Department of Applied Physics

Description

Condensed Matter Physics

Quantum many-body physics in strongly-correlated electron and other novel quantum systems. Examples include high-temperature superconductors, Fe-pnictide superconductors, topological quantum matter, density wave materials, quantum system with constrained dimension - monolayer superconductivity and transition metal dichalcogeneides. The main tool is high resolution angle-resolved photo-emission spectroscopy, but other photon based tools are also used, such as resonance x-ray scattering, inelastic x-ray scattering and microwave impedance microscopy.

Lasers and Accelerators

Develop and optimize synchrotron radiation based photoemission experiments - both spin integrated and spin resolved spectroscopy. Development of laser capabilities to enable condensed matter physics experiments---examples include time resolved photo-emission spectroscopy using UV lasers and soft x-ray scattering using the LCLS.

Nanoscience and Quantum Engineering

Devepment of AFM-based near field microwave microscopy that enables measurement of electrical properties with 50nm or better resolution--- to study physics and material science problems of mesoscopic length scale, such as metal-insulator transition with mesoscale inhomogeneity, and quantum hall edge physics. Investigation of the physics and applications of diamondoids and related materials, where the combination of diamond structure and nm length scale gives rise to unique properties. Use of nanostructured material and devices to realize the goal of photon enhanced thermionic emission for concentrator solar conversion.

Courses Taught

• X-Ray and VUV Physics
• Solid State Physics and the Energy Challenge

Selected Publications

• Discovery of a single topological Dirac fermion in the strong inversion asymmetric compound BiTeCl
• Direct observation of the transition from indirect to direct bandgap in atomically thin epitaxial MoSe2
• Discovery of a Three-Dimensional Topological Dirac Semimetal, Na3Bi
• Energy gaps in high-transition-temperature cuprate superconductors
• Interfacial mode coupling as the origin of the enhancement of T-c in FeSe films on SrTiO3
• Direct spectroscopic evidence for phase competition between the pseudogap and superconductivity in Bi2Sr2CaCu2O8+delta
• A Stable Three-dimensional Topological Dirac Semimetal Cd3As2
• Photon Enhanced Thermionic Emission (PETE) for Solar Concentrator Systems
• A Pressure Tuned Insulator-To-Metal Critical Point in the Copper Oxides
• Momentum Resolved Charge Excitations in a One-Dimensional Prototype Mott Insulator
• Massive Dirac Fermion on the Surface of Topological Insulator with Magnetic Dopants
• Band structure and Fermi surface of electron-doped C60 monolayers
• Fermi Surfaces, Surface States, and Surface Reconstruction in Sr2RuO4
• Abrupt Onset of Second Energy Gap at Superconducting Transition along the Fermi Arc of Underdoped Bi2212
• Distinct Fermi-momentum dependent energy gaps in deeply underdoped Bi2212
• Doping Dependence of n-Type Superconductors Investigated by ARPES
• Strong Electron-Phonon Coupling in High-Tc Superconductors
• Mesoscopic Percolation Resistance Network in a Strained Manganite Thin Film
• Effect of the Amplitude Mode and the Transient Melting of the Charge Density Wave on the Electronic Structure of TbTe3
• Unusual Electron Emission from Self-Assembled Monolayers of Functionalized Diamondoids
• Nodal Electrons Do Not Need A Superconductor: The Polaronic Metal in Layered Colossal Magnetoresistive Manganites
• Large Gap Topological Insulator Bi2Te3 with a Single Dirac Cone on the Surface
• Electronic Structure of LaOFeP – a different type of superconductor
• Anomalous spectral evolution upon the opening of pseudogap in a high-Tc copper oxide
• Excitation Gap in the Normal State of Underdoped Bi2Sr2CaCu2O8+d
• Anomalously Large Gap Anisotropy in the a-b plane of Bi2212
• Angle-resolved photoemission spectroscopy of the curpate superconductors