Welcome to the Hasan Group/Lab website!
Our lab is focused on the search and discovery of novel quantum phases of matter. Currently, we grow and control properties of quantum materials, perform firstprinciple theoretical calculations/predictions and develop advanced spectroscopic techniques and related tools that provide new insights into the emergent behavior of matter. We invite you to visit our labs (Laboratory for Topo. Quantum Matter and Spectroscopy: B7B2B9B60 Jadwin Hall) in the dept of physics at Princeton. Prof. Hasan is also affiliated with Lawrence Berkeley National Laboratory in California.
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Lab Theme: QFT, Topology & Emergence in the Condensed Matter Universe Probe, Predict and Control Topological Structure of Quantum Matter New Topological States of Matter & New Emergent Particles Reading List (click here) U.S. Dept of Energy support (DOE physicists at work) Topo.Insulators in 2007, KITP Talk Proc.(2007) PNAS Front Matter homepage (September, 2016): Topological Insulators Proc. of National Academy of Sciences USA PhysicsWorld (U.K.) homepage (August, 2016): Topo. Insulators (100s Science Series) Physics Today: "Search & Discovery" News on Topological Insulators PhysicsWorld (February, 2011); Physics Today (January, 2010) Physics Today (U.S.A.) New funding for Quantum Systems (2013) ; IEEE Spectrum (2015) A vast majority of our experimental works are based on our own theoretical predictions of topological materials (link) Massless Yet Real (2015); PhysicsWorld (March, 2016) PhysicsWorld News (July, 2015) Weyl fermion semimetals & Fermi arcs PhysicsWorld (March, 2016) Weyl fermion semimetals & Topo. Nodal Fermion Semimetals Discovery of Weyl Fermions, Topological Fermi Arcs and Topological NodalLine States of Matter (Key Developments in Physics: 2Physics, 2015) PhysicsWorld multimedia interview: "What is a Topological Metal? (2016) New Topological Phases of Matter: Platform for emergent Dirac, Majorana & Weyl fermions (2016) PhysicsWorld (2016) Recent Publications : (Topological Semimetals) Weyl semimetals, Fermi arcs and chiral anomaly  
Cover Image Weyl semimetals, Fermi arcs and chiral anomaly S. Jia, S.Y. Xu, M. Z. Hasan " Physicists have discovered a new topological phase of matter, the Weyl semimetal, whose surface features a nonclosed Fermi surface whereas the lowenergy quasiparticles in the bulk emerge as Weyl fermions. A brief review of these developments and perspectives on the next steps forward are presented." Nature Materials 15, 11401144 (2016) (Cover Story) Focus Issue on Topological Semimetals 

Signatures of the AdlerBellJackiw chiral anomaly in a Weyl semimetal C. Zhang, S.Y. Xu, I. Belopolski, Z. Yuan, Z. Lin, B. Tong, N. Alidoust, C.C. Lee, S.M. Huang, H. Lin, M. Neupane, D. S. Sanchez, H. Zheng, G. Bian, J. Wang, C. Zhang, T. Neupert, M. Z. Hasan, S. Jia Nature Communications 7:10735 (2016) 

Also see, Weyl semimetals, Fermi arcs and chiral anomaly (minireview) Nature Materials 15, 11401144 (2016) (Cover Story)  
A strongly robust type II topological Weyl fermion semimetal state in Ta3S2 Guoqing Chang, SuYang Xu, Daniel S. Sanchez, ShinMing Huang, ChiCheng Lee, TayRong Chang, Guang Bian, Hao Zheng, Ilya Belopolski, Nasser Alidoust, HorngTay Jeng, Arun Bansil, Hsin Lin, and M. Zahid Hasan Science Adv. e1600295 (2016) 

Spin polarization and texture of the Fermi arcs in the Weyl Fermion semimetal TaAs S.Y. Xu, I. Belopolski, D. S. Sanchez, M. Neupane, G. Chang, K. Yaji, Z. Yuan, C. Zhang, K. Kuroda, G. Bian, C. Guo, H. Lu, Y. Feng, T.R. Chang, N. Alidoust, H. Zheng, C.C. Lee, S.M. Huang, C.H. Hsu, HorngTay Jeng, A. Bansil, A. Alexandradinata, T. Neupert, T. Kondo, S. Shin, H. Lin, S. Jia, M Z. Hasan Phys. Rev. Lett. 116, 096801 (2016) 

