M. Zahid Hasan
 Physics
I am interested in the fundamental physics of exotic quantum matter, interacting electron systems (correlated matter) and quantum nature of emergent phenomena in these systems.
Scattering based spectroscopic methods are used in the investigations of novel quantum phases realized via topological ordering, stronginteraction or geometrical frustration and their combinations. Quantum Hall phases, correlated superconductors and frustrated magnets have profoundly changed our microscopic understanding of interacting quantum matter. My research is focused on the frontiers and new discoveries of fundamental physics such as the quantum Halllike effect without external magnetic field, understanding nonBCS superconductivity in correlated materials and fractionalized phases in higher dimensions as well as the development of innovative/advanced instrumentation capability necessary to address these issues. I am interested in the stateoftheart storagering Synchrotrons and nextgeneration linearAccelerator based Xray FELs for their potential use/application in fundamental physics. At Princeton, I am also affiliated with the institute of technology PRISM and the engineering physics program.
Traditionally spectroscopic methods have been used to characterize electronic or spin behavior in quantum matter whereas initial discoveries originated from nonspectroscopic methods. My work focuses on the theme which I often like to call spectroscopy for discovering new states of quantum matter. I am currently interested in quantum spintextures & Berry phases of matter, Topological Insulator, topological Hall phases, topological superconductors and quantum phase transitions leading to these topological phases; Emergence of superconductivity in strongly correlated triangular lattice materials (correlated superconductors) and spinliquidlike behavior in frustrated magnets in search of direct/unambiguous signatures of electron fractionalization or new fractional phases in higher dimensions.
Topological Matter
Topological Surface States : Topological Insulators and Superconductors
New Forms of Matter : Topological Insulators & Superconductors
Experimental Discovery : Topological Surface States  A New Type of 2D Electron Systems
Topological Insulators, Topological Crystalline Insulators & Topological Kondo Insulators
Three dimensional topological insulators (3DTI) (originally called "Topological Insulators" to dinstinguish them from 2D quantum Hall type effects and insulators) are the first example of topological order in the bulk solids (there is no genuine quantum Hall effect in three dimensions). They feature a "protected" metallic Diraclike surface state (2DEG or planar "topological metal") where electron’s spin and momentum are locked to each other and possess half the degrees of freedom present in an ordinary electron Fermi gas. Strong spinorbit coupling leads to an insulating bulk and the surface states are protected by time reversal symmetry and belong to the Z2 class (see theory by FuKane'07, MooreBalents'07; KaneMele'05; precursor theory of TRbreaking 2D topological insulator of quantum (anom.) Hall effect by Haldane in 1988). In experiments, 3D Topological Insulators are an example of nonquantumHalllike topological matter experimentally discovered and reported (2007) around the same time, in parallel, as the spin Hall edgestates in Hg(Cd)Te, in 2007. Both the Spin Hall effect (Wurzburg team) and 3D Topological Insulator Surface States (my team, Nature 452, 970 (2008), submitted in 2007, "Search&Discovery" Physics Today and KITP 2007) were reported the same year 2007 using two independent and unrelated experimental methods. Experimentally, these two are unrelated. The spin quantum Hall effect (QSHE) can be thought of as two copies of wellknown IQH (integer quantum Hall) states put together in two dimensions. Since IQH state is a 2D topological insulator, spin quantum Hall effect is also a 2D topological insulator but timereversal invariant (protected by Z2 invariant). On the other hand, the 3D Topological Insulators are a new and distinct state of matter which cannot be reduced to multiple copies of IQH and there is no spin Hall effect in 3D (the term "Topological Insulators" was originally used exclusively for the novel and unprecedented 3D state since there is no spin Hall like effect there). The 3D state is thus an example of nonquantumHalllike topological matter and the first realization of topologically ordered bulk solid in nature (Physics World 2011). Experimentally, 3D TI did not arise from quantum spin Hall effect.
NonquantumHalllike topological matter:
All of the 2D topological insulator examples (IQH, FQH, QSH or the QAH) including the fractional one (FQH) involving Coulomb interaction are understood in the standard picture of quantized electron orbits in a spinindependent or spindependent magnetic field, the 3D topological insulator defies such description and is a novel type of topological order which cannot be reduced to multiple copies of quantumHalllike states. In fact, the 3D topological insulator exists not only in zero magnetic field, they also differ from the 2D variety in three very important aspects:
1) they possess topologically protected 2D metallic surfaces (a new type of 2DEG) rather than the 1D edges, 2) they can work at room temperature (300K and beyond, largegap topological insulators) rather than cryogenic (mK) temperatures required for the QSH effects and,3) they occur in standard bulk semiconductors rather than at buried interfaces of ultraclean semiconductor heterostructures thus tolerate stronger disorder than the IQHlike states.
