Br.…”

Section: Discussionmentioning

confidence: 95%

Petahertz non-linear current in a centrosymmetric organic superconductor

et al. 2020

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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.

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Section: Discussionmentioning

confidence: 95%

Petahertz non-linear current in a centrosymmetric organic superconductor

et al. 2020

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“…In addition, harmonic radiation was expected to be induced by broken inversion symmetry of the medium when the pump and probe waves were coincident. Presence of a quasi-static MER field removes isotropy of the sample in the interaction volume, thereby enabling second harmonic generation 20 , 21 . Thus second harmonic generation from the probe should be induced only during the M-E interaction caused by the pump pulse, producing a transient signal that lasts only as long as the induced rectification field.…”

Section: Resultsmentioning

confidence: 99%

Observation of magneto-electric rectification at non-relativistic intensities

et al. 2020

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The subject of electromagnetism has often been called electrodynamics to emphasize the dominance of the electric field in dynamic light–matter interactions that take place under non-relativistic conditions. Here we show experimentally that the often neglected optical magnetic field can nevertheless play an important role in a class of optical nonlinearities driven by both the electric and magnetic components of light at modest (non-relativistic) intensities. We specifically report the observation of magneto-electric rectification, a previously unexplored nonlinearity at the molecular level which has important potential for energy conversion, ultrafast switching, nano-photonics, and nonlinear optics. Our experiments were carried out in nanocrystalline pentacene thin films possessing spatial inversion symmetry that prohibited second-order, all-electric nonlinearities but allowed magneto-electric rectification.

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“…However, THz lightwave acceleration [25][26][27][28] of the condensate during cycles of carrier wave oscillations and electromagnetic propagation effects has been mostly neglected. Recent experimental observations of high-harmonic generation (HHG) at equilibriumsymmetry-forbidden frequencies together with long-lived gapless quantum states [1,2,17] confirmed the importance of Cooper pair center-of-mass momentum. However, such quantum transport effects during THz subcycle timescales [1,2,[25][26][27][28] require an extension of Anderson pseudospin precession models [41,[45][46][47][48].…”

Section: Introductionmentioning

confidence: 98%

“…Recent works have shown that ultrafast phase-coherent THz nonlinear spectroscopy [1][2][3][4][5] is a powerful tool for sensing and controlling nonequilibrium phases [6][7][8][9][10][11][12][13][14][15][16][17] and collective modes [18][19][20][21][22] of quantum materials. For example, the nonequilibrium dynamics of quasiparticles (QPs) in SCs has been characterized and controlled by THz pulses [23,24].…”

Section: Introductionmentioning

confidence: 99%

“…THz quantum quench of the SC order parameter by a singlecycle pulse yields access to a long-lived (tens of ns) gapless quantum fluid phase of QPs hidden by superconductivity [17]. By tuning multicycle THz pulses, the above QP state changes into a nonequilibrium gapless SC, i.e., a moving condensate with a gapless excitation spectrum, nearly unchanged macroscopic coherence, and infinite conductivity [1,2]. In all the above cases, the dynamics over hundreds of ps is controlled by lightwave few-cycle fields that last for only a few ps.…”

Section: Introductionmentioning

confidence: 99%

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Lightwave terahertz quantum manipulation of nonequilibrium superconductor phases and their collective modes

2020

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We present a gauge-invariant density matrix description of nonequilibrium superconductor (SC) states with spatial and temporal correlations driven by intense terahertz (THz) lightwaves. We derive superconductor Bloch-Maxwell equations of motion that extend Anderson pseudospin models to include the Cooper pair center-of-mass motion and electromagnetic propagation effects. We thus describe quantum control of dynamical phases, collective modes, quasiparticle coherence, and high nonlinearities during cycles of carrier wave oscillations, which relates to our recent experiments. Coherent photogeneration of a nonlinear supercurrent with a dc component, achieved via condensate acceleration by an effective lightwave field, dynamically breaks the equilibrium inversion symmetry. Experimental signatures include high harmonic light emission at equilibrium-symmetry-forbidden frequencies, Rabi-Higgs collective modes and quasiparticle coherence, and nonequilibrium moving condensate states tuned by few-cycle THz fields. We use such lightwaves as an oscillating accelerating force that drives strong nonlinearities and anisotropic quasiparticle populations to control and amplify different classes of collective modes, e.g., damped oscillations, persistent oscillations, and overdamped dynamics via Rabi flopping. Recent phase-coherent nonlinear spectroscopy experiments can be modeled by solving the full nonlinear quantum dynamics including self-consistent light-matter coupling.

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Terahertz Second-Harmonic Generation from Lightwave Acceleration of Symmetry-Breaking Nonlinear Supercurrents

Cited by 74 publications

References 39 publications

Petahertz non-linear current in a centrosymmetric organic superconductor

Petahertz non-linear current in a centrosymmetric organic superconductor

Observation of magneto-electric rectification at non-relativistic intensities

Lightwave terahertz quantum manipulation of nonequilibrium superconductor phases and their collective modes

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