Josephson-like interlayer transport and absence of charge-density-wave signatures in the misfit-layer superconductor (PbS)1.16TaS2

Abstract

We investigate the misfit-layer superconductor (PbS)1.16TaS2, a bulk natural heterostructure comprising alternating PbS and 1H-TaS2 layers. X-ray diffraction, atomically resolved transmission electron microscopy, and anisotropic magnetotransport measurements indicate that the out-of-plane superconducting coherence length is comparable to the interlayer spacing between adjacent 1H-TaS2 sheets, placing the system in the quasi-two-dimensional superconducting regime. Interlayer (magneto)transport further exhibits characteristic peak features consistent with contributions from quasiparticle and Cooper-pair tunneling. In addition, the V–I curves for I//c under B//ab reveal step-like features and negative differential resistance consistent with resonant Josephson-vortex dynamics and associated nonequilibrium instability. These observations support Josephson-like interlayer coupling between the naturally stacked superconducting layers of (PbS)1.16TaS2. Combined resistivity and Raman measurements reveal no detectable charge-density-wave (CDW) signatures. In contrast to CDW-bearing 2H-TaS2, which superconducts only below TC ≈ 0.8 K, (PbS)1.16TaS2 shows an enhanced TC ≈ 3.04 K, consistent with a competing relationship between CDW order and superconductivity. The present findings establish (PbS)1.16TaS2, and potentially related superconducting misfit derivatives, as a versatile platform for studying bulk quasi-two-dimensional superconductivity and associated emergent phenomena, with prospects for Josephson-junction-based devices.