Discovery of Weyl fermion semimetals named a 'breakthrough of the year' by Physics World
PhysicsWorld News: "Weyl fermions are spotted at long last" News at Lawrence Berkeley National Laboratory (LBNL), MIT physics news Physics Highlights of the Year 2015 (Physics  American Physical Society) 

Atomic Scale Visualization of Quantum Interference on a Weyl Semimetal Surface by Scanning Tunneling Microscopy/Spectroscopy H. Zheng, S.Y. Xu, G. Bian, C. Guo, G. Chang, D. S. Sanchez, I. Belopolski, C.C. Lee, S.M. Huang, X. Zhang, R. Sankar, N. Alidoust, T.R. Chang, F. Wu, T. Neupert, F. Chou, H.T. Jeng, N. Yao, A. Bansil, S. Jia, H. Lin, M. Z. Hasan ACS Nano 10, 1378 (2016, submitted Oct 2015) 

New funding for quantum systems 

Engineering electronic structure of a 2D topological insulator Bi(111) bilayer on Sb nanofilms by quantum confinement effect G. Bian, Z. F. Wang, X. Wang, C. Xu, S.Y. Xu, T. Miller, M. Z. Hasan, F. Liu, and T.C. Chiang ACS Nano 10, 3859 (2016) 

Signatures of Fermi Arcs in the Quasiparticle Interferences of the Weyl Semimetals TaAs and NbP G. Chang, S.Y. Xu, H. Zheng et al., Phys. Rev. Lett. 116, 066601 (2016) 

New type of Weyl semimetal with quadratic double Weyl fermions in SrSi2 S.M. Huang, S.Y. Xu, I. Belopolski et al., PNAS 113, 1180 (2015) 

Criteria for Directly Detecting Topological Fermi Arcs in Weyl Semimetals I. Belopolski, S.Y. Xu, D. S. Sanchez et al. Phys. Rev. Lett. 116, 066802 (2016) 

Prediction of an arctunable Weyl Fermion metallic state in Mo_{x}W_{1x}Te_{2} T.R. Chang, S.Y. Xu, G. Chang et al. Nature Commun. 7:10639 (2016) 

Discovery of a new type of Weyl semimetal state I. Belopolski et al., Nature Commun. (2016) 

Unconventional transformation of spin Dirac phase across a topological quantum phase transition S.Y. Xu, M. Neupane, I. Belopolski et al. Nature Commun. 6:6870 (2015) 

Topological Nodalline Fermions and Semimetals 

Topological NodalLine Fermions in SpinOrbit Metal PbTaSe_{2} G. Bian, T.R. Chang, R. Sankar, S.Y. Xu, H. Zheng, T. Neupert, C.K. Chiu, S.M. Huang, G. Chang, I. Belopolski, D. S. Sanchez, M. Neupane, N. Alidoust, C. Liu, B. Wang, H.T. Jeng, A. Bansil, F. Chou, H. Lin, and M. Z. Hasan Nature Commun. 7:10556 (2016, submitted Nov 2015) 



Roomtemperature magnetic topological Weyl fermion and nodal line semimetal states in halfmetallic Heusler Co2TiX (X=Si, Ge, or Sn). Guoqing Chang, SuYang Xu, Hao Zheng, Bahadur Singh, ChuangHan Hsu, Guang Bian, Nasser Alidoust, Ilya Belopolski, Daniel S. Sanchez, Songtian Zhang, Hsin Lin & M. Zahid Hasan Scientific Reports 6, 38839 (2016). 

