Nexus fermions in topological symmorphic crystalline metals

Guoqing Chang, Su Yang Xu, Shin Ming Huang, Daniel S. Sanchez, Chuang Han Hsu, Guang Bian, Zhi Ming Yu, Ilya Belopolski, Nasser Alidoust, Hao Zheng, Tay Rong Chang, Horng Tay Jeng, Shengyuan A. Yang, Titus Neupert, Hsin Lin, M. Zahid Hasan

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Abstract

Topological metals and semimetals (TMs) have recently drawn significant interest. These materials give rise to condensed matter realizations of many important concepts in high-energy physics, leading to wide-ranging protected properties in transport and spectroscopic experiments. It has been well-established that the known TMs can be classified by the dimensionality of the topologically protected band degeneracies. While Weyl and Dirac semimetals feature zero-dimensional points, the band crossing of nodal-line semimetals forms a one-dimensional closed loop. In this paper, we identify a TM that goes beyond the above paradigms. It shows an exotic configuration of degeneracies without a well-defined dimensionality. Specifically, it consists of 0D nexus with triple-degeneracy that interconnects 1D lines with double-degeneracy. We show that, because of the novel form of band crossing, the new TM cannot be described by the established results that characterize the topology of the Dirac and Weyl nodes. Moreover, triply-degenerate nodes realize emergent fermionic quasiparticles not present in relativistic quantum field theory. We present materials candidates. Our results open the door for realizing new topological phenomena and fermions including transport anomalies and spectroscopic responses in metallic crystals with nontrivial topology beyond the Weyl/Dirac paradigm.

Original languageEnglish (US)
Article number1688
JournalScientific reports
Volume7
Issue number1
DOIs
StatePublished - Dec 1 2017

All Science Journal Classification (ASJC) codes

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    Chang, G., Xu, S. Y., Huang, S. M., Sanchez, D. S., Hsu, C. H., Bian, G., Yu, Z. M., Belopolski, I., Alidoust, N., Zheng, H., Chang, T. R., Jeng, H. T., Yang, S. A., Neupert, T., Lin, H., & Hasan, M. Z. (2017). Nexus fermions in topological symmorphic crystalline metals. Scientific reports, 7(1), [1688]. https://doi.org/10.1038/s41598-017-01523-8