Department of Physics | University of Florida

Theory of superconductivity, strongly correlated Fermi systems & electronic disorder.

The Hirschfeld group studies problems of modern many-body theory associated with quantum materials. These are condensed matter systems that cannot be described by the conventional Bloch picture of a single electron moving in a periodic potential. They exhibit remarkable collective phenomena and novel ordered phases, and are expected to be relevant to the next generation of electronic devices. One particular focus is on "unconventional" superconductors, where electron pairing is driven by repulsive Coulomb interactions. Recently, a second focus has been opened on discovery of "extraordinary conventional" superconductors including developing high-throughput computational methods based on density functional theory descriptors.

Hirschfeld group poster 2019

Current group: Front: Mainak,Clara (NBI), Pawan, Laura (SISSA), Peter. Back: Ge, Siddhant, Benjamin, Phil. Missing: Yifu. View research group alumni and collaborators. Funded by U.S. Dept. of Energy and Nat'l Science Foundation.


  • Overdoped cuprates

    It has generally been assumed that the complex cuprate phase diagram, with many different orders intertwined with superconductivity, simplifies in the overdoped limit, where Landau Fermi liquid theory and BCS (d-wave) superconductivity should reign. This view was challenged recently by measurements from the Brookhaven group showing that in high-quality LSCO films, the superfluid density ρs ~ Tc, in contradiction to the BCS prediction for a clean system, which says ρs ~n, independent of Tc. We showed (Lee-Hone et al, PRB 96, 024501 (2017), ibid 98, 054506 , Phys. Rev. Res.2, 013228 (2020)) that this behavior emerges from the little-studied properties of out-of-plane dopant disorder. Comparison of superfluid density vs. Tc for LSCO and Tl-2201. The latter is approximately 3 times cleaner, since the dopants are located further from the CuO2 plane. Recently, we reanalyzed the date using dopant potentials determined from ab initio calcuations.
  • Pair Density Waves

    Scanning tunneling microscopy (STM) provides spectacular real-space images of the surfaces of metals, and has been used to shed light on the superconducting and normal states of high-Tc superconductors. For many years, STM images have revealed the presence of a static density wave order in BSCCO-2212 and 2201, which has been associated with ``charge order" seen by x-rays in several cuprates. There is increasing evidence , however, for the interpretation of these phenomena in terms of ``Pair Density Waves" (PDW), a modulated pairing state that drives charge order if it coexists with uniform d-wave superconductivity. We have devloped the "BdG+Wannier" method to predict sub-unit-cell conductance maps for comparison with STM images, and used it to create images of an 8 unit cell pair density wave state coexisting with d-wave superconductivity, within a Gutzwiller approximation for the t-J model (Choubey et al, NJP 19, 013028 (2017), PNAS 117,14805 (2020), Wang et al., Nat. Comm. 12, 6087 (2021) ). Predicted conductance map at bias equal to the maximum gap, compared to experiment.


© 2015 Peter J. Hirschfeld. All rights reserved.

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