Stimulated emission of Cooper pairs in a high-temperature cuprate superconductor

Abstract

The concept of stimulated emission of bosons has played an important role in modern science and technology, and constitutes the working principle for lasers. In a stimulated emission process, an incoming photon enhances the probability that an excited atomic state will transition to a lower energy state and generate a second photon of the same energy. It is expected, but not experimentally shown, that stimulated emission contributes significantly to the zero resistance current in a superconductor by enhancing the probability that scattered Cooper pairs will return to the macroscopically occupied condensate instead of entering any other state. Here, we use time- and angle-resolved photoemission spectroscopy to study the initial rise of the non-equilibrium quasiparticle population in a Bi${}_2$Sr${}_2$CaCu${}_2$O${}_{8+\delta }$ cuprate superconductor induced by an ultrashort laser pulse. Our finding reveals significantly slower buildup of quasiparticles in the superconducting state than in the normal state. The slower buildup only occurs when the pump pulse is too weak to deplete the superconducting condensate, and for cuts inside the Fermi arc region. We propose this is a manifestation of stimulated recombination of broken Cooper pairs, and signals an important momentum space dichotomy in the formation of Cooper pairs inside and outside the Fermi arc region.

arXiv comment16 pages, 4 figures

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Cited by in corpus (5)

• Time- and Angle-Resolved Photoemission Studies of Quantum Materials
• Ultrafast Angle-Resolved Photoemission Spectroscopy of Quantum Materials
• Collapse of superconductivity in cuprates via ultrafast quenching of phase coherence
• Time-resolved ARPES on cuprates: Tracking the low-energy electrodynamics in the time domain
• Experimental realisation of tunable ferroelectric/superconductor (BTO/YBCO)N/STO 1D photonic crystals in the whole visible spectrum