Incoherent Cooper pairing and pseudogap behavior in single-layer FeSe/SrTiO${}_3$

Abstract

In many unconventional superconductors, the presence of a pseudogap - a suppression in the electronic density of states extending above the critical temperature - has been a long-standing mystery. Here, we employ combined \textit{in situ} electrical transport and angle-resolved photoemission spectroscopy (ARPES) measurements to reveal an unprecedentedly large pseudogap regime in single-layer FeSe/SrTiO${}_3$, an interfacial superconductor where incoherent Cooper pairs are initially formed above $T_{\Delta }$ $\approx$ 60 K, but where a zero resistance state is only achieved below $T_0$ $<$ 30 K. We show that this behavior is accompanied by distinct transport signatures of two-dimensional phase fluctuating superconductivity, suggesting a mixed vortex state hosting incoherent Cooper pairs which persist well above the maximum clean limit $T_c$ of $\approx$ 40 K. Our work establishes the critical role of reduced dimensionality in driving the complex interplay between Cooper pairing and phase coherence in two-dimensional high-$T_c$ superconductors, providing a paradigm for understanding and engineering higher-$T_c$ interfacial superconductors.

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• Fluctuating Nature of Light-Enhanced $d$-Wave Superconductivity: A Time-Dependent Variational Non-Gaussian Exact Diagonalization Study
• Interfacial Electron-Phonon Coupling Constants Extracted from Intrinsic Replica Bands in Monolayer FeSe/SrTiO${}_3$
• An Integrated Quantum Material Testbed with Multi-Resolution Photoemission Spectroscopy
• Quasi two-dimensional nature of high-Tc superconductivity in iron-based (Li,Fe)OHFeSe
• Twisted-bilayer FeSe and the Fe-based superlattices
• Interface superconductivity in FeSe thin films on SrTiO${}_3$grown by the PLD technique
• Higher-Order Spin-Hole Correlations around a Localized Charge Impurity
• Positive and negative chemical pressure effects investigated in electron-doped FeSe films with an electric-double-layer structure
• Probing the Berezinskii-Kosterlitz-Thouless vortex unbinding transition in two-dimensional superconductors using local noise magnetometry
• Checkerboard order state in superconducting FeSe/SrTiO3(001) monolayer
• Entanglement Witness for Indistinguishable Electrons using Solid-State Spectroscopy
• Anisotropy of upper critical fields and interface superconductivity in FeSe/SrTiO3 grown by PLD
• Superconducting fluctuations and charge-4$e$ plaquette state at strong coupling
• Strong ferromagnetic fluctuations in a doped checkerboard lattice
• Modulation doping of the FeSe monolayer on SrTiO${}_3$
• In-situ visualization of local distortions in the high-$T_c$ molecule-intercalated $L{i}_x(C_5{H}_{5}N{)}_{y}F{e}_{2-z}S{e}_2$ superconductor
• Temperature dependence and limiting mechanisms of the upper critical field of FeSe thin films
• Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO${}_{0.5}$F${}_{0.5}$BiS${}_2$
• Study on fluctuations of interface-enhanced superconductivity in ultrathin FeSe/SrTiO3 by the Nernst effect
• Spin correlations in the parent phase of Li${}_{1-x}$Fe${}_x$ODFeSe
• Inferior interfacial superconductivity in 1 UC FeSe/SrVO${}_3$/SrTiO${}_3$ with screened interfacial electron-phonon coupling
• Suppression and revival of superconducting phase coherence in monolayer FeSe/SrTiO${}_3$
• Revealing quantum phase string effect in doped Mott-insulator: a tensor network state approach
• Unconventional incommensurate epitaxy of superconducting FeSe films on SrTiO${}_3$
• Fabrication of oxide/FeSe multilayer films using the PLD technique
• The thermoelectric conversion efficiency problem: Insights from the electron gas thermodynamics close to a phase transition
• Spectroscopic evidence of disorder-induced quantum phase transitions in monolayer Fe(Te,Se) superconductor
• Non-thermal pairing glue of electrons in the steady state