Evidence for hidden fermion that triggers high-temperature superconductivity in cuprates

TL;DR

This paper uncovers hidden fermions in cuprate high-temperature superconductors, revealing their role in forming strongly bound Cooper pairs and linking the pseudogap phase to superconductivity, which explains the high Tc.

Contribution

It demonstrates that hidden fermions arising from strong electron correlations are key to high Tc in cuprates, a mechanism distinct from conventional bosonic-mediated pairing.

Findings

Hidden fermions emerge from strong electron correlations.

Hidden fermions persist above Tc and relate to the pseudogap phase.

The mechanism explains the high binding energy of Cooper pairs in cuprates.

Abstract

In superconductors, electrons bound into Cooper pairs conduct a dissipationless current. The strength of the Cooper pairs scales with the value of the critical transition temperature (Tc). In cuprate high-Tc superconductors, however, the pairing mechanism is still unexplained. Here we unveil why in the cuprates the Cooper pairs are so strongly bound to work out the extraordinary high Tc. From one-to-one correspondence between numerical simulation on a microscopic cuprate model and a simple two-component fermion model, we show that hidden fermions emerge from the strong electron correlation and give birth to the strongly bound Cooper pairs. This mechanism is distinct from a conventional pairing mediated by some bosonic glue, such as phonons in conventional superconductors. The hidden fermions survive even above Tc and generate the strange-metal pseudogap phase. This reveals an unprecedented direct relationship between the pseudogap phase and superconductivity in the cuprates.