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Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

DOI: 10.1126/sciadv.1603266 DOI Help

Authors: Su-Yang Xu (Princeton University) , Nasser Alidoust (Princeton University) , Guoqing Chang (National University of Singapore) , Hong Lu (Peking University) , Bahadur Singh (National University of Singapore) , Ilya Belopolski (Princeton University) , Daniel S. Sanchez (Princeton University) , Xiao Zhang (Peking University) , Guang Bian (Princeton University) , Hao Zheng (Princeton University) , Marious-Adrian Husanu (Swiss Light Source; National Institute of Materials Physics) , Yi Bian (Peking University) , Shin-Ming Huang (National University of Singapore; Sun Yat-Sen University) , Chuang-Han Hsu (National University of Singapore) , Tay-Rong Chang (National Tsing Hua University; National Cheng Kung University) , Horng-Tay Jeng (Princeton University) , Arun Bansil (Northeastern University) , Titus Neupert (University of Zurich) , Vladimir N. Strocov (Swiss Light Source) , Hsin Lin (National University of Singapore) , Shuang Jia (Peking University; Collaborative Innovation Center of Quantum Matter, Beijing) , M. Zahid Hasan (Princeton University)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Science Advances , VOL 3

State: Published (Approved)
Published: June 2017

Open Access Open Access

Abstract: In quantum field theory, Weyl fermions are relativistic particles that travel at the speed of light and strictly obey the celebrated Lorentz symmetry. Their low-energy condensed matter analogs are Weyl semimetals, which are conductors whose electronic excitations mimic the Weyl fermion equation of motion. Although the traditional (type I) emergent Weyl fermions observed in TaAs still approximately respect Lorentz symmetry, recently, the so-called type II Weyl semimetal has been proposed, where the emergent Weyl quasiparticles break the Lorentz symmetry so strongly that they cannot be smoothly connected to Lorentz symmetric Weyl particles. Despite some evidence of nontrivial surface states, the direct observation of the type II bulk Weyl fermions remains elusive. We present the direct observation of the type II Weyl fermions in crystalline solid lanthanum aluminum germanide (LaAlGe) based on our photoemission data alone, without reliance on band structure calculations. Moreover, our systematic data agree with the theoretical calculations, providing further support on our experimental results.

Journal Keywords: Topological Materials; Weyl semimetals

Subject Areas: Physics, Materials

Instruments: I05-ARPES

Other Facilities: ALS; Stanford Synchrotron Radiation Lightsource; Swiss Light Source

Added On: 06/06/2017 14:20


Discipline Tags:

Quantum Materials Physics Hard condensed matter - structures Materials Science

Technical Tags:

Spectroscopy Angle Resolved Photoemission Spectroscopy (ARPES)