Emerging superconductivity with broken time reversal symmetry inside a superconducting $s$-wave state

Abstract

In general, magnetism and superconductivity are antagonistic to each other. However, there are several families of superconductors, in which superconductivity may coexist with magnetism, and only a few examples are known, when superconductivity itself induces spontaneous magnetism. The most known compounds are Sr${}_2$RuO${}_4$ and some noncentrosymmetric superconductors. Here, we report the finding of a narrow dome of a novel $s+i{s}^{\prime }$ superconducting (SC) phase with broken time-reversal symmetry (BTRS) inside the broad $s$-wave SC region of the centrosymmetric multiband superconductor Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ ($0.7\lesssim x\lesssim 0.85$). We observe spontaneous magnetic fields inside this dome using the muon spin relaxation ($\mu$SR) technique. Furthermore, our detailed specific heat study reveals that the BTRS dome appears very close to a change in the topology of the Fermi surface (Lifshitz transition). With this, we experimentally demonstrate the emergence of a novel quantum state due to topological changes of the electronic system.

28 pages, 11 figures

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• Time-reversal symmetry breaking state near the surface of $s_{\pm }$-superconductor
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Cited by in corpus (66)

• Electronic structure of quantum materials studied by angle-resolved photoemission spectroscopy
• Ironing out the details of unconventional superconductivity
• Split superconducting and time-reversal symmetry-breaking transitions, and magnetic order in Sr${}_2$RuO${}_4$ under uniaxial stress
• On the Remarkable Superconductivity of FeSe and its Close Cousins
• Charge order breaks time-reversal symmetry in CsV${}_3$Sb${}_5$
• Recent progress on superconductors with time-reversal symmetry breaking
• Microscopic evidence for anisotropic multigap superconductivity in the CsV${}_3$Sb${}_5$ kagome superconductor
• Quartic metal: Spontaneous breaking of time-reversal symmetry due to four-fermion correlations in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Evidence of a hidden flux phase in the topological kagome metal CsV${}_3$Sb${}_5$
• Unsplit superconducting and time reversal symmetry breaking transitions in Sr${}_2$RuO${}_4$ under hydrostatic pressure and disorder
• Observation of superconducting vortices carrying a temperature-dependent fraction of the flux quantum
• Observation of Superconductivity Induced Ferromagnetism in an Fe-Chalcogenide Superconductor
• Unveiling unconventional magnetism at the surface of Sr${}_2$RuO${}_4$
• Spectroscopic signatures of time-reversal symmetry breaking superconductivity
• Muon-spin relaxation study of the layered kagome superconductor CsV${}_3$Sb${}_5$
• Perspective on the muon-spin rotation/relaxation under hydrostatic pressure
• Evidence of nodal superconductivity in monolayer 1H-TaS${}_2$ with hidden order fluctuations
• Time-reversal symmetry breaking and multigap superconductivity in the noncentrosymmetric superconductor La${}_7$Ni${}_3$
• Spectroscopic Signatures of Gate-Controlled Superconducting Phases
• Multiorbital singlet pairing and $d+d$ superconductivity
• Supercurrent rectification with time-reversal symmetry broken multiband superconductors
• Calorimetric evidence for two phase transitions in Ba${}_{1-\mathrm{x}}$K${}_{\mathrm{x}}$Fe${}_2$As${}_2$ with fermion pairing and quadrupling states
• Multiple-q current states in a multicomponent superconducting channel
• Supercurrents and spontaneous time-reversal symmetry breaking by nonmagnetic disorder in unconventional superconductors
• Emerging symmetric strain response and weakening nematic fluctuations in strongly hole-doped iron-based superconductors
• Short-range nematic fluctuations in Sr1-xNaxFe2As2 superconductors
• Strain-induced time reversal breaking and half quantum vortices near a putative superconducting tetra-critical point in Sr${}_2$RuO${}_4$
• Magneto-topological transitions in multicomponent superconductors
• Neutron scattering studies on spin fluctuations in Sr${}_2$RuO${}_4$
• Signatures of a surface spin-orbital chiral metal
• Multiband strong-coupling superconductors with spontaneously broken time-reversal symmetry
• Demonstration of $\mathbb{C}{P}^2$ skyrmions in three-band superconductors by self-consistent solutions to a Bogoliubov-de Gennes model
• Effects of intercomponent couplings on the appearance of time-reversal symmetry breaking fermion quadrupling state in two-component London models
• Phase solitons in a weakly coupled three-component superconductor
• Emergent Tetragonality in a Fundamentally Orthorhombic Material
• Effective model and Magnetic Properties of the Resistive Electron Quadrupling State
• Anomalous thermodynamic properties of quantum critical superconductors
• Time-reversal symmetry breaking in superconductors through loop super-current order
• High-order Time-Reversal Symmetry Breaking Normal State
• Detection of collective modes in unconventional superconductors using tunneling spectroscopy
• Frustration driven Josephson phase dynamics
• Spontaneous magnetization in unitary superconductors with time reversal symmetry breaking
• Pseudogap and Strong Pairing Induced by Incipient and Shallow Bands in the Quasi-Two-Dimensional KCa${}_2$Fe${}_4$As${}_4$F${}_2$
• Supercurrent Diode Effect in Josephson Interferometers with Multiband Superconductors
• Time-reversal-symmetry Breaking in the Superconducting State of ScS
• Spin-orbit-coupled superconductivity with spin-singlet non-unitary pairing
• Time-reversal symmetry breaking in superconducting low-carrier-density quasi-skutterudite Lu3Os4Ge13
• Magnetic field behaviour in $s+is$ and $s+id$ superconductors: twisting of applied and spontaneous fields
• Inhomogeneous magnetic multiband superconductors
• Neutron Spin Resonance Near a Lifshitz Transition in Overdoped Ba${}_{0.4}$K${}_{0.6}$Fe${}_2$As${}_2$
• Status of Iron Based Superconductors: characteristics and relevant properties for applications
• Electronic Raman response of a superconductor across a time reversal symmetry breaking phase transition
• Elastoresistivity of heavily hole doped 122 iron pnictides superconductors
• Thermodynamic properties of nodal superconductors close to a magnetic quantum critical point
• Ultrasound evidence for multicomponent superconducting order parameter in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ with electron quadrupling phase
• Observation of vortex stripes in UTe${}_2$
• Spontaneous edge corner currents in $s+is$ superconductors and time reversal symmetry breaking surface states
• Microscopic properties of fractional vortices and domain walls in three-band $s+is$ superconductors
• Thermodynamics of $s_{\pm }-to-s_{++}$ transition in iron pnictides in the vicinity of the Born limit
• Transport anomalies in multiband superconductors near quantum critical point
• Pressure induced superconducting dome in LaNiGa2
• Impurity bands in magnetic superconductors with spin density wave
• Vortex nucleation barriers and stable fractional vortices near boundaries in multicomponent superconductors
• Topological order in higher composites
• Hund's coupling assisted orbital-selective superconductivity in Ba1-xKxFe2As2
• Effective Ionic Valence and Local Magnetic Moment in Kagome Superconductors