The nonquantumHalllike (novel) character and the extremely rich physics (surface 2DEG, helical fermion gas) of the 3D state has led to a worldwide research interest in this topic in general. Also the novel experimental approach in studying topological quantum phenomena demonstrated by us are now being used by many other groups worldwide studying many other topological materials and phenomena.
Why Topological Surface States (TIs) are so exciting?
Topological Insulators (3DTI) is new and unprecendented and cannot be reduced to multiple copies of quantum Hall or spin Hall like states. Most topological states of matter are realized in two or lower dimensions (quantum Hall states, quantum spin Hall effect, nonFermi liquid chains and wires, quantum spinliquids etc.). Unlike all others, neither strong electronelectron interactions (necessary for quantum spin liquids), high magnetic fields and low temperatures (necessary for quantum Hall states), nor low dimensionality (needed for quantum Hall states, spin quantum Hall states (QSHE), and nonFermi liquid spin chains) are needed for the 3D topological insulator. The theoretical and experimental discovery of the 3D TIs – the first example of topological order in bulk solids  has generated much experimental and theoretical efforts to understand and utilize all aspects of these quantum phenomena and the materials that exhibit them.
One of the major challenges in going from quantum Halllike 2D states to 3D topological insulators is to develop new experimental approaches/methods to precisely probe this novel form of topologicalorder since the standard tools and settings that work for IQHstate also work for QSH states. The method to probe 2D topologicalorder is exclusively with charge transport (pioneered by Von Klitzing in the 1980s), which either measures quantized transverse conductance plateaus in IQH systems or longitudinal conductance in quantum spin Hall (QSH) systems. In a 3D topological insulator, the boundary itself supports a two dimensional electron gas (2DEG) and transport is not (Z2) topologically quantized hence cannot directly probe the topological invariants νo or the topological quantum numbers analogous to the Chern numbers of the IQH systems. This is unrelated to the fact that the present materials have some extrinsic or residual/impurity conductivity in their naturally grown bulk. In this paper, we review the birth of momentum and spinresolved spectroscopy as a new experimental approach and as a directly boundary sensitive method to study and prove topologicalorder in threedimensions via the direct measurements of the topological invariants νo that are associated with the Z2 topology of the spinorbit band structure and opposite parity band inversions, which led to the experimental discovery of the first 3D topological insulator in Bibased semiconductors.
Topological Surface States (A New Type of 2D Electron System) & Topological Insulators: Experimentally demonstrated, a three dimensional topological insulator (3DTI) features a protected twodimensional electron gas on its surface. The high magnetic fields, low temperatures or low dimensionality are not necessary for retaining the topological protection or topological order of a macroscopic 2DEG on the surface of a topological insulator.
Nature 452, 970 (2008), submitted in 2007, also KITP 2007
"Search&Discovery" Physics Today
Experimental Discovery : Topological Surface States  A New Type of 2D Electron Systems
Measurements of topological invariants {vo}: Transport measurements that have been the key to probe topological order in conventional quantum Hall like systems cannot (even in theory!) be used to measure the topological quantum numbers of Z2 TIs (FuKane’s {vo}). We have shown a technique/method for the direct measurement of Z2 topological quantum numbers {vo} for the first time:
Science 323, 919 (2009), later further expanded: Science 332, 560 (2011) see below for details.