PumpProbe Ultrafast Spectroscopy 

Gigantic surface lifetime of an intrinsic topological insulator revealed via timeresolved (pumpprobe) ARPES M. Neupane, S.Y. Xu, Y. Ishida, S. Jia, B. M. Fregoso, C. Liu, I. Belopolski, G. Bian, N. Alidoust, T. Durakiewicz, V. Galitski, S. Shin, R. J. Cava, and M. Z. Hasan Phys. Rev. Lett. 115, 116801 (2015) 



Discovery of Weyl Fermion Semimetals: TaAs, NbAs, NbP, TaP, SrSi_{2}, Ta3S2, LaAlGe 

Topological electronic structure and Weyl semimetal in the TlBiSe2 class of semiconductors. B. Singh, A.h Sharma, H. Lin, M. Z. Hasan, R. Prasad, and A. Bansil Physical Review B 86, 115208 (2012) Theoretical Prediction: A Weyl Fermion semimetal with surface Fermi arcs in the transition metal monopnictide TaAs class S.M. Huang, S.Y. Xu, I. Belopolski, C.C. Lee, G. Chang, B. Wang, N. Alidoust, G. Bian, M. Neupane, C. Zhang, S. Jia, A. Bansil, H. Lin, M. Z. Hasan Nature Commun. 6:7373 (2015) (submitted Nov 2014) Also see: Phys. Rev. X 5, 011029 (2015) (submitted Jan 2015) Experimental Discovery: Discovery of a Weyl Fermion semimetal and topological Fermi arcs S.Y. Xu, I. Belopolski, N. Alidoust, M. Neupane, G. Bian, C. Zhang, R. Sankar, G. Chang, Z. Yuan, C.C. Lee, S.M. Huang, H. Zheng, J. Ma, D. S. Sanchez, B. Wang, A. Bansil, F. Chou, P. P. Shibayev, H. Lin, S. Jia, and M. Z. Hasan Science 349, 613 (2015) (submitted Feb. 2015) PhysicsWorld News: "Weyl fermions are spotted at long last" APSPhysics (American Physical Society): "Weyl Fermions" Science News: "Elusive particle shows up in semimetal" Nature Materials News: "Weyl fermions: Massless yet real" Nature Physics News: "After a Weyl" ChemistryWorld News: "Elusive fermion found at long last" Physics (American Physical Society): "Where the Weyl Things Are" Discovery of a Weyl Fermion state with Fermi arcs in niobium arsenide S.Y. Xu, N. Alidoust, I. Belopolski, Z. Yuan, G. Bian, T.R. Chang, H. Zheng, V. Strocov, D. S. Sanchez, G. Chang, C. Zhang, D. Mou, Y. Wu, L. Huang, C.C. Lee, S.M. Huang, B. Wang, A. Bansil, H.T. Jeng, T. Neupert, A. Kaminski, H. Lin, S. Jia, and M. Z. Hasan Nature Physics 11, 748 (2015) NaturePhysics: "Discovery of a Weyl Fermion state" Nature Physics News: "After a Weyl" Experimental discovery of a topological Weyl semimetal state in TaP S.Y. Xu, I. Belopolski, D. S. Sanchez, C. Guo, G. Chang, C. Zhang, G. Bian, Z. Yuan, H. Lu, Yi. Feng, T.R. Chang, P. P. Shibayev, M. L. Prokopovych, N. Alidoust, H. Zheng, C.C. Lee, S.M. Huang, R. Sankar, F. Chou, C.H. Hsu, H.T. Jeng, A, Bansil, T. Neupert, V. N. Strocov, H. Lin, S. Jia, M. Z. Hasan Science Advances 1, 1501092 (2015) Fermi arc topology and interconnectivity in Weyl fermion semimetals TaAs, TaP, NbAs, and NbP C.C. Lee, S.Y. Xu, S.M. Huang, D. S. Sanchez, I. Belopolski, G. Chang, G. Bian, N. Alidoust, H. Zheng, M. Neupane,B. Wang, A. Bansil, M. Z. Hasan, and H. Lin Phys. Rev. B 92, 235104 (2015) Signatures of Fermi Arcs in the Quasiparticle Interferences of the Weyl Semimetals TaAs and NbP G. Chang, S.Y. Xu, H. Zheng, C.C. Lee, S.M. Huang, I. Belopolski, D. S. Sanchez, G. Bian, N. Alidoust, T.R. Chang, C.H. Hsu, H.T. Jeng, A. Bansil, H. Lin, M. Z. Hasan Phys. Rev. Lett. 116, 066601 (2016) Criteria for Directly Detecting Topological Fermi Arcs in Weyl Semimetals I. Belopolski, S.Y. Xu, D. S. Sanchez, G. Chang, C. Guo, M. Neupane, H. Zheng, C.C. Lee, S.M. Huang, G. Bian, N. Alidoust, T.R. Chang, B. Wang, X. Zhang, A. Bansil, H.T. Jeng, H. Lin, S. Jia, M. Z. Hasan Phys. Rev. Lett. 116, 066802 (2016) New type of Weyl semimetal with quadratic double Weyl fermions S.M. Huang, S.Y. Xu, I. Belopolski, C.C. Lee, G. Chang, B. Wang, N. Alidoust, M. Neupane, H. Zheng, D. Sanchez, A. Bansil, G. Bian, H. Lin, and M. Z. Hasan Proc. of National Academy of Sciences USA 113, 1180 (2015) Prediction of an arctunable Weyl Fermion metallic state in Mo_{x}W_{1x}Te_{2} T.R. Chang, S.Y. Xu, G. Chang, C.C. Lee, S.M. Huang, B. Wang, G. Bian, H. Zheng, D. S. Sanchez, I. Belopolski, N. Alidoust, M. Neupane, A. Bansil, H.T. Jeng, H. Lin, M. Zahid Hasan Nature Commun. 