RQMP Research Seminar

New signatures of the pseudogap phase of cuprate superconductors

Louis Taillefer

Institut Quantique
Université de Sherbrooke

The pseudogap phase of cuprate superconductors is arguably the most enigmatic phase of quantum matter. We aim to shed new light on this phase by investigating the non-superconducting ground state of several cuprate materials at low temperatures across a wide doping range, suppressing superconductivity with a magnetic field [1].

Hall effect and thermal conductivity measurements across the pseudogap critical doping p^* reveal a sharp drop in carrier density n from n = 1 + p above p^* to n = p below p^* [2,3], signaling a major transformation of the Fermi surface. From specific heat measurements, we observe the classic thermodynamic signatures of quantum criticality: the electronic specific heat C el shows a sharp peak at p^*, where it varies in temperature as C el ~ – T logT [4]. At p^* and just above, the electrical resistivity is linear in T at low T, with an inelastic scattering rate that obeys the Planckian limit [5]. Finally, the pseudogap phase is found to have a large negative thermal Hall conductivity, which extends to zero doping [6]. We show that the pseudogap phase makes phonons become chiral [7].

Understanding the mechanisms responsible for these various new signatures will help elucidate the nature of the pseudogap phase.

[1] Proust & Taillefer, Annual Review of Condensed Matter Physics 10, 409 (2019); arXiv:1807.05074.
[2] Badoux et al., Nature 531, 210 (2016).
[3] Collignon et al., Physical Review B 95, 224517 (2017).
[4] Michon et al., Nature 567, 218 (2019).
[5] Legros et al., Nature Physics 15, 142 (2019).
[6] Grissonnanche et al., Nature 571, 376 (2019).
[7] Grissonnanche et al., Nature Physics (in press); arXiv:2003.00111