Multiband Superconductivity in KFe2As2: Evidence for one Isotropic and several Liliputian Energy Gaps

Abstract

We report a detailed low-temperature thermodynamic investigation (heat capacity and magnetization) of the superconducting state of KFe2As2 for H || c axis. Our measurements reveal that the properties of KFe2As2 are dominated by a relatively large nodeless energy gap (Delta?0 = 1.9 kBTc) which excludes dx2-y2 symmetry. We prove the existence of several additional extremely small gaps (?Delta0 < 1.0 kBTc) that have a profound impact on the low-temperature and low-field behavior, similar to MgB2, CeCoIn5 and PrOs4Sb12. The zero-field heat capacity is analyzed in a realistic self-consistent 4-band BCS model which qualitatively reproduces the recent laser ARPES results of Okazaki et al. (Science 337 (2012) 1314). Our results show that extremely low-temperature measurements, i.e. T < 0.1 K, will be required in order to resolve the question of the existence of line nodes in this compound.

7 pages, 6 figures

References in corpus (13)

• Unconventional pairing originating from disconnected Fermi surfaces in superconducting LaFeAsO${}_{1-x}$F${}_x$}
• Observation of Fermi-surface-dependent nodeless superconducting gaps in Ba0.6K0.4Fe2As2
• Magnetism, superconductivity, and pairing symmetry in Fe-based superconductors
• Funtional Renormalization Group Study of the Pairing Symmetry and Pairing Mechanism of the FeAs Based High Temperature Superconductors
• Vortex Imaging in the pi-Band of Magnesium Diboride
• Momentum dependence of the superconducting gap in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Pairing State with a time-reversal symmetry breaking in FeAs based superconductors
• A review of two-band superconductivity: materials and effects on the thermodynamic and reversible mixed-state properties
• Inter-pocket pairing and gap symmetry in Fe-based superconductors with only electron pockets
• Incommensurate spin fluctuations in hole-overdoped superconductor KFe2As2
• Vortex studies in superconducting Ba(Fe0.93Co0.07)2As2
• Gapless Fermi Surfaces in Superconducting CeCoIn5?
• Gapless Fermi Surfaces in anisotropic multiband superconductors in magnetic field

Cited by in corpus (27)

• Superconductivity-induced reentrance of orthorhombic distortion in Ba1-xKxFe2As2
• Thermodynamic evidence for the Fulde-Ferrell-Larkin-Ovchinnikov state in the KFe2As2 superconductor
• Strong Correlations, Strong Coupling and s-wave Superconductivity in Hole-doped BaFe2As2 Single Crystals
• Complex phase diagram of Ba${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$: a multitude of phases striving for the electronic entropy
• Energy Gap Evolution Across the Superconductivity Dome in Single Crystals of (Ba${}_{1-x}$K${}_x$)Fe${}_2$As${}_2$
• Hund interaction, spin-orbit coupling and the mechanism of superconductivity in strongly hole-doped iron pnictides
• Superconductivity with broken time reversal symmetry in ion irradiated Ba${}_{0.27}$K${}_{0.73}$Fe${}_2$As${}_2$ single crystals
• Searching for gap zeros in Sr2RuO4 via field-angle-dependent specific-heat measurement
• Nematic superconducting state in iron pnictide superconductors
• Superconductivity of magnesium diboride
• Unconventional superconductivity in the layered iron germanide YFe${}_2$Ge${}_2$
• Upper critical field of KFe2As2 under pressure: A test for the change in the superconducting gap structure
• Using electron irradiation to probe iron - based superconductors
• Nodal gaps in the nematic superconductor FeSe from heat capacity
• Lower critical field and SNS-Andreev spectroscopy of 122-arsenides: Evidence of nodeless superconducting gap
• Multi-band effects on Fulde-Ferrell-Larkin-Ovchinnikov states of Pauli-limited superconductors
• Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2
• Pressure dependence of coherence-incoherence crossover behavior in KFe2As2 observed by resistivity and 75As-NMR/NQR
• Evolution of quasiparticle excitations with critical mass enhancement in superconducting AFe2As2 (A = K, Rb, and Cs)
• Unconventional bulk superconductivity in YFe${}_2$Ge${}_2$ single crystals
• Superconducting properties of K${}_{1-x}$Na${}_x$Fe${}_2$As${}_2$ under pressure
• Observation of the Non-linear Meissner Effect
• Constraints on the total coupling strength to bosons in iron based superconductors
• Mass enhancements and band shifts in strongly hole overdoped Fe-based pnictide superconductors: KFe${}_2$As${}_2$ and CsFe${}_2$As${}_2$
• Orbital and Pauli limiting effects in heavily doped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Specific heat in strongly hole-doped Iron-based superconductors
• Consistent picture of the octet-nodal gap and its evolution with doping in heavily overdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$