Muon spin relaxation and rotation $\left(\mu \mathrm{SR}\right)$ measurements have been performed to study the superconducting and magnetic properties of ${\mathrm{Nb}}_2{\mathrm{PdS}}_5$. Zero-field $\mu \mathrm{SR}$ data show that no sizable spontaneous magnetization arises with the onset of superconductivity in ${\mathrm{Nb}}_2{\mathrm{PdS}}_5$, which indicates that the time-reversal symmetry is probably preserved in the superconducting state of this system. A strong diamagnetic shift is observed in the transverse-field $\mu \mathrm{SR}$ data practically ruling out a dominant triplet-pairing superconducting state in ${\mathrm{Nb}}_2{\mathrm{PdS}}_5$. The temperature dependence of magnetic penetration depth evidences the existence of a single $s$-wave energy gap $\Delta \left(0\right)$ with a gap value of 1.07(4) meV at zero temperature. The ratio $\Delta \left(0\right)/k_{\mathrm{B}}{T}_{\mathrm{c}}=2.02\left(9\right)$ indicates that ${\mathrm{Nb}}_2{\mathrm{PdS}}_5$ should be considered as a moderately strong-coupling superconductor. The magnetic penetration depth at zero temperature is 785(20) nm, indicating a very low superfluid density consistent with the quasi-one-dimensional nature of this system.

• Received 16 January 2015
• Revised 27 February 2015

DOI:https://doi.org/10.1103/PhysRevB.91.100504