Enhanced superconducting pairing strength near a nonmagnetic nematic quantum critical point

Abstract

The quest for high-temperature superconductivity at ambient pressure is a central issue in physics. In this regard, the relationship between unconventional superconductivity and the quantum critical point (QCP) associated with the suppression of some form of symmetry-breaking order to zero temperature has received particular attention. The key question is how the strength of the electron pairs changes near the QCP, and this can be verified by high-field experiments. However, such studies are limited mainly to superconductors with magnetic QCPs, and the possibility of unconventional mechanisms by which nonmagnetic QCP promotes strong pairing remains a nontrivial issue. Here, we report systematic measurements of the upper critical field $H_{c2}$ in nonmagnetic FeSe${}_{1-x}$Te${}_x$ superconductors, which exhibit a QCP of electronic nematicity characterized by spontaneous rotational-symmetry breaking. As the magnetic field increases, the superconducting phase of FeSe${}_{1-x}$Te${}_x$ shrinks to a narrower dome surrounding the nematic QCP. The analysis of $H_{c2}$ reveals that the Pauli-limiting field is enhanced toward the QCP, implying that the pairing interaction is significantly strengthened via nematic fluctuations emanated from the QCP. Remarkably, this nonmagnetic nematic QCP is not accompanied by a divergent effective mass, distinct from the magnetically mediated pairing. Our observation opens up a nonmagnetic route to high-temperature superconductivity.

6 pages, 4 figures

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• Bulk and surface Dirac states accompanied by two superconducting domes in FeSe-based superconductors
• On the size of superconducting islands on the density-wave background in organic metals
• Correlation between unconventional superconductivity and strange metallicity revealed by operando superfluid density measurements
• Transfer learning from Hermitian to non-Hermitian quantum many-body physics
• Coherence Length of Electronic Nematicity in Iron-Based Superconductors
• Non-Fermi liquid transport and strong mass enhancement near the nematic quantum critical point in FeSe${}_x$Te${}_{1-x}$ thin films
• Odd-parity quadrupole order and induced nonreciprocal transport in the kagome metal CsTi${}_3$Bi${}_5$ driven by quantum interference
• Systematic evolution of superconducting pairing strength and Seebeck coefficients in correlated infinite-layer La${}_{1-x}$Sr${}_x$NiO${}_2$
• Superconductivity and the quasiparticle mass enhancement near the CDW critical point using Bethe-Salpeter method: Application to cuprates
• Reaching Quantum Critical Point by Adding Non-magnetic Disorder in Single Crystals of Superconductor $({\text{Ca}}_x{\text{Sr}}_{1-x}{)}_3{\text{Rh}}_4{\text{Sn}}_{13}$
• Superconductivity near an Ising nematic quantum critical point in two dimensions