Quasiparticle Heat Transport in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$: Evidence for a k-dependent Superconducting Gap without Nodes

Abstract

The thermal conductivity $\kappa$ of the iron-arsenide superconductor Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ ($T_c\simeq$ 30 K) was measured in single crystals at temperatures down to $T\simeq 50$ mK ($\simeq T_c$/600) and in magnetic fields up to $H=15$ T ($\simeq H_{c2}$/4). A negligible residual linear term in $\kappa /T$ as $T\to 0$ shows that there are no zero-energy quasiparticles in the superconducting state. This rules out the existence of line and in-plane point nodes in the superconducting gap, imposing strong constraints on the symmetry of the order parameter. It excludes d-wave symmetry, drawing a clear distinction between these superconductors and the high-$T_c$ cuprates. However, the fact that a magnetic field much smaller than $H_{c2}$ can induce a residual linear term indicates that the gap must be very small on part of the Fermi surface, whether from strong anisotropy or band dependence, or both.

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Cited by in corpus (18)

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• High-temperature superconductivity stabilized by electron-hole interband coupling in collapsed tetragonal phase of KFe2As2 under high pressure
• Distinguishing between $s+id$ and $s+is$ pairing symmetries in multiband superconductors through spontaneous magnetization pattern induced by a defect
• ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism
• Heat transport in RbFe2As2 single crystal: evidence for nodal superconducting gap
• Distinct high-T transitions in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Anisotropic fluctuations and quasiparticle excitations in FeSe_0.5Te_0.5
• Competition between superconductivity and magnetic/nematic order as a source of anisotropic superconducting gap in underdoped Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Superconductivity and electronic fluctuations in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ studied by Raman scattering
• Skyrmionic chains and lattices in $s+id$ superconductors
• Infrared probe of the gap evolution across the phase diagram of Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$
• Comment on "Isoelectronic Ru substitution at Fe-site in Sm(Fe${}_{1-x}$Ru${}_x$)AsO${}_{0.85}$F${}_{0.15}$ compound and its effects on structural, superconducting and normal state properties" (arXiv:1004.1978)
• Superconductivity In K- And Na- Doped Bafe2as2: What Can We Learn From Heat Capacity And Pressure Dependence of Tc
• Ultrasound evidence for multicomponent superconducting order parameter in Ba${}_{1-x}$K${}_x$Fe${}_2$As${}_2$ with electron quadrupling phase
• Effect of controlled point-like disorder induced by 2.5 MeV electron irradiation on nematic resistivity anisotropy of hole-doped (Ba,K)Fe${}_2$As${}_2$