7:10639 (2016) Signatures of the AdlerBellJackiw chiral anomaly in a Weyl semimetal C. Zhang, S.Y. Xu, I. Belopolski, Z. Yuan, Z. Lin, B. Tong, N. Alidoust, C.C. Lee, S.M. Huang, H. Lin, M. Neupane, D. S. Sanchez, H. Zheng, G. Bian, J. Wang, C. Zhang, T. Neupert, M. Z. Hasan, S. Jia Nature Commun. 7:10735 (2016) Spin polarization and texture of the Fermi arcs in the Weyl Fermion semimetal TaAs S.Y. Xu, I. Belopolski, D. S. Sanchez, M. Neupane, G. Chang, K. Yaji, Z. Yuan, C. Zhang, K. Kuroda, G. Bian, C. Guo, H. Lu, Y. Feng, T.R. Chang, N. Alidoust, H. Zheng, C.C. Lee, S.M. Huang, C.H. Hsu, HorngTay Jeng, A. Bansil, A. Alexandradinata, T. Neupert, T. Kondo, S. Shin, H. Lin, S. Jia, M Z. Hasan Phys. Rev. Lett. 116, 096801 (2016) Unoccupied electronic structure and signatures of topological Fermi arcs in the Weyl semimetal candidate Mo_{x}W_{1x}Te_{2} I. Belopolski, S.Y. Xu, Y. Ishida, X. Pan, P. Yu, D. S. Sanchez, M. Neupane, N. Alidoust, G. Chang, T.R. Chang, Y. Wu, G. Bian, H. Zheng, S.M. Huang, C.C. Lee, D. Mou, L. Huang, Y. Song, B. Wang, G. Wang, Y.W. Yeh, N. Yao, J. Rault, P. Lefevre, F. Bertran, H.T. Jeng, T. Kondo, A. Kaminski, H. Lin, Z. Liu, F. Song, S. Shin, M. Z. Hasan Phys. Rev. B (2016) Observation of Topological Nodal Fermion Semimetal Phase in ZrSiS M. Neupane, I. Belopolski, M. M. Hosen, D. S. Sanchez, R. Sankar, M. Szlawska, S.Y. Xu, K. Dimitri, N. Dhakal, P. Maldonado, P. M. Oppeneer, D. Kaczorowski, F. Chou, M. Z. Hasan, T. Durakiewicz Phys. Rev. B (2016) A strongly robust typeII Weyl fermion semimetal state in Ta3S2 G. Chang, S.Y. Xu, D. S. Sanchez, S.M. Huang, C.C. Lee, T.R. Chang, H. Zheng, G. Bian, I. Belopolski, N. Alidoust, H.T. Jeng, A. Bansil, H. Lin, M. Z. Hasan Science Advances (2016) Magnetic and noncentrosymmetric Weyl fermion semimetals in the RAlX family of compounds (R=rare earth, Al=aluminium, X=Si, Ge) G. Chang, B. Singh, S.Y. Xu, G. Bian, S.M. Huang, C.H. Hsu, I. Belopolski, N. Alidoust, D. S. Sanchez, H. Zheng, H. Lu, X. Zhang, Y. Bian, T.R. Chang, H.T. Jeng, A. Bansil, H. Hsu, S.g Jia, T.s Neupert, H. Lin, M. Z. Hasan arXiv:1604.02124 Discovery of Lorentzviolating Weyl fermion semimetal state in LaAlGe materials S.Y. Xu, N. Alidoust, G. Chang, H. Lu, B. Singh, I. Belopolski, D. Sanchez, X. Zhang, G. Bian, H. Zheng, M.A. Husanu, Y. Bian, S.M. Huang, C.H. Hsu, T.R. Chang, H.T. Jeng, A. Bansil, V. N. Strocov, H. Lin, S. Jia, M. Z. Hasan arXiv:1603.07318 Discovery of a new type of topological Weyl fermion semimetal state I. Belopolski, D. S. Sanchez et.al., Nature Commun. 7, 13643 (2016) Phase Transitions in Weyl Semimetal Tantalum Monophosphide C. Zhang, Z. Lin, C. Guo, S.Y. Xu, C.C. Lee, H. Lu, S.M. Huang, G. Chang, C.H. Hsu, H. Lin, L. Li, C. Zhang, T. Neupert, M. Z. Hasan, J, Wang, S. Jia arXiv:1507.06301 (2015) Roomtemperature magnetic topological Weyl fermion and nodal line semimetal states in halfmetallic Heusler Co2TiX (X=Si, Ge, or Sn) G. Chang, S.Y. Xu, H. Zheng, B. Singh, C.H. Hsu, I. Belopolski, D. S. Sanchez, G. Bian, N. Alidoust, H. Lin, M. Z. Hasan Scientific Reports 6, 38839 (2016) 

