Cho Chang-Woo, Lyu Jian, An Liheng, Han Tianyi, Lo Kwan To, Ng Cheuk Yin, Hu Jiaqi, Gao Yuxiang, Li Gaomin, Huang Mingyuan, Wang Ning, Schmalian Jörg, Lortz Rolf
Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Department of Physics, Southern University of Science and Technology, 1088 Xueyuan Road, Nanshan District, 518000 Shenzhen, Guangdong Province, China.
Phys Rev Lett. 2022 Aug 19;129(8):087002. doi: 10.1103/PhysRevLett.129.087002.
Transition metal dichalcogenides like 2H-NbSe_{2} in their two-dimensional (2D) form exhibit Ising superconductivity with the quasiparticle spins being firmly pinned in the direction perpendicular to the basal plane. This enables them to withstand exceptionally high magnetic fields beyond the Pauli limit for superconductivity. Using field-angle-resolved magnetoresistance experiments for fields rotated in the basal plane we investigate the field-angle dependence of the upper critical field (H_{c2}), which directly reflects the symmetry of the superconducting order parameter. We observe a sixfold nodal symmetry superposed on a twofold symmetry. This agrees with theoretical predictions of a nodal topological superconducting phase near H_{c2}, together with a nematic superconducting state. We demonstrate that in NbSe_{2} such unconventional superconducting states can arise from the presence of several competing superconducting channels.
二维形式的过渡金属二硫属化物，如2H-NbSe₂，表现出伊辛超导性，其准粒子自旋被牢固地锁定在垂直于基面的方向上。这使得它们能够承受超过超导泡利极限的极高磁场。通过对在基面内旋转的磁场进行场角分辨磁阻实验，我们研究了上临界场（Hc2）的场角依赖性，它直接反映了超导序参量的对称性。我们观察到六重节点对称性叠加在二重对称性之上。这与接近Hc2的节点拓扑超导相以及向列超导态的理论预测相符。我们证明，在NbSe₂中，这种非常规超导态可能源于几个相互竞争的超导通道的存在。
