Quantum coherence tomography of light-controlled superconductivity

Abstract

The coupling between superconductors and oscillation cycles of light pulses, i.e., lightwave engineering, is an emerging control concept for superconducting quantum electronics. Although progress has been made towards terahertz-driven superconductivity and supercurrents, the interactions able to drive non-equilibrium pairing are still poorly understood, partially due to the lack of measurements of high-order correlation functions. In particular, the sensing of exotic collective modes that would uniquely characterize light-driven superconducting coherence, in a way analogous to the Meissner effect, is very challenging but much needed. Here we report the discovery of parametrically driven superconductivity by light-induced order-parameter collective oscillations in iron-based superconductors. The time-periodic relative phase dynamics between the coupled electron and hole bands drives the transition to a distinct parametric superconducting state out-of-equalibrium. This light-induced emergent coherence is characterized by a unique phase–amplitude collective mode with Floquet-like sidebands at twice the Higgs frequency. We measure non-perturbative, high-order correlations of this parametrically driven superconductivity by separating the terahertz-frequency multidimensional coherent spectra into pump–probe, Higgs mode and bi-Higgs frequency sideband peaks. We find that the higher-order bi-Higgs sidebands dominate above the critical field, which indicates the breakdown of susceptibility perturbative expansion in this parametric quantum matter.

Dynamical interplay between superconductivity and pseudogap in cuprates as revealed by terahertz third-harmonic generation spectroscopy

“…Differentiating between the Higgs and Cooper pair breaking contributions to THG signals is a challenging task. Recent studies have suggested that 2D terahertz spectroscopy, which involves varying both gating time and pump-probe delay time, is an efficient way for distinguishing between the two pathways (39,40).…”

Tracing the dynamics of superconducting order via transient terahertz third-harmonic generation

“…The direct comparison with TR-ARPES data ( 47 ), where similar suppression and recovering dynamics have been reported, provides a benchmark of the ability of 2D THG spectroscopy to directly access the pump-induced quench of the SC order. On a similar avenue, 2D THz experiments with broadband pulses ( 48 , 49 ) could serve as probes for the transient regime. 2D transient THG spectroscopy thus offers an additional tool to investigate the quenching and recovery of the Higgs and phase excitations of the SC condensate in unconventional superconductors and sheds light on the fundamental pairing mechanism at play in these systems.…”

Enhanced quantum resources via two distant atom-cavity systems under the influence of atomic dissipation

“…Quantum coherence is another key quantum resource that makes clear the boundary between the quantum and classical contexts. Some extensive quantum phenomena such as interference [25], laser [26], superconductivity [27] and superfluidity [28,29] may be interpreted based on quantum coherence. In fact, quantum coherence provides some profound merits for quantum metrology [30,31], quantum key distribution [32], entanglement creation [33,34].…”