Topological Weyl Semimetal and Topological Fermi Arcs  
Discovery of a Weyl Fermion semimetal and topological Fermi arcs. Published in S.Y. Xu, I. Belopolski, N. Alidoust, et al., Science 349, 613 (2015). 

A Weyl Fermion semimetal with surface Fermi arcs in the transition metal monopnictide TaAs class. Published in S.M. Huang, S.Y. Xu, I. Belopolski, et al., Nature Commun. 6:7373 (2015). 

Discovery of a Weyl fermion state with Fermi arcs in niobium arsenide. Published in S.Y. Xu, N. Alidoust, I. Belopolski, et al., Nature Physics 11, 748 (2015). 

Experimental discovery of a topological Weyl semimetal state in TaP. Published in S.Y. Xu, I. Belopolski, D. S. Sanchezet al., Science Advances 1, 1501092 (2015). 

Topological Semimetal (Double Weyl Semimetal) 

Observation of Fermi Arc Surface States in a Topological Metal. Published in S.Y. Xu, C. Liu, S. Kushwaha, et al., Science 347, 294 (2015). 

2D Topological Superconductor based on Topological Insulators 

Spin and angle resolved photoemission (spinARPES) measurements on Bi_{2}Se_{3}/NbSe_{2} heterostructure demonstrate topological superconductivity and helical Cooper pairing via proximity effect. Published in S.Y. Xu, N. Alidoust, I. Belopolski et al., Nature Physics 10, 943 (2014). 

Observation of topological surface state quantum Hall effect in an intrinsic threedimensional topological insulator. Published in Y. Xu, I. Miotkowski, C. Liu, J. Tian, H. Nam, N. Alidoust, J. Hu, C.K. Shih, M. Z. Hasan and Y. P. Chen, Nature Physics 10, 956 (2014). 

Observation of a threedimensional topological Dirac semimetal phase in highmobility Cd_{3}As_{2}. Published in M. Neupane, S.Y. Xu, R. Sankar, et al., Nature Commun. 5, 3786 (2014). 

Observation of quantumtunnellingmodulated spin texture in ultrathin topological insulator Bi2Se3 films. Published in M. Neupane, A. Richardella, J. SanchezBarriga, et al., Nature Commun. 5, 3841 (2014). 

Observation of monolayer valence band spinorbit effect and induced quantum well states in MoX_{2} Published in Nasser Alidoust, Guang Bian, SuYang Xu, et al., Nature Commun. 5, 4673 (2014) 

First spectroscopic observation of topological surface states in a topological Kondo insulator SmB_{6}. Published in M. Neupane, N. Alidoust, S.Y. Xu, et al., Nature Commun. 4, 2991 (2013). 

