• Atomic Physics
• Biophysics Theory and Experiment
• Cond Matter Experiment Faculty
  • Robert H. Austin
  • M. Zahid Hasan
  • Nai Phuan Ong
  • Jason Petta
  • Ali Yazdani
  • Sandra Troian (Chem Eng)
  • Daniel C. Tsui (Elec Eng)
  • Paul M. Chaikin (at NYU)

• Condensed Matter Theory
• Cosmology Experiment
• Cosmology Theory
• High Energy Experiment
• High Energy Theory
• Mathematical Physics
• Particle and Nuclear Astrophysics

• Quantitative and Computational Biology
• Cosmology at Princeton
• Lewis-Sigler Institute
• Princeton Center for Theoretical Science
• Princeton Institute for the Science
  and Technology of Materials

I am interested in the fundamental physics of quantum condensed-matter systems. Scattering based spectroscopic methods are used in the investigations of novel quantum phases realized via topological ordering, strong-interaction 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 frontier aspects of these areas of fundamental physics such as the quantum Hall-like effect without external magnetic field, non-BCS superconductivity in correlated materials and fractionalized phases in higher dimensions as well as the development of novel instrumentation capability necessary to address these issues. I am currently interested in the quantum spin Hall phases (Topological Z2 Order) in strong spin-orbit coupled materials and quantum phase transitions leading to the quantum spin Hall insulators; emergence of superconductivity in strongly correlated triangular lattice materials (Correlated Nodal Superconductors) and spin-liquid-like behavior in frustrated magnet materials (RVB-type fractionalized phases) in search of direct/unambiguous signatures of electron fractionalization in higher dimensions. Examples of topological phases of quantum condensed-matter include charge quantum Hall effect, novel topological insulators, anti-localization effect due to unpaired Dirac fermions, quantum spin Hall effect, helical edge modes and topological quantum phase transitions. Examples of strong-interaction physics include Mott phenomena such as electron fractionalization or competing orders such as SDW/CDW vs. superconductivity and examples of geometrical frustration physics include spin-liquids and its competing orders such as dimer phases or bond-frustration. Topological insulators have recently been proposed as a possible route to fault-tolerant quantum computing and related spin-orbit Dirac materials can potentially provide spin currents for spintronics applications. On the other hand, doped Mott insulators on triangular lattices not only exhibit exotic superconductivity, spin-liquid behavior but also feature high thermopower figure of merit for applications. Currently, there is no obvious application of spin-liquids but some spin-liquids may exhibit “exotic topological order” and fractionalization which is of much interest to me. My recent (2000-present) research work has focused in the following areas: Topological Order in Quantum Spin Hall-like systems: Topological Z2 phases. Experimental methods and direct imaging/determination of topological order character of the Quantum Spin Hall Phase and other inverted spin-orbit insulators on honeycomb lattices. Experimental realizations of Quantum Hall effect without Landau levels. Ternary and binary alloys of bismuth and related compounds. Doping of a topological Hall state. Quantum Hall-like effect without external magnetic fields. (Nature 2008, Nature Physics N&V 2008) Novel Dirac materials for spintronics: Dirac physics in non-Graphene systems (graphene has a vanishingly small spin-orbit coupling). Domain wall Fermions, Chiral fermions, Search for parity anomaly without Fermion doubling. Spontaneous Rashba effects etc. Phase transition between a Bloch insulator and the topological insulator. Doping of a Dirac spectrum. Search for a route to topological Quantum Computing. Competition/Co-existence of Superconductivity and CDW phases: Non-nested CDWs, Commensurate CDWs in two dimensions, Excitonic CDW as a competing order to superconductivity, spin-dependent thermoelectricity, Kohn-Overhauser phases, Charge-order and superconductivity: Doped cobaltates, Titanate TMDs and related compounds. (Phys.Rev.Lett.s 2007a,b,c, preprints 2008). Correlated Electrons on Frustrated Lattices and Novel superconductors: Fermiology and quasiparticle dynamics, Collective charge and spin excitations in strongly interacting quantum electron systems. Mott phenomena, metal-insulator transition, charge-order, superconductivity, high thermopower, spin-dependent thermoelectricity, Order-by-Frustration phenomena, quantum zero modes. Doped cobaltates, chromates and related compounds. (Phys.Rev.Lett.s 2006a,b,c, preprints 2008). Electron Fractionalization, Topological Collective excitations: Direct detection of spinless collective charge modes in 1D spin-1/2 Mott insulator via full Brillouin zone imaging in inelastic resonant x-ray scattering demonstrated (Phys.Rev.Lett. 2002, IJMPB-2003, preprints 2008). Collective Charge Modes in doped Mott insulators: X-ray Imaging techniques. Development of high resolution bulk-sensitive momentum-resolved x-ray techniques to probe collective charge excitation modes in doped Mott insulators, Cuprates near AFM/SC transition. Full Brillouin zone imaging in inelastic resonant x-ray scattering demonstrated (Science 2000, Phys.Rev.Lett./Bs 2002-2008). Novel spectroscopic method development: Designs of coherent light based spectroscopic techniques to probe fundamental issues in condensed-matter physics. Measurement of electron-orbit quantization in magnetic fields. (2007-). Advanced scattering probes (Synchrotron 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 self-energy etc.) or some collective excitations such as magnons, phonons, plasmons or holons/solitons over the entire Brillouin zones (allowing to classify the broken-symmetry 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: Inelastic, Elastic, Resonant & Coherent X-ray Scattering (at ALS & APS) Angle-and Spin-Resolved Photoemission (ARPES) (at ALS, SSRL and SRC) Neutron Scattering with strong magnetic fields (at NIST, ISIS-Oxford) Experiments are performed at national and international laboratories (Argonne, Brookhaven, Lawrence-Berkeley, ESRF/France, SSRL/SLAC, NIST, Spring8/Japan, ISIS/Oxford), as well as at Joseph Henry Labs at Princeton. We are currently developing two novel high resolution (~10-100 meV) state-of-the-art synchrotron X-ray scattering spectrometers - one to work around 1 KeV and another around 100 eV at the Advanced Light Source of LBL (Co-leading the development of MERLIN (at ALS). We are also scientific members of scattering consortia at APS/ANL and LCLS/SLAC. Research Opportunities in the Hasan Lab: Research opportunities exist for highly motivated graduate and undergraduate students. Interested students are encouraged to contact me (mzhasan@princeton.edu.) Condensed Matter

