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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); Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
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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Figures / Tables:

Fig. 1 Fig. 1: Topology and BZ symmetry of LaAlGe. (A) Body-centered tetragonal structure of LaAlGe, with space group I41md (109). The structure consists of stacks of La, Al, and Ge layers, and along the (001) direction, each layer consists of only one type of element. (B) The bulk and (001) surfacemore » BZ. (C) First-principles band structure calculations along high-symmetry directions without spin-orbit coupling (SOC). (D) Momentum space configuration of the four nodal lines (two on the kx = 0 and two on the ky = 0 mirror planes) denoted by the rings, as well as the four spinless pairs of Weyl nodes denoted as W3 on the kz = 0 plane, in the absence of SOC. Blue and red colors indicate positive and negative chiralities, respectively. (E) Configuration of the 40 Weyl nodes in the bulk BZ created upon the inclusion of SOC. The nodal lines are gapped out by SOC, and 24 Weyl nodes emerge in the vicinity of the nodal lines. In addition, each spinless W3 Weyl node splits into two spinful Weyl nodes of the same chirality, which we denote as W3′ and W3″. Hence, the eight W3 without SOC evolve into eight W3′ and eight W3′′ Weyl nodes with SOC. Therefore, in total, there are 40 Weyl nodes. For the 24 Weyl nodes that emerge from the gapping of the nodal line, we denote the 8 Weyl nodes that are near the boundaries of kz = 0 plane as W1 and the other 16 that are away from the $k$z = 0 plane as W2. The W3′ and W3′′ are also on the kz = 0 plane, but they are near the diagonal lines. (F) Projection of the Weyl nodes on the (001) surface BZ in one quadrant. (G) Schematics comparing the three types of Weyl nodes appearing upon the inclusion of SOC. The W2 nodes are type II Weyl nodes, whereas the W1, W3′, and W3′′ nodes are type I. W2 Weyl nodes are located almost exactly at the Fermi level, whereas W1, W3′, and W3′′ Weyl nodes are about 60, 110, and 130 meV above the Fermi level, respectively. (H) Core level measurement of the studied samples, which clearly shows the expected La, Al, and Ge peaks. a.u., arbitrary units.« less

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Works referenced in this record:

Generalized Gradient Approximation Made Simple
journal, October 1996

  • Perdew, John P.; Burke, Kieron; Ernzerhof, Matthias
  • Physical Review Letters, Vol. 77, Issue 18, p. 3865-3868
  • DOI: 10.1103/PhysRevLett.77.3865

Spectroscopic evidence for a type II Weyl semimetallic state in MoTe2
journal, July 2016

  • Huang, Lunan; McCormick, Timothy M.; Ochi, Masayuki
  • Nature Materials, Vol. 15, Issue 11
  • DOI: 10.1038/nmat4685

Predicted Unusual Magnetoresponse in Type-II Weyl Semimetals
journal, August 2016


Observation of Fermi arc and its connection with bulk states in the candidate type-II Weyl semimetal WTe 2
journal, December 2016


Robust Type-II Weyl Semimetal Phase in Transition Metal Diphosphides X P 2 ( X = Mo , W)
journal, August 2016


Type-II Weyl semimetals
journal, November 2015

  • Soluyanov, Alexey A.; Gresch, Dominik; Wang, Zhijun
  • Nature, Vol. 527, Issue 7579
  • DOI: 10.1038/nature15768

Type-II Weyl cone transitions in driven semimetals
journal, September 2016


Structured Weyl Points in Spin-Orbit Coupled Fermionic Superfluids
journal, December 2015


Soft-X-ray ARPES at the Swiss Light Source: From 3D Materials to Buried Interfaces and Impurities
journal, March 2014


Consequences of a condensed matter realization of Lorentz-violating QED in Weyl semi-metals
journal, August 2012


Metal-metal vs tellurium-tellurium bonding in WTe2 and its ternary variants TaIrTe4 and NbIrTe4
journal, November 1992

  • Mar, Arthur; Jobic, Stephane; Ibers, James A.
  • Journal of the American Chemical Society, Vol. 114, Issue 23
  • DOI: 10.1021/ja00049a029

Classification of stable three-dimensional Dirac semimetals with nontrivial topology
journal, September 2014

  • Yang, Bohm-Jung; Nagaosa, Naoto
  • Nature Communications, Vol. 5, Issue 1
  • DOI: 10.1038/ncomms5898

Elektron und Gravitation. I
journal, May 1929


A strongly robust type II Weyl fermion semimetal state in Ta 3 S 2
journal, June 2016

