PhD Princeton University (1985)
Condensed Matter Theory
Research interests include properties of heavy fermion and, more recently, high temperature cuprate and Fe-based superconductors. The cuprate materials, with Tc’s of order 100K or above, evolve by doping or applied pressure from 2D “parent” Mott insulators. The more recently discovered Fe-based pnictide and chalcogenide superconductors have Tc’s up to 55K and parent compounds are metallic. The physics of these new materials depends sensitively on the mulitorbital and multiband character of the Fermi surface. In the cuprates, there is strong evidence that superconductivity is unconventional (in particular, d-wave) in the sense that the superconducting order parameter or pair wave function has symmetry less than the underlying crystal lattice. While the order parameters in the Fe-pnictide systems are thought to be “s-wave” or “conventional” according to the above definition, they may change sign and/or have strong anisotropy and even gap nodes. Currently my research is focused on understanding the effects of the multiorbital physics on the pairing in both cuprates and pnictides, and exploring the consequences of this gap symmetry/structure phenomenologically. I have a continuing strong interest in the effects of disorder on the superconducting state and its competition with other ordered phases.
“Iron pnictides and chalcogenides: a new paradigm for superconductivity” A. Coldea, H. Ding, R. Fernandes, I. Fisher, P.J. Hirschfeld, and G. Kotliar, Nature 601, 35 (2022).
“Atomic-scale electronic structure of the cuprate pair density wave state coexisting with superconductivity,” P. Choubey, S. Joo, K. Fujita, Z. Du, S. D. Edkins, M.H. Hamidian, H. Eisaki, S. Uchida, A. P. Mackenzie, J.C. Davis and P.J. Hirschfeld, Proc. Nat. Acad. Sci. 117, 14805 (2020).
“Functional Form of the Superconducting Critical Temperature from Machine Learning,” S. R. Xie, G. R. Stewart, J. J. Hamlin, P. J. Hirschfeld, and R. G. Hennig, Phys. Rev. B 100, 174513 (2019).
“Raising $T_c$ with Disorder in Spin-Fluctuation Mediated Unconventional Superconductors,” A. Böhmer, P.J. Hirschfeld, and B.M. Andersen, Phys. Rev. Lett. 121, 027002 (2018).
“Discovery of orbitally selective nematic Cooper pairing in FeSe,” P.O. Sprau, A. Kostin, A. Kreisel, A. Böhmer, P.C. Canfield, P.J. Hirschfeld, B.M.Andersen, and J.C. Davis, Science 357, 75 (2017).
Condensed Matter Theory
Office: 2156 NPB