Prediction of time-reversal-symmetry breaking fermionic quadrupling condensate in twisted bilayer graphene

Abstract

Recent mean-field calculations suggest that the superconducting state of twisted bilayer graphene exhibits either a nematic order or a spontaneous breakdown of the time-reversal symmetry. The two-dimensional character of the material and the large critical temperature relative to the Fermi energy dictate that the material should have significant fluctuations. We study the effects of these fluctuations using Monte Carlo simulations. We show that in a model proposed earlier for twisted bilayer graphene there is a fluctuation-induced phase with quadrupling fermionic order for all considered parameters. This four-electron condensate, instead of superconductivity, shows a spontaneous breaking of time-reversal symmetry. Our results suggest that twisted bilayer graphene is an especially promising platform to study different types of condensates, beyond the pair-condensate paradigm.

12 pages, 8 figures

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Cited by in corpus (12)

• Stabilizing fluctuating spin-triplet superconductivity in graphene via induced spin-orbit coupling
• Josephson diode effects in twisted nodal superconductors
• Calorimetric evidence for two phase transitions in Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ with fermion pairing and quadrupling states
• Electron-K-Phonon Interaction In Twisted Bilayer Graphene
• Vestigial singlet pairing in a fluctuating magnetic triplet superconductor: Applications to graphene moiré systems
• Charge-4$e$ Superconductivity in a Hubbard model
• Cooper quartets in interacting hybrid superconducting systems
• Nodal Nematic Superconductivity in Multiple-Flat-Band Land
• Microscopic theory of electron quadrupling condensates
• Revisiting vestigial order in nematic superconductors: gauge-field mechanisms and model constraints
• Three-dimensional flat bands and possible interlayer triplet pairing superconductivity in the alternating twisted NbSe${}_2$ moiré bulk
• Fate of Berezinskii-Kosterlitz-Thouless Paired Phase in Coupled $XY$ Models