Magnetic Topological Insulators: Hedgehog spin texture and Berry's phase tuning in a magnetic topological insulator Published in S.Y. Xu, M. Neupane, C. Liu, et al., Nature Physics 8, 616 (2012). 



Observation of a topological crystalline insulator phase and topological phase transition in Pb_{1x}Sn_{x}Te Published in SuYang Xu, Chang Liu, N. Alidoust, et al., Nature Commun. 3, 1192 (2012) 

HalfHeusler ternary compounds as new multifunctional experimental platforms for topological quantum phenomena. Published in H. Lin, L. A. Wray, Y. Xia, et al., Nature Materials 9, 546 (2010). 

Observation of topological order in a superconducting doped topological insulator. Published in L. A. Wray, S.Y. Xu, Y. Xia, et al., Nature Physics 6, 855 (2010). 

Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator. S.Y. Xu, Y. Xia, L. A. Wray et al.; Science 332, 560 (2011) 

A tunable topological insulator in the spin helical Dirac transport regime. D. Hsieh, D. Qian, Y. Xia, et al.; Nature 460, 1101 (2009) 



Berry's phase and quantization in topological insulators. M. Zahid Hasan Physics 3, 62 (2010) 

The first 3D topological insulator: Bi_{1x}Sb_{x} D. Hsieh, D. Qian, Y. Xia, et al., Nature 452, 970 (2008) D. Hsieh, Y. Xia, L. A. Wray, et al., Science 323, 919 (2009) 

Demonstration of a Fully Bulk Insulating (Intrinsic) Topological Insulator 

Observation of topological surface state quantum Hall effect in an intrinsic threedimensional topological insulator. Published in Y. Xu, I. Miotkowski, C. Liu, J. Tian, H. Nam, N. Alidoust, J. Hu, C.K. Shih, M. Z. Hasan and Y. P. Chen, Nature Physics 10, 956 (2014). 

Protected helical Dirac fermions as a topological boundary mode Nature Physics N&V 
Advanced AngleResolved Photoemission Spectroscopy (ARPES) and Quantum Topology 

A novel experimental approach to topological quantum phenomena: Traditionally spectroscopic methods have been used to characterize electronic behavior in quantum matter whereas initial discoveries originated from transport methods. Our works in 3D topological insulators suggest that spectroscopic methods such as ARPES can be utilized to discover novel topological quantum phenomena (Science 323, 919 (2009), Nature 452, 970 (2008), Nature 460, 1106 (2009), Science 332, 560 (2011)). Previously topological quantum phenomena (quantum Hall like effects) were being probed mainly with transport methods pioneered by von Klitzing (1980). Following our demonstration of application of spinARPES, there are worldwide efforts to apply this technique and its derivatives to probe and study novel topological quantum phenomena in condensed matter systems.


Review/Perspective Articles (Invited):
Topological Insulators, Topological Dirac semimetals, Topological Crystalline Insulators, and Topological Kondo Insulators
M. Z. Hasan, S.Y. Xu, M. Neupane
Book Chapter in Topological Insulators, Fundamentals and Perspectives (John Wiley & Sons) (2015)
Topological Insulators, Helical Topological Superconductors and Weyl Fermion Semimetals
M. Z. Hasan, S.Y. Xu and G. Bian
Phys. Scr. T164 014001 (2015)
Experimental Discoveries: Topological Surface States  A New Type of 2D Electrons Systems
M. Z. Hasan, S.Y. Xu, D. Hsieh, L. Wray, Y. Xia
Book Chapter in Topological Insulators (Elsevier/Oxford) (2013)
Topological Quantization in Topological Insulators
M. Z. Hasan
Physics 3, 62 (2010)
ThreeDimensional Topological Insulators
M. Z. Hasan and J. E. Moore
Ann. Rev. Cond. Mat. Phys 2, 55 (2011)
Topological Insulators (Colloquium Article)
M. Z. Hasan and C. L. Kane
Rev. Mod. Phys 82, 3045 (2010)
Discovery of Weyl fermion semimetals and Topological Fermi arcs
M. Z. Hasan, S.Y. Xu and I. Belopolski
Weyl semimetals, Fermi arcs and chiral anomaly
S. Jia, S.Y. Xu, M. Z. Hasan
Nature Materials 15, 11401144 (2016) (Cover Image & Story)