Light-induced Asymmetric Pseudogap below T$_\text{c}$ in cuprates

TL;DR

This study uses time- and angle-resolved photoemission to show that in cuprates, the pseudogap and superconductivity compete, with the pseudogap becoming asymmetric below T_c and being suppressed when superconductivity is restored.

Contribution

It provides direct experimental evidence that the pseudogap and superconducting states compete in cuprates, challenging the idea that superconductivity emerges from the pseudogap phase.

Findings

Pseudogap becomes asymmetric under high fluence excitation.

Superconductivity suppression correlates with pseudogap asymmetry.

Pseudogap and superconductivity coexist at intermediate states.

Abstract

To this day, high-temperature cuprate superconductors remain an unparalleled platform for studying the competition and coexistence of emergent, static and dynamic, quantum phases of matter exhibiting high transition temperature non-s-wave superconductivity, non-Fermi liquid transport and a still enigmatic pseudogap regime. However, how superconductivity emerges alongside and competes with the pseudogap regime remains an open question. Here, we present a high-resolution, time- and angle-resolved photoemission study of the near-antinodal region of optimally-doped Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$. For a sufficiently high excitation fluence, we disrupt superconductivity and drive a transient change from a symmetric superconducting-like to an asymmetric pseudogap-like density of states, for electronic temperatures well below the equilibrium superconducting critical temperature. Conversely, when the superconductivity is fully restored, the pseudogap is suppressed, as signaled by a fully particle-hole symmetric density of states. A unique aspect of our experiments is that the pseudogap coexists with superconducting features at intermediate times or at intermediate fluence. Our findings challenge the paradigm that superconductivity emerges by establishing phase coherence in the pseudogap. Instead, our experimental results, supported by phenomenological theory, demonstrate that the two states compete, and that the low-temperature ground state of the cuprates originates from a competition between superconducting and pseudogap states.