Topological (Z2) Order is more directly manifested in the spin and momentum correlated motion of electrons on the surface. This leads to a new type of 2DEG where the electron’s spin and linear momentum are onetoone locked. Such a 2DEG only carries half of the total degrees of freedom of a conventional 2DEG and in the vicinity of the Kramers’ point takes the form of a half Dirac gas:
Nature 460, 1101 (2009) and further details in related materials Phys. Rev. Lett. (2009)
News in Physics Today
Consequence of Z2 topological order: SpinMomentum locking and piBerry's phase lead to the absence of elastic backscattering on the surfaces. By combining spinARPES and tunneling (collaboration), we have demonstrated such absence of elastic backscattering:
Nature 460, 1106 (2009) (STM+SpinARPES), Berry's phase was shown at Science 323, 919 (2009)
Discovery of the next generation and “room temperature topological insulators”: the Bi2Se3 class: The advantages of large band gap and simple spinpolarized Dirac cone topology of these spinorbit insulators led to our observation of topological quantum phenomena at room temperatures without magnetic fields and without high purity semiconductors
Discovery of SingleDiracCone TSS Bi2Se3 as a TI class: N&V NatPhys (2009)
KITP Proc. 2008 "The Hydrogen Atom of Topological Insulator" BiSb (2007) to Bi2Se3 KITP (2008)
Nature Physics 5, 398 (2009) submitted in 2008 and (see above Nature (2009))
Phys. Rev. Lett. 103, 146401 (2009) further work on Bi2Te3 and Sb2Te3 in comparison with Bi2Se3
Phys. Rev. Lett. 105, 036404 (2010) Bi2Se3 related TIs such as spinorbit BiTlSe2 class of materials
Given that the topological insulators are standard bulk semiconductors and their topological characteristics can survive to high temperatures, their novel properties could lead to many exciting applications. An exciting progress along this line is that the Bi2Se3 class of 3D TIs can be turned in to superconductors to form the host material for Majorana Fermions (Nature Physics 6, 855 (2010)). Also both integer and fractional quantum Hall effects have been reported in this Bi2Se3 class of materials by other groups indicating the high mobility of the topological surface state. These developments have unleashed a worldwide experimental effort to understand all aspects of electrical and spin properties leading to a nearly graphenelike revolution in physics (Physics World 2011).
Magnetic Symmetry Breaking: Topological protection and degree of robustness: The Dirac cone materials are probed via the modification of surface potential: How robust the topological properties of a Topological Insulator surface are investigated (Nature Physics 7, 32 (2011)). This paper reported preliminary results regarding magntism, for a full detail see, Magnetic Topological Insulators : The effect of timereversal symmetry leads to unconventional spin textures on the surface of a topological insulator. Hedgehog spin texture and Berry’s phase tuning in a magnetic topological insulator was observed in our experiments;
Nature Physics 7, 032 (2011) Coulomb/disorder/magnetic perturbation effects.
Nature Physics 8, 616 (2012) for Magnetic symmetry breaking, for details see Phys. Rev. B (2012)
Bulk Insulating Topological Insulators: Recently, highly bulk insulating topological insulators have also been realized where Dirac surface states contribute more than 70% of the total conduction channel (Preprint at Xiong et.al., arXiv:1101.1315v1 on Bibased 3D TIs identified by us, Preprint at S.Y. Xu et.al., arXiv:1007.5111v1 (2010) which led to our work reported at Phys. Rev. B (2012)). Also see works by other groups Phys. Rev. B (2010) [ our eariler ARPES on Bi2Te2Se at arXiv (2010)]
Adiabatic Continuation Method for Predicting TI & Topological Phase Transition: Working with Hsin Lin and others we demonstrated that firstprinciples based adiabatic continuation approach is a very powerful and efficient tool for constructing topological phase diagrams and locating nontrivial topological insulator materials. Applied to real materials our results demonstrated the efficacy of adiabatic continuation as a useful tool for exploring topologically nontrivial alloying systems and for identifying new topological insulators even when the underlying lattice does not possess inversion symmetry, and the approaches based on parity analysis of FuKane are not viable.
Science 332, 560 (2011) and in a related system, see
Phys. Rev. Lett. 109, 186403 (2012)
Z2 topological insulator protected by timereversal symmetry is realized via spin–orbit interactiondriven band inversion. The topological phase in the Bi_{1−x}Sb_{x} system is due to an odd number of band inversions. We experimentally investigated the possibility of a mirror symmetryprotected topological crystalline insulator phase in the Pb_{1−x}Sn_{x}Te class of materials that has been theoretically predicted (by Fu et.al.,) to exist in its end compound SnTe. Our observation of the spinpolarized Dirac surface states in the inverted Pb_{1−x}Sn_{x}Te and their absence in the noninverted compounds related via a topological phase transition provide the experimental groundwork for opening the research on novel topological order in quantum devices.
Nature Commun. 03, 1192 (2012) TCIphase and BI to TCI Phase Transition
Science 332, 560 (2011) and more recently in other materials such as Cd3As2 (see below)
Nature Commun. 05, 3786 (2014) topological 3D Dirac Semimetal Cd3As2
Preprint on Na3Bi (2013) topological 3D Dirac Semimetal Na3Bi
Nature Commun. 05, 3786 (2014) Relativistic nanoscale Schottky barrier (with M. Marsi group)
Preprint (2014) Exotic ultrafast response of TIs (our recent work)
Nature Physics 8, 616 (2012) Magnetic Thin Films
Nature Commun. 05, 3786 (2014) Tunelling and spintexture evolution in films for potential devices.
