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Low-temperature thermal conductivity measurements were performed on single crystals of TlNi2Se2, a nickel chalcogenide heavy-electron superconductor with Tc ≃ 3.7 K. In zero field, the residual electronic contribution at T → 0 K (k0/T ) was well separated from the total thermal conductivity, which is less than 0.45% of its normal-state value. Such a tiny residual k0/T is unlikely contributed by the nodal quasiparticles. The nodeless gap structure is supported by the very weak field dependence of k0(H)/T in low magnetic fields. In the whole field range, k0(H)/T exhibits an S-shaped curve, as in the case of nickel pnictides BaNi2As2 and SrNi2P2. This common feature of nickel-based superconductors can be explained by multiple nodeless superconducting gaps. [ABSTRACT FROM AUTHOR]

We measured the low-temperature thermal conductivity of a layered superconductor with quasi-one-dimensional characteristics, the ternary telluride Ta4Pd3Te16 with a transition temperature Tc≈4.3 K. The significant residual linear term of thermal conductivity in zero magnetic field and its rapid field dependence provide evidence for nodes in the superconducting gap. By measuring resistivity under pressure, we reveal a superconducting dome in the temperature-pressure phase diagram. The existence of gap nodes and a superconducting dome suggest unconventional superconductivity in Ta4Pd3Te16, which may relate to a charge-density-wave instability in this low-dimensional compound. [ABSTRACT FROM AUTHOR]

We report resistivity ρ and thermal conductivity K measurements on Ca³Ir4Sn13 single crystals, in which superconductivity with Tc ≈ 7 K was claimed to coexist with ferromagnetic spin fluctuations. Among three crystals, only one crystal shows a small hump in resistivity near 20 K, which was previously attributed to the ferromagnetic spin fluctuations. The other two crystals show the ρ ~ T² Fermi-liquid behavior at low temperature. For both single crystals with and without the resistivity anomaly, the residual linear term K0/ T is negligible in zero magnetic field. In low fields, K0(H)/T shows a slow field dependence. These results demonstrate that the superconducting gap of Ca3lr4Sn13 is nodeless and thus rule out a nodal gap caused by ferromagnetic spin fluctuations. [ABSTRACT FROM AUTHOR]

We report low-temperature heat transport measurements on superconducting iron sulfide FeS with Tc∷5 K, which has the same crystal structure and similar electronic band structure to the superconducting iron selenide FeSe. In zero magnetic field, a significant residual linear term κ0/T is observed. At low field, κ0/T increases rapidly with increasing field. These results suggest a nodal superconducting gap in FeS. We compare it with the sister compound FeSe and other iron-based superconductors with nodal gaps. [ABSTRACT FROM AUTHOR]

In the heavy-fermion superconductor Ce1-xYbxCoIn5, Yb doping was reported to cause a possible change from nodal d-wave superconductivity to a fully gapped d-wave molecular superfluid of composite pairs near x?≈0.07 (nominal value xnom=0.2). Here we present systematic thermal conductivity measurements on Ce1-xYbxCoIn5 (x=0.013, 0.084, and 0.163) single crystals. The observed finite residual linear term k0/T is insensitive to Yb doping, verifying the universal heat conduction of the nodal d-wave superconducting gap in Ce1-xYbxCoIn5. Similar universal heat conduction is also observed in the CeCo(In1-yCdy)5 system. These results reveal a robust nodal d-wave gap in CeCoIn5 upon Yb or Cd doping. [ABSTRACT FROM AUTHOR]