Anomalous critical fields in quantum critical superconductors

Abstract

Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ is perhaps the clearest example to date of a high temperature quantum critical superconductor, and so it is a particularly suitable system in which to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields strongly violate the expectations from the conventional theory taking into account the observed mass enhancement near the QCP. These anomalous behaviours of the critical fields imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realised in quantum critical superconductors.

9 pages

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• SO(5) Theory of Antiferromagnetism and Superconductivity
• Vortex Imaging in the pi-Band of Magnesium Diboride
• Direct measurement of the upper critical field in a cuprate superconductor
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Cited by in corpus (32)

• Dome-shaped magnetic order competing with high-temperature superconductivity at high pressures in FeSe
• Nematicity, magnetism and superconductivity in FeSe
• Quantum sensing of local magnetic field texture in strongly correlated electron systems under extreme conditions
• Doping-dependent critical current properties in K, Co, and P-doped BaFe2As2 single crystals
• Ultra-high critical current densities, the vortex phase diagram and the effect of granularity of the stoichiometric high-Tc superconductor, CaKFe${}_4$As${}_4$
• Ultra-high critical current densities of superconducting YBa${}_2$Cu${}_3$O${}_{7-\delta }$ thin films in the overdoped state
• Dome of magnetic order inside the nematic phase of sulfur-substituted FeSe under pressure
• Measurements of the lower critical field of superconductors using NV centers in diamond optical magnetometry
• Superfluid density and carrier concentration across a superconducting dome: the case of SrTi${}_{1-x}$Nb${}_x$O${}_3$
• Full-gap superconductivity robust against disorder in heavy-fermion CeCu2Si2
• High-field transport properties of a P-doped BaFe2As2 film on technical substrate
• The electron-phonon coupling constant and the Debye temperature in polyhydrides of thorium, hexadeuteride of yttrium, and metallic hydrogen phase III
• Unusually high critical current of clean P-doped BaFe2As2 single crystalline thin film
• Quantum phase transition inside the superconducting dome of Ba(Fe${}_{1-x}$Co${}_x$)${}_2$As${}_2$ probed by optical magneto-sensing using NV-centers in diamond
• Microscopic Parameters from High-Resolution Specific Heat Measurements on Overdoped BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$ Single Crystals
• Superconducting fluctuations in isovalently-substituted BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$: Possible observation of multiband effects
• London penetration depth measurements using tunnel diode resonators
• Muon spin rotation and infrared spectroscopy study of magnetism and superconductivity in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Evolution of quasiparticle excitations with critical mass enhancement in superconducting AFe2As2 (A = K, Rb, and Cs)
• Thermal effects in non-Fermi liquid superconductivity
• Anisotropic Enhancement of Lower Critical Field in Ultraclean Crystals of Spin-Triplet Superconductor UTe2
• Peak in the critical current density in (Ca${}_x$Sr${}_{1-x}$)${}_3$Rh${}_4$Sn${}_{13}$ tuned towards the structural quantum critical point
• Selective mass enhancement close to the quantum critical point in BaFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Unveiling the Physics of the Mutual Interactions in Paramagnets
• Mass enhancement in multiple bands approaching optimal doping in a high-temperature superconductor
• Thermodynamic properties of nodal superconductors close to a magnetic quantum critical point
• Determination of the magnetic penetration depth with measurements of the vortex-penetration field for type-II superconductors
• Josephsonic diagnostic of competing orders in quantum critical multiband superconductors
• Boost of critical current density near quantum critical points in FeSe-Based superconductors with two superconducting domes
• Reaching Quantum Critical Point by Adding Non-magnetic Disorder in Single Crystals of Superconductor $({\text{Ca}}_x{\text{Sr}}_{1-x}{)}_3{\text{Rh}}_4{\text{Sn}}_{13}$
• Breakdown of the critical state in the ferromagnetic superconductor EuFe${}_2$(As${}_{1-x}$P${}_x$)${}_2$
• Determination of the London penetration depth with the tunnel diode oscillator technique