Nature Commun. (press) (2014) Spinorbit physics in molydiselenide films for potential devices.
Nature Commun. 04, 2991 (2013)
An expt. algorithm for topo Kondo & mixedval. insulators (2013)
RESEARCH AREAS
Quantum SpinTextures, Topological matter and Quantum spin Hall phase, Superconductivity in Topological Matter: Experimental methods and direct imaging/determination of topological order character of the topological Thetavacuum, axionfields and spin Hall phases. Experimental realizations of Quantum Hall effect without Landau levels. Ternary and binary alloys of bismuth, halfHeuslers and related compounds. Doping of a topological Hall state. Quantum Halllike effect without external magnetic fields. Superconductivity in doped topological insulators.
Topological Berry's Phases and spinhelicalDirac Fermions for Quantum Information: Dirac physics in nonGraphene systems (graphene has a vanishingly small spinorbit coupling). Domain wall Fermions, Chiral fermions, Parity anomaly without Fermion doubling. Spontaneous Rashba effects etc. Doping of a Dirac spectrum. MaterialPhysics matrix for topological (faulttolerant) Quantum Computing. Topological Spintextures.
Electrons on Frustrated spin1/2 Lattices and Novel Superconductors: Fermiology and quasiparticle dynamics, Collective charge and spin excitations in strongly interacting quantum electron systems. Mott phenomena, metalinsulator transition, chargeorder, superconductivity, high thermopower, spindependent thermoelectricity, OrderbyFrustration, quantum zero modes. Doped cobaltates, chromates and related compounds.
Novel routes/mechanism to High T_{c}^{ }Superconductivity: Momentumdependence of superconducting gap, orderparameter, Fermiology and quasiparticle dynamics, Collective charge and spin excitations in FeAs pnictides. SDW Superconductor competition, coexistence, Pairing mechanism and quantum magnetism. Quasiparticle scattering with collective modes. OrderbyFrustration, quantum zero modes. Iron pnictides, ironchalcogenides and related high Tc superconductors.
Competition/Coexistence of Superconductivity and CDW/SDW : Nonnested CDWs, Commensurate CDWs in two dimensions, Excitonic CDW as a competing order to superconductivity, spindependent thermoelectricity, KohnOverhauser phases, Chargeorder and superconductivity: Doped cobaltates, Titanate TMDs and related compounds. (Phys.Rev.Lett.s 2007a,b,c, preprints 2010).
Electron Fractionalization (holons) and Collective charge excitations coupled to Xrays: Direct detection of spinless collective charge modes in 1D spin1/2 Mott insulator via full Brillouin zone imaging in inelastic resonant xray scattering demonstrated (Phys.Rev.Lett. 2002, IJMPB 2003, preprints 2010). Direct signature of Holons (Electron fractionalization/collective mode)
Collective Charge Modes in doped Mott insulators via highresolution Xray spectroscopy: Xray Imaging techniques. Development of high resolution bulksensitive momentumresolved Xray techniques to probe collective charge excitation modes in doped Mott insulators, Cuprates near AFM/SC transition. Full Brillouin zone imaging in inelastic resonant xray scattering demonstrated. Electron Fractionalization and Collective excitations: Direct detection of spinless collective charge modes in 1D spin1/2 Mott insulator via full Brillouin zone imaging in inelastic resonant xray scattering demonstrated (Science 2000, Phys.Rev.Lett./Bs 20022008, preprints 2010). Mott physics via momentumresolved Inelastic resonant Xray scattering demonstrated,Science 2000.
