Bypassing the lattice BCS-BEC crossover in strongly correlated superconductors: resilient coherence from multiorbital physics

Abstract

Superconductivity emerges from the spatial coherence of a macroscopic condensate of Cooper pairs. Increasingly strong binding and localization of electrons into these pairs compromises the condensate's phase stiffness, thereby limiting critical temperatures -- a phenomenon known as the BCS-BEC crossover in lattice systems. In this study, we demonstrate enhanced superconductivity in a multiorbital model of alkali-doped fullerides (A${}_3$C${}_{60}$) that goes beyond the limits of the lattice BCS-BEC crossover. We identify that the interplay of strong correlations and multiorbital effects results in a localized superconducting state characterized by a short coherence length but robust stiffness and a domeless rise in critical temperature with increasing pairing interaction. To derive these insights, we introduce a new theoretical framework allowing us to calculate the fundamental length scales of superconductors, namely the coherence length (${\xi }_0$) and the London penetration depth (${\lambda }_{\mathrm{L}}$), even in presence of strong electron correlations.

main: 12 pages, 5 figures, 1 table | supplemental: 27(+1), 9 figures, 1 table

References in corpus (26)

• Continuous-time Monte Carlo methods for quantum impurity models
• Tunable Phase Boundaries and Ultra-Strong Coupling Superconductivity in Mirror Symmetric Magic-Angle Trilayer Graphene
• Strong electronic correlations from Hund's coupling
• Supercurrent diode effect and finite momentum superconductivity
• Superfluidity and Quantum Geometry in Twisted Multilayer Systems
• Band geometry, Berry curvature and superfluid weight
• Superconducting materials: Challenges and opportunities for large-scale applications
• Hund's coupling key role in multi-orbital correlations
• Modeling the Unconventional Superconducting Properties of Expanded A${}_3$C${}_{60}$ Fullerides
• Finite-momentum Cooper pairing in proximitized altermagnets
• Fluctuation diagnostics of the electron self-energy: Origin of the pseudogap physics
• Gate-controlled BCS-BEC crossover in a two-dimensional superconductor
• Orbital Fulde-Ferrell-Larkin-Ovchinnikov state in an Ising superconductor
• Quenched pair breaking by interlayer correlations as a key to superconductivity in La${}_3$Ni${}_2$O${}_7$
• When Superconductivity Crosses Over: From BCS to BEC
• NMR study of the Mott transitions to superconductivity in the two Cs_3C_60 phases
• Two-band superfluidity from the BCS to the BEC limit
• Superconductivity in the two-band Hubbard model
• Molecular Pairing in Twisted Bilayer Graphene Superconductivity
• Dynamic Superconductivity Responses in Photo-excited Optical Conductivity and Nernst Effect
• Absence of a BCS-BEC crossover in the cuprate superconductors
• Suppression of fluctuations in a two-band superconductor with a quasi-1D band
• Superconductivity enhanced by pair fluctuations between wide and narrow bands
• High-$T_c$ Berezinskii-Kosterlitz-Thouless transition in 2D superconducting systems with coupled deep and quasi-flat electronic bands with van Hove singularities
• Test for BCS-BEC Crossover in the Cuprate Superconductors
• Unconventional orbital ordering and emergent dimensional reduction in fulleride superconductors

Cited by in corpus (4)

• Strong-coupling high-$T_{\mathrm{c}}$ superconductivity in doped correlated band insulators
• Quantum many-body solver using artificial neural networks and its applications to strongly correlated electron systems
• Possibility of BCS-BEC crossover in $\kappa$-type organic superconductors
• Superconductor-Insulator transition in a two-orbital attractive Hubbard model with Hund's exchange