  • Chang, Guoqing; Xu, Su-Yang; Sanchez, Daniel S.
  • Science Advances, Vol. 2, Issue 6
  • DOI: 10.1126/sciadv.1600295

Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
journal, October 1996


Experimental observation of Weyl points
journal, July 2015


From ultrasoft pseudopotentials to the projector augmented-wave method
journal, January 1999


Topology and Interactions in a Frustrated Slab: Tuning from Weyl Semimetals to C > 1 Fractional Chern Insulators
journal, January 2015


Weyl Semimetal in a Topological Insulator Multilayer
journal, September 2011


Magnetic Breakdown and Klein Tunneling in a Type-II Weyl Semimetal
journal, June 2016


Experimental observation of topological Fermi arcs in type-II Weyl semimetal MoTe2
journal, September 2016

  • Deng, Ke; Wan, Guoliang; Deng, Peng
  • Nature Physics, Vol. 12, Issue 12
  • DOI: 10.1038/nphys3871

Maximally localized generalized Wannier functions for composite energy bands
journal, November 1997


MoTe 2 : A Type-II Weyl Topological Metal
journal, July 2016


Signatures of the Adler–Bell–Jackiw chiral anomaly in a Weyl fermion semimetal
journal, February 2016

  • Zhang, Cheng-Long; Xu, Su-Yang; Belopolski, Ilya
  • Nature Communications, Vol. 7, Issue 1
  • DOI: 10.1038/ncomms10735

Discovery of a Weyl fermion semimetal and topological Fermi arcs
journal, July 2015


Prediction of an arc-tunable Weyl Fermion metallic state in MoxW1−xTe2
journal, February 2016

  • Chang, Tay-Rong; Xu, Su-Yang; Chang, Guoqing
  • Nature Communications, Vol. 7, Issue 1
  • DOI: 10.1038/ncomms10639

Inhomogeneous Electron Gas
journal, November 1964


Quantum oscillations from surface Fermi arcs in Weyl and Dirac semimetals
journal, October 2014

  • Potter, Andrew C.; Kimchi, Itamar; Vishwanath, Ashvin
  • Nature Communications, Vol. 5, Issue 1
  • DOI: 10.1038/ncomms6161

Ternary rare-earth alumo-silicides—single-crystal growth from Al flux, structural and physical properties
journal, June 2005

  • Bobev, Svilen; Tobash, Paul H.; Fritsch, Veronika
  • Journal of Solid State Chemistry, Vol. 178, Issue 6
  • DOI: 10.1016/j.jssc.2005.04.021

Experimental Discovery of Weyl Semimetal TaAs
journal, July 2015


Data tables for Lorentz and C P T violation
journal, March 2011


The Adler-Bell-Jackiw anomaly and Weyl fermions in a crystal
journal, November 1983


Field-Selective Anomaly and Chiral Mode Reversal in Type-II Weyl Materials
journal, August 2016


Magnetic-Field-Induced Relativistic Properties in Type-I and Type-II Weyl Semimetals
journal, August 2016


Accidental Degeneracy in the Energy Bands of Crystals
journal, August 1937


Prediction of Weyl semimetal in orthorhombic MoTe 2
journal, October 2015


Soft-X-ray ARPES facility at the ADRESS beamline of the SLS: concepts, technical realisation and scientific applications
journal, November 2013


Observation of Fermi arcs in the type-II Weyl semimetal candidate WTe 2
journal, September 2016


Intrinsic anomalous Hall effect in type-II Weyl semimetals
journal, June 2016


Modern Tests of Lorentz Invariance
journal, September 2005


Signature of type-II Weyl semimetal phase in MoTe2
journal, January 2017

  • Jiang, J.; Liu, Z. K.; Sun, Y.
  • Nature Communications, Vol. 8, Issue 1
  • DOI: 10.1038/ncomms13973

TaIrTe 4 : A ternary type-II Weyl semimetal
journal, May 2016


Topological semimetal and Fermi-arc surface states in the electronic structure of pyrochlore iridates
journal, May 2011


    Works referencing / citing this record:

    Nonsaturating Magnetoresistance and Nontrivial Band Topology of Type‐II Weyl Semimetal NbIrTe 4
    journal, July 2019

    • Zhou, Wei; Li, Bin; Xu, Chun Qiang
    • Advanced Electronic Materials, Vol. 5, Issue 8
    • DOI: 10.1002/aelm.201900250

    Nonsaturating Magnetoresistance and Nontrivial Band Topology of Type‐II Weyl Semimetal NbIrTe 4
    journal, July 2019

    • Zhou, Wei; Li, Bin; Xu, Chun Qiang
    • Advanced Electronic Materials, Vol. 5, Issue 8
    • DOI: 10.1002/aelm.201900250

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