Advanced scattering probes (Synchrotron Xray photons, electrons, neutrons) are used to study order and excitations of correlated electrons in various condensed matter systems. Scattering probes allow one to measure various orders of correlation functions and order parameters and reveal the quantum numbers (energy, momentum or spin) of electrons in crystals which describes the phase (Fermi surface topology, quasiparticle selfenergy etc.) or some collective excitations such as magnons, phonons, plasmons or holons/solitons over the entire Brillouin zones (allowing to classify the brokensymmetry phases). Precise experimental measurements of dispersion relations (E vs. k or Q) of these elementary quantum and collective excitation modes provide fundamental insights about the microscopic physics of the complex systems. We use three principal classes of techniques: (1) Angleand SpinResolved, UV and Xray Photoemission (at ALS, SSRLSLAC, SLS and SRC); (2) Inelastic, Elastic, Resonant Xray Scattering (at ALSLBNL, APS, SSRL, LCLS(future)); (3) Neutron Scattering with magnetic fields (at NIST, ISISOxford). Experiments are performed at national and international laboratories (ALSLBNL, SSRL/SLAC, Argonne, Brookhaven, ESRF/France, NIST, Spring8/Japan, ISIS/Oxford), as well as at the Joseph Henry Labs at Princeton. We are currently developing two novel high resolution (~10100 meV) stateoftheart synchrotron Xray scattering spectrometers  one to work around 1 KeV and another around 100 eV at the Advanced Light Source of LBL (MERLIN soft Xray stateoftheart synchrotron beamline (at Adv. Light Source). We are also scientific members of scattering consortia at APS/ANL, ALSLBNL, SSRLSLAC and LCLS.
Selected Publications
Topological Matter and Topological Quantum Phenomena:
 Topo. Insulators, Topo. Crystalline Insulators & Topo. Kondo Insulators Preprint (2014)
 Topological Insulators; M.Z. Hasan, C.L. Kane; Rev. Mod. Phys 82, 3045 (2010)
 Topological Quantization in Topological Insulators; M.Z. Hasan Physics 3, 62 (2010).
 ThreeDimensional Topological Insulators; M.Z. Hasan, J.E. Moore Ann. Review. Cond. Mat. Physics (2011).
 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)
 Observation of a topological 3D Dirac semimetal phase in Cd3As2;
M. Neupane, SuYang Xu, Raman Sankar, Nasser Alidoust, Guang Bian, Chang Liu, Ilya Belopolski, TayRong Chang, HorngTay Jeng, Hsin Lin, Arun Bansil, Fangcheng Chou, M. Z. Hasan Nature Commun. 5, 3786 (2014)
 Observation of bulk 3D Dirac multiplet, topological semimetal phase and spin states in Na3Bi M. Neupane, SuYang Xu, Raman Sankar, Nasser Alidoust, Guang Bian, Chang Liu, Ilya Belopolski, TayRong Chang, HorngTay Jeng, Hsin Lin, Arun Bansil, Fangcheng Chou, M. Z. Hasan Preprint (2013)
 Tuning a Schottky barrier in a photoexcited topological insulator with transient Dirac cone electronhole asymmetry (Timeresolved ARPES) Y. M. Hajlaoui, E. Papalazarou, J. Mauchain, L. Perfetti, A. TalebIbrahimi, F. Navarin, M. Monteverde, P. AubanSenzier, C.R. Pasquier, N. Moisan, D. Boschetto, M. Neupane, M.Z. Hasan, T. Durakiewicz, Z. Jiang, Y. Xu, I. Miotkowski, Y.P. Chen, S. Jia, H.W. Ji, R.J. Cava, M. Marsi; Nature Commun. 5, 3003 (2014).
 Observation of QuantumTunneling Modulated Spin Texture in Ultrathin Topological Insulator Bi2Se3 Films ;Madhab Neupane, Anthony Richardella, Jaime SánchezBarriga, SuYang Xu, Nasser Alidoust, Ilya Belopolski, Chang Liu, Guang Bian, Duming Zhang, Dmitry Marchenko, Andrei Varykhalov, Oliver Rader, Mats Leandersson, Thiagarajan Balasubramanian, TayRong Chang, HorngTay Jeng, Susmita Basak, Hsin Lin, Arun Bansil, Nitin Samarth, M. Zahid Hasan Nature Commun. 5, 3003 (2014).

Surface States in a Topological Kondo Insulator Candidate; M Neupane, N Alidoust, SY Xu, T Kondo, DJ Kim, Chang Liu, I Belopolski, TR Chang, HT Jeng, T Durakiewicz, L Balicas, H Lin, A Bansil, S Shin, Z Fisk, MZ Hasan Nature Commun. 04, 2991 (2013).
Observation of Dirac node formation and mass acquisition in a topological crystalline insulator Y. Okada, M. Serbyn, H. Lin, D. Walkup, W. Zhou, C. Dhital, M. Neupane, Suyang Xu, Y. Wang, R. Sankar, F. Chou, A. Bansil, M. Z. Hasan, S. Wilson, Liang Fu, V. Madhavan Science 341, 1496 (2013).
