Observation of sixfold degenerate fermions in PdSb2

• DOI: 10.1103/physrevb.101.201105
• Publication Date: 2020-05-11T16:08:58Z
• Authors: Xiàn Yáng; Tyler A. Cochran; Ramakanta Chapai; Damien Tristant; Jia-Xin Yin; Ilya Belopolski; Zĭjiā Chéng; Daniel Multer; Songtian S. Zhang; Nana Shumiya; Maksim Litskevich; Yuxiao Jiang; Guoqing Chang; Qi Zhang; Ilya Vekhter; William A. Shelton; Rongying Jin; Su-Yang Xu; M. Zahid Hasan
• Keywords: Condensed Matter - Materials Science; Condensed Matter - Strongly Correlated Electrons; Condensed Matter - Mesoscale and Nanoscale Physics; Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); 0103 physical sciences; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; 01 natural sciences

Three types of fermions have been extensively studied in topological quantum materials: Dirac, Weyl, and Majorana fermions. Beyond the fundamental high energy physics, exotic are allowed condensed matter systems residing three-, six- or eightfold degenerate band crossings. Here, we use angle-resolved photoemission spectroscopy to directly visualize three-doubly-degenerate bands PdSb$_2$. The ultrahigh resolution able achieve allows for confirmation all sixfold at R point, remarkable consistency with first-principles calculations. Moreover, find that this crossing has quadratic dispersion as predicted by theory. Finally, compare previously confirmed demonstrate importance work: our study indicates a fermion beyond constraints physics.