Direct observation of sixfold exotic fermions in the pyrite-structured topological semimetal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>PdSb</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>
Zhenyu Sun, Chenqiang Hua, Xiaolei Liu, Z. T. Liu, M. Ye, Shan Qiao, Zhonghao Liu, J. S. Liu, Yanfeng Guo, Yunhao Lu, Dawei Shen
Abstract
Rather than Poincar\`e symmetry, it is the invariance under crystal symmetry of space groups that constrains fermions in solids, and thus there might exist some exotic fermions beyond elementary particles in high-energy physics. Here, the authors verify the existence of the long-sought-after sixfold fermions in pyrite PdSb${}_{2}$ by means of high-resolution ARPES and first-principles calculations. They show that this sixfold degeneracy is a heretofore unknown single fermion node carrying zero Chern number, quite unlike the previously reported sixfold double spin-1 chiral fermions.
Topics & Concepts
FermionDegeneracy (biology)PhysicsSymmetry (geometry)SemimetalTheoretical physicsTopology (electrical circuits)Quantum mechanicsGeometryBioinformaticsMathematicsCombinatoricsBiologyBand gapTopological Materials and PhenomenaGraphene research and applicationsAdvanced Condensed Matter Physics