 Magnetic Topological Insulators: Hedgehog spin texture and Berry’s phase tuning in a magnetic topological insulator; SuYang Xu, M. Neupane, C. Liu, D. Zhang, A. Richardella, L. A. Wray, N. Alidoust, M. Leandersson, T. Balasubramanian, J. SánchezBarriga, O. Rader, G. Landolt, B. Slomski, J.H. Dil, J. Osterwalder, T.R. Chang, H.T. Jeng, H. Lin, A. Bansil, N. Samarth, M. Z. Hasan Nature Physics 08, 616 (2012).

Topological Crystalline Insulators protected by mirror symmetry: Observation of Topological Crystalline Insulator phase in Pb1xSnxTe : SuYang Xu, C. Liu, N. Alidoust, D. Qian, M. Neupane, J. D. Denlinger, Y. J. Wang, L. Wray, R. J. Cava, H. Lin, A. Marcinkova, E. Morosan, A. Bansil, M. Z. Hasan Nature Commun. 03, 1192 (2012).
 Topological Phase Transition & TextureInversion; Topological phase transition and texture inversion in a tunable topological insulator. Xu SY, Xia Y, Wray LA, Jia S, Meier F, Dil JH, Osterwalder J, Slomski B, Bansil A, Lin H, Cava RJ, Hasan MZ.; Science 332, 560 (2011).
 Superconducting doped Topological Insulator; Observation of unconventional band topology in a superconducting doped topological insulator, CuxBi2Se3: Topological Superconductor or nonAbelian superconductor? L.A. Wray, S. Xu, Y. Xia, D. Qian, H. Lin, A. Bansil, Y. Hor, R.J. Cava, M.Z. Hasan Nature Physics 6, 855 (2010); Science Editor's Choice (2010).
 A new platform for topological quantum phenomena : Topological Insulator states in thermoelectric Heuslerrelated ternary compounds; H. Lin, L.A. Wray, Y. Xia, S. Jia, R.J. Cava, A. Bansil, M.Z. Hasan; Nature Materials 9, 546 (2010), NaturePhys News (2010).

A topological insulator surface under strong Coulomb, magnetic and disorder perturbations L.A. Wray, S. Xu, Y. Xia, D. Qian, H. Lin, A. Bansil, Y. Hor, R.J. Cava, M.Z. Hasan NaturePhysics (2010). NaturePhys News (2011).
 SingleDiracCone topological surface states on TlBiSe_{2}class Thalliumbased IIIVVI2 Ternary Chalcogenides H. Lin, R.S. Markiewicz, L.A. Wray, L. Fu, M.Z. Hasan, A. Bansil; Phys. Rev. Lett. 105, 03640 (2010).
 A new class of Topological insulators: SingleDiraccone Z_{2} topological insulator phases in distorted Li_{2}AgSbclass and related quantum critical Libased spinorbit compounds; H. Lin, L.A. Wray, Y. Xia, S.Y. Xu, S. Jia, R.J. Cava, A. Bansil, M.Z. Hasan; arXiv:1004.0999v1 (2010).
 Helical Dirac Fermions: A tunable topological insulator in the helical Dirac fermion topological transport regime (spinARPES evidence of direct detection of topological order) D. Hsieh, Y. Xia, D. Qian, L. Wray, J. H. Dil, F. Meier, L. Patthey, J. Osterwalder, A.V. Fedorov, H. Lin, A. Bansil, D. Grauer, Y.S. Hor, R.J. Cava, M.Z. Hasan
Nature 460, 1101 (2009).
An Insulator's Metallic side (Topological Insulator): Nature 460, 1090 (2009).
Lightlike SpinTextured Fermions and Quantum Halllike Effect (2009)  SpinTextures, Topological Order & Topo Insulators Physics Today (2009)
 Topological Insulators: The Next Generation Nature Physics (2009)
 Absence of Backscattering and Topological Protection: Topological surface states protected from backscattering by Chiral SpinTextures (STM+spinARPES); P. Roushan, J. Seo, C.V. Parker, Y.S.Hor, D. Hsieh, A. Richardella, D. Qian, M.Z. Hasan, R.J. Cava, A. Yazdani (STM+spinARPES)
Nature 460, 1106 (2009).
Nature (Perspective) 2009  Topological SpinTextures & pi Berry's phase observation: Observation of Unconventional Quantum Spin Textures in a Topological Insulator : Probing the "spin" degrees of freedom in a quantum spin Hall system, D. Hsieh, Y. Xia, L. Wray, D. Qian, A. Pal, J. H. Dil, F. Meier, J. Osterwalder, G. Bihlmayer, C. L. Kane, Y. S. Hor, R. J. Cava and M. Z. Hasan
Science 323, 919 (2009).
