Evidences of nodeless multigap superconductivity in 2H-Pd_xTaSe₂ from thermal transport

2H-TaSe₂ is one of unique transition metal dichalcogenides which exhibits an incommensurate charge density wave (ICDW) state at ≈ 122 K followed by a commensurate charge density wave (CCDW) state at ≈ 90 K and superconductivity at T_C ~ 0.14 K. Recently, it was found that upon systematic intercalation of Pd ions into 2H-TaSe₂, the CCDW order is destabilized more rapidly than ICDW to indicate a hidden quantum phase transition point at x ~ 0.09-0.10. Moreover, T_C shows a dramatic enhancement up to 3.3 K at x = 0.08, ~24 times of T_C in 2H-TaSe₂ [1]. In this work, we measured the in-plane thermal conductivity (k) of a 2H-Pd_xTaSe₂ single crystals with T_c ~ 3.13 K down to 100 mK. In zero magnetic field, the absence of the residual linear term in κ₀/T at T → 0, supports the nodeless superconducting gap feature. Moreover, magnetic field dependence of the normalized residual linear term (κ₀(H)/T)/(κ_N/T)) exhibits similar behavior as observed in the multiband superconductor like NbSe₂ [2]. These results strongly support the presence of multiple nodeless superconducting gaps in 2H-Pd_xTaSe₂.
References
[1] D. Bhoi et al., Scientific Reports 6, 24068 (2016)
[2] E. Boaknin et al., Physical Review Letters 90, 117003 (2003)