Pseudogap formation in organic superconductors

Abstract

The condensation of paired fermions into superfluid states changes progressively depending on the coupling strength. At the midpoint of the crossover between Bardeen--Cooper--Schrieffer (BCS) weak-coupling and Bose--Einstein condensate (BEC) strong-coupling limits, paired fermions condensate most robustly, thereby leading to the emergence of a pseudogap due to enhanced pairing fluctuations. In the case of electrons in solids, excessively strong interactions often induce competing electronic orders instead of strong-coupling superconductivity, and experimental comprehension of the pseudogap remains incomplete. In this study, we provide experimental evidence demonstrating the opening of a pseudogap, marking the incipient stage of the BCS-BEC crossover in the organic system $\kappa$-(BEDT-TTF)${}_2$$X$. By controlling electron correlations, we investigate the thermodynamic properties of the BCS-BEC crossover and pseudogap phase. Since the superconductivity of $\kappa$-(BEDT-TTF)${}_2$$X$ arises from a simple Fermi liquid that does not exhibit any other electronic orders, our study shed light on the inherent nature of the BCS-BEC crossover.

References in corpus (21)

• Magic-angle graphene superlattices: a new platform for unconventional superconductivity
• The pseudogap in high-temperature superconductors: an experimental survey
• Observation of Bose-Einstein Condensation of Molecules
• Thermodynamics of the BCS-BEC crossover
• Observation of pseudogap behavior in a strongly interacting Fermi gas
• BCS-BEC Crossover and the Unitary Fermi Gas
• Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover
• Gate-controlled BCS-BEC crossover in a two-dimensional superconductor
• Specific heat measurements of the gap structure of the organic superconductors kappa-(ET)_2Cu[N(CN)_2]Br and kappa-(ET)_2Cu(NCS)_2
• Upper bounds on the superfluid stiffness and superconducting $T_c$: Applications to twisted-bilayer graphene and ultra-cold Fermi gases
• Superconducting transitions from the pseudogap state: d-wave symmetry, lattice, and low-dimensional effects
• Spin-charge-entangled non-Fermi liquid in a candidate material for a doped spin liquid
• Impurity Effect on the In-plane Penetration Depth of the Organic Superconductors $\kappa$-(BEDT-TTF)${}_{2}X$ ($X$ = Cu(NCS)${}_2$ and Cu[N(CN)${}_2$]Br)
• Mott-driven BEC-BCS crossover in a doped spin liquid candidate, kappa-(BEDT-TTF)4Hg2.89Br8
• Magic gap ratio for optimally robust fermionic condensation and its implications for high-Tc superconductivity
• Specific heat and effects of pairing fluctuations in the BCS-BEC crossover regime of an ultracold Fermi gas
• Extraordinary $\pi$-Electron Superconductivity Emerging from a Quantum Spin Liquid
• Absence of a BCS-BEC crossover in the cuprate superconductors
• Mixed pairing symmetry in κ-(BEDT-TTF)_2 X organic superconductors from ultrasonic velocity measurements
• Emergent anisotropy in the Fulde-Ferrell-Larkin-Ovchinnikov state
• Symmetry change of $d$-wave superconductivity in $\kappa$-type organic superconductors

Cited by in corpus (4)

• Superconductivity and Mottness in Organic Charge Transfer Materials
• Possibility of BCS-BEC crossover in $\kappa$-type organic superconductors
• Removal of excess iron by annealing processes and emergence of bulk superconductivity in sulfur-substituted FeTe
• The Frenkel line and the pseudogap: an analogy between classical and electronic fluids