Fast Electrons Tie Quantum Knots Science (Perspectives), J. Zaanen
Quantum Twist (news), Topological Spintextures in Momentumspace : SpinresolvedARPES  Spinpolarized SingleDiracCone: Observation of timereversalprotected singleDiraccone topologicalinsulator states in Bi_{2}Te_{3} and Sb_{2}Te_{3}; Y. Xia, L. Wray, D. Qian, D. Hsieh, H. Lin, A. Bansil, D. Grauer, Y. Hor, R. J. Cava, M. Z. Hasan
Physical Review Letters 103, 146401 (2009).  Discovery of Bi_{2}Se_{3} class possessing TopologicalOrder: Observation of a largegap topologicalinsulator class with a single surface Dirac cone; Y. Xia, L. Wray, D. Qian, D. Hsieh, H. Lin, A. Bansil, D. Grauer, Y. Hor, R. J. Cava, M. Z. Hasan
Nature Physics 5, 398402 (2009).
Topological Insulators: The Next Generation, J.E. Moore Nature Physics 5, 378380 (2009).  A Topological Dirac insulator in a Quantum Spin Hall Phase, D. Hsieh, D. Qian, L. Wray, Y. Xia, Y. Hor, R.J. Cava and M.Z. Hasan
Nature 452, 970 (2008) [Submitted in 2007]
Highenergy physics in a new guise, M. Franz, Physics 1, 36 (2008)
Observation of a New Phase of Matter : Quantum Halllike effects w/o Magnetic Field
Strongly Correlated (ManyBody) Electrons and Novel High T_{c} superconductors :

Fermisurface topology and lowlying electronic structure of the ironbased superconductor Ca10(Pt3As8)(Fe2As2)5; M. Neupane, C. Liu, S.Y. Xu, Y.J. Wang, Ni Ni, J. M. Allred, L. A. Wray, N. Alidoust, H. Lin, R. S. Markiewicz, A. Bansil, R. J. Cava, and M. Z. Hasan Physical Review B 85, 094510 (2012).
Dirac cone in ironbased (pnictide) superconductors, M. Z. Hasan and B. A. Bernevig
Physics 3, 27 (2010). (PRL Viewpoint)OrbitalTextures in Pnictides: Observation of intertwined Fermi surface topology, orbital parity symmetries and electronic interactions in iron arsenide superconductors; L.A. Wray, D. Hsieh, Y. Xia, S.Y. Xu, D. Qian, G. F. Chen, J. L. Luo, N. L. Wang, M.Z. Hasan; arXiv:0912.5089v1 (2009).
 Superconducting Gap in Pnictides: Momentum dependence of Superconducting Gap, strongcoupling dispersion Kink, and tightly bound Cooper pairs in the highT_{c} (Sr,Ba){1x}(K,Na)xFe_{2}As_{2} superconductors, L. Wray, D. Qian, D. Hsieh, Y. Xia et.al.,
Physical Review B 78, 184508 (2008) [Editor's Highlight]  SpindensityWave (nodal state) in Pnictides: Determination of electronic groundstate of magnetically ordered parent iron pnictides, D. Hsieh, Y. Xia, L. Wray, D. Qian, G. F. Chen, J. L. Luo, N. L. Wang, M. Z. Hasan
Nature, (in review) http://aps.arxiv.org/abs/0812.2289  Fermi Surface Topology and LowLying Quasiparticle Dynamics of Parent Fe(Te)Se Superconductor, Y. Xia, D. Qian, L. Wray, D. Hsieh, G. F. Chen, J. L. Luo, N. L. Wang, M. Z. Hasan
Physical Review Letters, 103, 037002 (2009).
Not all iron superconductors are the same: Physics 2, 59 (2009)
Physics of Competing Order : Chargeorder and Superconductivity:
 Emergence of Fermi Pockets in a New Excitonic CDW Melted Superconductor Cu_{x}TiSe_{2 }_{, }D. Qian, D. Hsieh, L. Wray, Y. Xia, N.L. Wang, E. Morosan, R.J. Cava and M.Z. Hasan
Physical Review Letters 98, 117007 (2007).  Evidence for an Overhauser phase –a semimetaltosemimetal CDW transition in the parent compound of Cu_{x}TiSe_{2}_{, }G. Li, W. Hu, D. Qian, D. Hsieh, M.Z. Hasan, E. Morosan, R.J. Cava, N.L. Wang
Physical Review Letters 99, 027404 (2007).  Quasiparticle’s quantum coherence and dynamics in the vicinity of metalinsulator phase transition in Na_{x}CoO_{2}_{ }D. Qian, L. Wray, D. Hsieh, A. Kuprin, A. Fedorov, D. Wu, J. L. Luo, N.L. Wang, L. Viciu, R.J. Cava and M.Z. Hasan
Physical Review Letters 96, 046407 (2006).