S e l e c t e d   P u b l i c a t i o n s:

D. Hsieh, D. Qian, L. Wray, Y. Xia, Y. Hor, R.J. Cava and M.Z. Hasan A Topological Dirac insulator in a Quantum Spin Hall Phase Nature 452, 970 (2008) Condensed Matter: An insulator with a twist (Topological Insulator), C.L. Kane Nature Physics 4, 348 (2008) Topological States of Quantum Matter, S.-C. Zhang Physics 1, 6 (2008) D. Qian, D. Hsieh, L. Wray, Y. Xia, N.L. Wang, E. Morosan, R.J. Cava and M.Z. Hasan Emergence of Fermi Pockets in a New Excitonic CDW Melted Superconductor CuxTiSe2 Physical Review Letters 98, 117007 (2007). G. Li, W. Hu, D. Qian, D. Hsieh, M.Z. Hasan, E. Morosan, R.J. Cava, N.L. Wang Evidence for an Overhauser phase –a semimetal-to-semimetal CDW transition in the parent compound of CuxTiSe2 Physical Review Letters 99, 027404 (2007). L. Wray, D. Qian, D. Hsieh, Y. Xia, H. Eisaki, and M. Z. Hasan Dispersive Collective Charge Modes in an incommensurately modulated cuprate Mott insulator Physical Review B 76, 100507 (2007). D. Qian, L. Wray, D. Hsieh, L. Viciu, R.J. Cava, J.L. Luo, D. Wu, N.L. Wang, and M.Z. Hasan Complete d-Band dispersion relation and small Fermion scale in NaxCoO2 Physical Review Letters 97, 186405 (2006). 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 Low-lying quasiparticle modes and hidden collective charge instabilities in parent cobaltates superconductors NaxCoO2 Physical Review Letters 96, 216405 (2006). 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 Quasiparticle’s quantum coherence and dynamics in the vicinity of metal-insulator phase transition in NaxCoO2 Physical Review Letters 96, 046407 (2006). 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 Fermi surface topology and quasiparticle dynamics of host NaxCoO2 investigated by ARPES Physical Review Letters 92, 246402 (2004). with J.E. Kohn, I.S. Millett, J. Jacob, et al. Random-coil behavior and the dimensions of chemically unfolded proteins: A view with X-ray forward scattering Proc. of the Nat. Acad. of Sci, 101, 12491 (2004). M.Z. Hasan, P.A. Montano, E.D. Isaacs, Z.X. Shen, S. Sinha, Z. Islam, H. Eisaki, N. Motoyama and S. Uchida Momentum-resolved Charge Modes (Holons) in a Prototype 1-D Mott Insulator Studied by Inelastic X-ray Scattering Physical Review Letters 88, 177403 (2002). M.Z. Hasan, E.D. Isaacs, Z.X. Shen, L.L. Miller, K. Tsutsui, T. Tohyama and S. Maekawa Electronic Structure of Mott Insulators Studied by Inelastic X-ray Scattering Science 288, 1811 (2000). with R. Reininger, Y,-D. Chuang et al. Instrumentation: Beamline & Spectrometer Development MERLIN — A meV Resolution Beamline at the ALS Am. Inst. of Phys: Conf. Proc. 879, 509 (2007).