Observation of sixfold degenerate fermions in PdS b2

Xiàn Yáng, Tyler A. Cochran, Ramakanta Chapai, Damien Tristant, Jia Xin Yin, Ilya Belopolski, Zajiā 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

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Three types of fermions have been extensively studied in topological quantum materials: Dirac, Weyl, and Majorana fermions. Beyond the fundamental fermions in high energy physics, exotic fermions are allowed in condensed matter systems residing in three-, six-or eightfold degenerate band crossings. Here, we use angle-resolved photoemission spectroscopy to directly visualize three-doubly-degenerate bands in PdSb2. The ultrahigh energy resolution we are able to achieve allows for the confirmation of all the sixfold degenerate bands at the R point, in remarkable consistency with first-principles calculations. Moreover, we find that this sixfold degenerate crossing has quadratic dispersion as predicted by theory. Finally, we compare sixfold degenerate fermions with previously confirmed fermions to demonstrate the importance of this work: our study indicates a topological fermion beyond the constraints of high energy physics.

Original languageEnglish (US)
Article number201105
JournalPhysical Review B
Issue number20
StatePublished - May 15 2020

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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