Correlated electrons on triangular lattices: Quantum Charge Frustration
 Complete dBand dispersion relation and small Fermion scale in Na_{x}CoO_{2}_{, }D. Qian, L. Wray, D. Hsieh, L. Viciu, R.J. Cava, J.L. Luo, D. Wu, N.L. Wang, and M.Z. Hasan
Physical Review Letters 97, 186405 (2006).  Lowlying quasiparticle modes and hidden collective charge instabilities in parent cobaltates superconductors Na_{x}CoO_{2}_{, }D. Qian, D. Hsieh, L. Wray, Y.D. Chuang, A. Fedorov, D. Wu, J.L. Luo, N.L. Wang, L. Viciu, R.J. Cava and M.Z. Hasan
Physical Review Letters 96, 216405 (2006).  Fermi surface topology and quasiparticle dynamics of host Na_{x}CoO_{2} investigated by ARPES, M. Z. Hasan, Y.D. Chuang, D. Qian, Y.W. Li, Y. Kong, A. Kuprin, A.V. Fedorov, R. Kimmerling, E. Rotenberg, K. Rossnagel, Z. Hussain, H. Koh, N.S. Rogado, M.L. Foo, and R. J. Cava
Physical Review Letters 92, 246402 (2004).
Resonant Xray Scattering and Charge Collective Modes :

R. Reininger Coexistence of pseudogap, chargetransfer gap, and Mottgap energy scales in the resonant inelastic Xray profile of electron doped cuprate superconductors S. Basak, T. Das, H. Lin, M.Z. Hasan, R.S. Markiewicz, and A. BansilPhysical Review B 85, 075104 (2012).

Momentumresolved Charge Modes (Holons) in a Prototype 1D Mott Insulator Studied by Inelastic Resonant Xray Scattering, M.Z. Hasan, P.A. Montano, E.D. Isaacs, Z.X. Shen, S. Sinha, Z. Islam, H. Eisaki, N. Motoyama and S. UchidaPhysical Review Letters 88, 177403 (2002).

Electronic Structure of Mott Insulators Studied by Inelastic (Resonant Inelastic) Xray Scattering,M.Z. Hasan, E.D. Isaacs, Z.X. Shen, L.L. Miller, K. Tsutsui, T. Tohyama and S. MaekawaScience 288, 1811 (2000).

Xray imaging of dispersive charge modes in a doped Mott insulator near the antiferromagnet/superconductor transition, Y.W. Li, L. Wray, D. Qian, D. Hsieh, Y. Xia, H. Eisaki, et.al.,Physical Review B 78, 073104 (2008).

R. Reininger, Y,D. Chuang, Z. Hussain et al., MERLIN soft Xray beamline : A meV Resolution Beamline for Xray scattering at the ALSBerkeley (2012)
Neutron Scattering studies of Quantum/Frustrated Magnetism :
Xray Instrumentation & Spectrometer development :
R. Reininger, Y,D. Chuang, Z. Hussain et al., MERLIN soft Xray beamline : A meV Resolution Beamline at the ALS (2012)
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Recent Talks/Tutorials :
Research Group Members :
SuYang Xu
Nasser Alidoust
Ilya Belopolski
Guang Bian
Chang Liu
Madhab Neupane
Pavel P. Shibayev
Samuel Mumford (Senior Thesis, 2014; PhD program at Stanford University)
Zhiming Tan (Senior Thesis, 2008; PhD program at Oxford University)
YuQi Xia (B.S. Columbia; PhD 2010 Princeton)
Ram Shankar (Senior Thesis, 2010, PU Mathematics )
David Hsieh (B.S. Stanford; PhD 2009, Pappalardo Fellow/MIT; Asst. Professor at CalTech 2012)
Dong Qian (Postdoc 2010, Professor at Shanghai China)
L. Andrew Wray (B.S. Berkeley; PhD 2010, LBNL PDFellow/Berkeley; SLAC/Stanford 2013)