Ultrafast spectroscopy is an emerging technique with great promise in the study of quantum materials, as it makes it possible to track similarities and correlations that are not evident near equilibrium. Thus far, however, the way in which these processes modify the electron self-energy-a fundamental quantity describing many-body interactions in a material-has been little discussed. Here we use time-and angle-resolved photoemission to directly measure the ultrafast response of self-energy to near-infrared photoexcitation in hightemperature cuprate superconductor. Below the critical temperature of the superconductor, ultrafast excitations trigger a synchronous decrease of electron self-energy and superconducting gap, culminating in a saturation in the weakening of electron-boson coupling when the superconducting gap is fully quenched. In contrast, electron-boson coupling is unresponsive to ultrafast excitations above the critical temperature of the superconductor and in the metallic state of a related material. These findings open a new pathway for studying transient self-energy and correlation effects in solids.

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The perovskite iridates Sr 2 IrO 4 and Sr 3 Ir 2 O 7 represent novel systems for exploring the electronic structure that is characteristic of Mott insulators upon carrier doping. Using angle-resolved photoemission spectroscopy (ARPES), we reveal a previously unobserved suppression of spectral weight near the Fermi level in the conduction band of very lightly electron-doped (Sr 1−x La x) 3 Ir 2 O 7 followed by a loss of coherence at high temperature. The doping and temperature dependence of this suppression suggests a correspondence with the antiferromagnetic Mott state. These results connect (Sr 1−x La x) 3 Ir 2 O 7 to other doped Mott insulators and add to the growing evidence of universal physics in these systems.