具有拓扑外尔环的电荷密度波超导体In_(x)TaSe_(2)

Anisotropic gapping of topological Weyl rings in the charge-density-wave superconductor In_(x)TaSe_(2)

新型拓扑材料和拓扑相的探索是近年来凝聚态物理中的热点方向.本文发现铟插层的过渡金属硫族化合物In_(x)TaSe_(2)(112体系)具有两个外尔环,以及电荷密度波(CDW)和超导电性共存的特点.在x=0.58的样品中,发现在116和77 K温度以下具有2×√3和2×2的公度CDW,这可以被电阻率、比热和扫描隧道显微镜等测量证实.角分辨光电子能谱测量发现2×2 CCDW会打开其中一个外尔环的能隙,而另一个外尔环仍然存在,且具有理论预言的"drumhead"型表面态.另外,Tc=1 K的超导电性和低温偏离s波的临界场行为表明这个材料很可能是拓扑超导体,这为探索拓扑超导电性提供了新体系.

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 In_(x)TaSe_(2)(named 112 system),a topological nodal-line semimetal in the prep seffiffinffi ce 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.