Topological Insulators; Time-and Angle-Resolved Photoelectron Spectroscopy; Charge Density Wave Systems; Novel Quantum Materials; Collective Excitations in Correlated Materials; Solid State Physics; Angle-Resolved Photoelectron Spectroscopy (ARPES); Femtosecond Laser Pulses
Y. L. Chen M. Kanou Z. K. Liu H. J. Zhang J. A. Sobota D. Leuenberger S. K. Mo B. Zhou, S-L. Yang P. S. Kirchmann D. H. Lu R. G. Moore Z. Hussain Z. X. Shen X. L. Qi T. Sasagawa (2013), Discovery of a Single Topological Dirac Fermion in a Strong Inversion Asymmetric Compound BiTeCl, in Nature Physics
, 9, 704-708.
J. A. Sobota S.-L. Yang D. Leuenberger A. F. Kemper J. G. Analytis I. R. Fisher, P. S. Kirchmann T. P. Devereaux and Z.-X. Shen, Ultrafast electron dynamics in the topological insulator Bi2Se3 studied by time-resolved photoemission spectroscopy, in Journal of Electron Spectroscopy and Related Phenomena
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, what provides channels to drive spin-polarized currents at the solid surface. Understanding how excited electrons in these spin-textured surface states scatter with electrons and other quasi-particles is crucial for the design of future spintronic devices. Femtosecond time- and angle-resolved photoelectron spectroscopy (trARPES) is currently developing rapidly 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 strongly correlated 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 the ultrafast excitation and subsequent monitoring of collective modes close to that phase transition, still little is known about the mutual coupling strength of the distinct modes in these CDW materials.The project proposed here aims to investigate the non-equilibrium electronic structure and corresponding scattering processes on thin and (magnetically) doped films of the topological insulator Bi2Se3 and on RTe3 CDW systems by means of trARPES experiments. This is expected to bring new insight into the scattering rates of persistent non-equilibrium electronic populations in topological insulators as well as into the mutual coupling strength between distinct collective excitations in CDW systems, respectively. The experiments will be performed in Prof. Z.-X. Shen’s group at the Geballe Laboratory for Advanced Materials at Stanford University, offering a combination between photoemission experiment, material growth and theory.