Angle-Resolved Photoelectron Spectroscopy (ARPES); Solid State Physics; Time-and Angle-Resolved Photoelectron Spectroscopy; Topological Insulators; Collective Excitations in Correlated Materials; Charge Density Wave Systems; Femtosecond Laser Pulses; Novel Quantum Materials
D. Leuenberger, J. A. Sobota, S.-L. Yang, A. F. Kemper, P. Giraldo-Gallo, R. G. Moore, I. R. Fisher, P. S. Kirchmann, T. P. Devereaux, Z.-X. Shen (2015), Classification of Collective Modes in a Charge Density Wave by Momentum-Dependent Modulation of the Electronic Band Structure, in Physical Review B
, 91, 201106(R).
S. Gerber, K. W. Kim, Y. Zhang, D. Zhu, N. Plonka, M. Yi, G. L. Dakowski, D. Leuenberger, P. S. Kirchmann, R. G. Moore, M. Chollet, J. M. Glowina, Y. Feng, J.-S. Lee, A. Metha, A. F. Kemper, T. Wolf, Y.-D. Chuang, Z. Hussain, C.-C. Kao, B. Moritz, Z.-X. Shen, T. P. Devereaux, W. S. Lee (2015), Direct characterization of photo-induced lattice dynamics in BaFe2As2, in Nature Communications
Shuolong Yang, Jonathan A. Sobota, Dominik Leuenberger, Alexander F. Kemper, James J. Lee, Felix T. Schmitt, Wei Li, Rob G. Moore, Patrick S. Kirchmann, Zhi-Xun Shen (2015), Thickness-Dependent Coherent Phonon Frequency in Ultrathin FeSe/ SrTiO3 Films, in Nano Letters
, DOI: 10.10.
Sobota J. A., Yang S. -L., Leuenberger D., Kemper A. F., Analytis J. G., Fisher I. R., Kirchmann P. S., Devereaux T. P., Shen Z. -X. (2014), Distinguishing Bulk and Surface Electron-Phonon Coupling in the Topological Insulator Bi2Se3 Using Time-Resolved Photoemission Spectroscopy, in PHYSICAL REVIEW LETTERS
, 113(15), 157401-1-157401-5.
Sobota J. A., Yang S. -L., Leuenberger D., Kemper A. F., Analytis J. G., Fisher I. R., Kirchmann P. S., Devereaux T. P., Shen Z. -X. (2014), Ultrafast electron dynamics in the topological insulator Bi2Se3 studied by time-resolved photoemission spectroscopy, in JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA
, 195, 249-257.
S. Yang, J. A. Sobota, D. Leuenberger, Y. He, M. Hashimoto, D. H. Lu, H. Eisaki, P. S. Kirchmann, Z.-X. Shen, Inequivalence of Single-Particle and Population Lifetimes in a Cuprate Superconductor, in Physical Review Letters
The search for materials with novel electronic properties is an important topic within condensed matter physics. The novel quantum material class of topological insulators reveal the existence of metallic surface states at the boundary of the insulating crystal. Due to strong spin-orbit interaction, the spin and momentum of the electrons in these states are intimately coupled, which provides channels to drive spin-polarized currents at the surface. Understanding how excited electrons in these spin-textured surface states scatter with electrons in surface and bulk states as well as other quasi-particles excitations is crucial for the design of future spintronic devices. Femtosecond time- and angle-resolved photoelectron spectroscopy (trARPES) is currently developing into a profound tool for material science and offers the opportunity to investigate these electron-electron scattering processes in topological insulators directly in the time-domain.In another class of materials, the Charge Density Wave (CDW) systems, strong electron-phonon coupling connects periodic lattice distortions with an electronic metal-to-insulator phase transition. Despite the fact, that trARPES allows for ultrafast excitation and subsequent monitoring of collective modes, still little is known about the coupling strength of the distinct modes in these prototypical CDW materials.The project proposed here will investigate the non-equilibrium electronic structure and corresponding scattering processes on thin films of the topological insulator Bi2Se3 and on RTe3 CDW systems by means of trARPES experiments. This will bring new insight into the scattering rates of non-equilibrium electronic populations in topological insulators as well as into the coupling strength between distinct collective excitations in CDW systems, respectively. The experiments will be performed in the group of Prof. Z.-X. Shen at the Geballe Laboratory for Advanced Materials at Stanford University, offering a combination between photoemission experiment, material growth and theory.