Anisotropic gapping of topological Weyl rings in the charge-density-wave superconductor InTaSe.

Topological materials and topological phases have recently become a hot topic in condensed matter physics. In this work, we report an In-intercalated transition-metal dichalcogenide InTaSe (named 112 system), a topological nodal-line semimetal in the presence of both charge density wave (CDW) and superconductivity. In the x = 0.58 sample, the 2×3 commensurate CDW (CCDW) and the 2×2 CCDW are observed below 116 and 77 K, respectively. Consistent with theoretical calculations, the spin-orbital coupling gives rise to two twofold-degenerate nodal rings (Weyl rings) connected by drumhead surface states, confirmed by angle-resolved photoemission spectroscopy. Our results suggest that the 2×2 CCDW ordering gaps out one Weyl ring in accordance with the CDW band folding, while the other Weyl ring remains gapless with intact surface states. In addition, superconductivity emerges at 0.91 K, with the upper critical field deviating from the s-wave behavior at low temperature, implying possibly unconventional superconductivity. Therefore, we think this type of the 112 system may possess abundant physical states and offer a platform to investigate the interplay between CDW, nontrivial band topology and superconductivity.