One of the first physical quantities calculated by Bardeen, Cooper, and Schrieffer, in establishing the microscopic theory for conventional superconductors (in 1957 at UIUC), is the specific heat jump at the transition temperature Tc. In the high-Tc cuprates, the specific heat anomaly across the superconducting transition is less well understood, despite being observed some 30 years ago. In the first part of this talk, I will present our effort in understanding this transition and its thermodynamic signature, using high-precision ARPES measurements on the prototypical cuprate Bi2212 [1].
In the second part, I will focus on a separate topic, a collective mode in multiband metals associated with distinct electron motion, or “demon”, predicted by Pines in 1956 and recently observed at UIUC in the 3-dimensional bulk material Sr2RuO4 [2]. I will present a spatial-temporal imaging experiment from Berkeley that showcases the existence of such a mode in the 2-dimensional graphene [3].
[1] S. D. Chen, M. Hashimoto et al., Nature 601, 562 (2022)
[2] Husain et al., arXiv:2007.06670 (2022), Nature 621, 66 (2023)
[3] W. Zhao, S. Wang et al., Nature 614, 688 (2023)
