Dresden 2026 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 56: Superconductivity: Theory I

TT 56.11: Vortrag

Mittwoch, 11. März 2026, 17:45–18:00, CHE/0089

Strong-coupling superconductivity near Gross-Neveu quantum criticality in Dirac systems — •Veronika Stangier¹, Daniel Sheehy², and Jörg Schmalian¹ — ¹Karlsruhe Institute for Technology, Karlsruhe, Germany — ²Louisiana State University, Baton Rouge, USA

We investigate superconductivity in two-dimensional massless Dirac fermions at charge neutrality, coupled to bosonic collective modes via a Yukawa interaction. Despite the absence of carriers at zero temperature, we uncover the surprising possibility that such systems can become superconducting near a Gross-Neveu quantum critical point. Remarkably, superconductivity emerges precisely when the fermionic excitations lose coherence - once their anomalous dimension in the normal state becomes sufficiently large. In other words, well-defined quasiparticles fail to superconduct, whereas strongly incoherent ones can. To capture this behavior, we develop a general framework for four-component Dirac systems and derive explicit algebraic criteria for the onset of pairing. Within this description, different bosonic modes - classified by their transformation under time-reversal and internal symmetries - select distinct superconducting channels. We then apply this approach to Dirac models of spin-orbit-coupled systems with orbitals of opposite parity and extend it to analyze superconductivity in moiré Dirac materials such as double-bilayer WSe₂ and twisted bilayer graphene.

Keywords: Twisted Materials; Gross-Neveu transition; Strongly correlated electrons; Theory