Unconventional spectral signature of Tc in a pure d-wave superconductor

In bulk BCS superconductors, the superconducting transition has four prominent signatures: the development of zero resistance, the onset of Meissner effect, the peak of the electronic specific heat coefficient, and the opening of the spectral gap. In the high-Tc cuprates, although the first three signatures are routinely observed, the gap is also found at temperatures above Tc and the spectral fingerprint of the phase transition remains unclear.

In this talk, I will present the missing piece of the puzzle revealed by high-precision photoemission spectroscopy [1, 2]. Focusing on overdoped Bi2212 above the pseudogap critical doping [3], we observe a pure d-wave gap that evolves smoothly across Tc free from the interference of competing orders. On the other hand, the “filling” rate of the gap is found to sharply peak at Tc and create the thermodynamic anomaly across the phase transition. I will discuss the implications of our results in the context of recent progress on overdoped cuprates.

[1] Chen, Hashimoto et al., Nature 601, 562 (2022)

[2] He, Chen, Li et al., PRX 11, 031068 (2021)

[3] Chen, Hashimoto et al., Science 366, 1099 (2019)