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Title: Discovery of Lorentz-violating type II Weyl fermions in LaAlGe

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. Furthermore, our systematic data agree with the theoretical calculations, providing further support on our experimental results.

Authors:
 [1];  [2]; ORCiD logo [3];  [4]; ORCiD logo [3];  [1];  [1];  [4];  [5];  [1]; ORCiD logo [6];  [4]; ORCiD logo [7]; ORCiD logo [3]; ORCiD logo [8];  [9];  [10];  [11];  [12]; ORCiD logo [3] more »;  [13];  [1] « less
  1. Princeton Univ., Princeton, NJ (United States)
  2. Princeton Univ., Princeton, NJ (United States); Rigetti & Co Inc., Berkeley, CA (United States)
  3. National Univ. of Singapore (Singapore)
  4. Peking Univ., Beijing (China)
  5. Princeton Univ., Princeton, NJ (United States); Univ. of Missouri, Columbia, MO (United States)
  6. Paul Scherrer Inst. (PSI), Villigen (Switzerland); National Institute of Materials Physics, Magurele (Romania)
  7. National Univ. of Singapore (Singapore); National Sun Yat-Sen Univ., Kaohsiung (Taiwan)
  8. National Tsing Hua Univ., Hsinchu (Taiwan); National Cheng Kung Univ., Tainan (Taiwan)
  9. National Tsing Hua Univ., Hsinchu (Taiwan); Academia Sinica, Taipei (Taiwan)
  10. Northeastern Univ., Boston, MA (United States)
  11. Univ. of Zurich, Winterthurerstrasse (Switzerland)
  12. Paul Scherrer Inst. (PSI), Villigen (Switzerland)
  13. Peking Univ., Beijing (China); Collaborative Innovation Center of Quantum Matter, Beijing (China)
Publication Date:
Research Org.:
Northeastern Univ., Boston, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1473922
Grant/Contract Number:  
FG02-07ER46352; FG02-05ER46200; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 3; Journal Issue: 6; Journal ID: ISSN 2375-2548
Publisher:
AAAS
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Topological Materials; Weyl semimetals

Citation Formats

Xu, Su -Yang, Alidoust, Nasser, Chang, Guoqing, Lu, Hong, Singh, Bahadur, Belopolski, Ilya, Sanchez, Daniel S., Zhang, Xiao, Bian, Guang, Zheng, Hao, Husanu, Marious -Adrian, Bian, Yi, Huang, Shin -Ming, Hsu, Chuang -Han, Chang, Tay -Rong, Jeng, Horng -Tay, Bansil, Arun, Neupert, Titus, Strocov, Vladimir N., Lin, Hsin, Jia, Shuang, and Hasan, M. Zahid. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe. United States: N. p., 2017. Web. doi:10.1126/sciadv.1603266.
Xu, Su -Yang, Alidoust, Nasser, Chang, Guoqing, Lu, Hong, Singh, Bahadur, Belopolski, Ilya, Sanchez, Daniel S., Zhang, Xiao, Bian, Guang, Zheng, Hao, Husanu, Marious -Adrian, Bian, Yi, Huang, Shin -Ming, Hsu, Chuang -Han, Chang, Tay -Rong, Jeng, Horng -Tay, Bansil, Arun, Neupert, Titus, Strocov, Vladimir N., Lin, Hsin, Jia, Shuang, & Hasan, M. Zahid. Discovery of Lorentz-violating type II Weyl fermions in LaAlGe. United States. doi:10.1126/sciadv.1603266.
Xu, Su -Yang, Alidoust, Nasser, Chang, Guoqing, Lu, Hong, Singh, Bahadur, Belopolski, Ilya, Sanchez, Daniel S., Zhang, Xiao, Bian, Guang, Zheng, Hao, Husanu, Marious -Adrian, Bian, Yi, Huang, Shin -Ming, Hsu, Chuang -Han, Chang, Tay -Rong, Jeng, Horng -Tay, Bansil, Arun, Neupert, Titus, Strocov, Vladimir N., Lin, Hsin, Jia, Shuang, and Hasan, M. Zahid. Fri . "Discovery of Lorentz-violating type II Weyl fermions in LaAlGe". United States. doi:10.1126/sciadv.1603266. https://www.osti.gov/servlets/purl/1473922.
@article{osti_1473922,
title = {Discovery of Lorentz-violating type II Weyl fermions in LaAlGe},
author = {Xu, Su -Yang and Alidoust, Nasser and Chang, Guoqing and Lu, Hong and Singh, Bahadur and Belopolski, Ilya and Sanchez, Daniel S. and Zhang, Xiao and Bian, Guang and Zheng, Hao and Husanu, Marious -Adrian and Bian, Yi and Huang, Shin -Ming and Hsu, Chuang -Han and Chang, Tay -Rong and Jeng, Horng -Tay and Bansil, Arun and Neupert, Titus and Strocov, Vladimir N. and Lin, Hsin and Jia, Shuang and Hasan, M. Zahid},
abstractNote = {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. Furthermore, our systematic data agree with the theoretical calculations, providing further support on our experimental results.},
doi = {10.1126/sciadv.1603266},
journal = {Science Advances},
number = 6,
volume = 3,
place = {United States},
year = {2017},
month = {6}
}

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