Abstract
Illumination of light on matter normally causes heating and destroys the ordered ground states. Despite this common understanding, recent advances in ultrafast light sources have enabled the non-thermal control of quantum phases. Here, we report the light-induced enhancement of superconductivity in a thin film of an iron chalcogenide FeSe0.5Te0.5, which exhibits multiple quantum condensates associated with the multi-orbital character. Upon the photoexcitation, we observed a transient increase of the superfluid density as indicated by the optical conductivity in the frequency range of superconducting gaps. The light-induced enhancement of superconductivity is further corroborated by the photoinduced enhancement of terahertz third harmonic generation, which is accounted for by the Higgs mode response. The ultrafast dynamics of two superfluid components revealed by frequency- and time-resolved terahertz measurements indicate the interplay between the condensates through the interband Cooper pairings while suggesting the potential tunability of the pairing interaction by light in the ultrafast timescale.
Highlights
Illumination of light on matter normally causes heating and destroys the ordered ground states
Tc reaches even 65 K in a monolayer FeSe grown on SrTiO3 substrate as estimated from the gap closing temperature in angle-resolved photoemission spectroscopy (ARPES)[10,11,12]
Tc = 16 K defined by the zero resistivity (Fig. 1e), a missing of the spectral weight is observed in the real-part optical conductivity (σ1) in the range of 1–10 meV, indicating the opening of the superconducting gap with the gap size of ~ 10 meV
Summary
Illumination of light on matter normally causes heating and destroys the ordered ground states. The Fermi energies for both electron and hole bands are shown to be exceptionally small and comparable to the superconducting gaps, and notably, a clear correlation between Tc and the Fermi surface topology has been revealed from the ARPES study with tuning the chemical potential by the surface dosing[17]. Different from these static tunings, one can consider the dynamical tuning by strong photoexcitation as an alternative route to control the superconductivity and other competing or coexisting orders. The enhancement of the superconducting order parameter is further corroborated by the THz-third-harmonic generation (THG) signal, which is accounted for by the Higgs mode response
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