Woojin Jung

Quasiparticle scattering and the protected nature of the topological states in a parent topological insulator Bi 2 Se 3

We report on angle resolved photoemission spectroscopic studies on a parent topological insulator (TI), Bi

Time-resolved energy transduction in a quantum capacitor

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Trapping-Mediated Chemisorption of Ethylene on Si(001)-c(4 x 2)

Se

Photoemission studies of Cu intercalated NbSe2

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Scanning tunneling microscopy of oxygen‐induced two‐state oscillators on Si(111)‐7×7

. The line width of the spectral function (inverse of the quasi-particle lifetime) of the topological metallic (TM) states shows an anomalous behavior. This behavior can be reasonably accounted for by assuming decay of the quasi-particles predominantly into bulk electronic states through electron-electron interaction and defect scattering. Studies on aged surfaces reveal that topological metallic states are very much unaffected by the potentials created by adsorbed atoms or molecules on the surface, indicating that topological states could be indeed protected against weak perturbations.

Electronic Structure Studies of Detwinned BaFe2As2 by Photoemission

The capability to deposit charge and energy quantum-by-quantum into a specific atomic site could lead to many previously unidentified applications. Here we report on the quantum capacitor formed by a strongly localized field possessing such capability. We investigated the charging dynamics of such a capacitor by using the unique scanning tunneling microscopy that combines nanosecond temporal and subangstrom spatial resolutions, and by using Si(001) as the electrode as well as the detector for excitations produced by the charging transitions. We show that sudden switching of a localized field induces a transiently empty quantum dot at the surface and that the dot acts as a tunable excitation source with subangstrom site selectivity. The timescale in the deexcitation of the dot suggests the formation of long-lived, excited states. Our study illustrates that a quantum capacitor has serious implications not only for the bottom-up nanotechnology but also for future switching devices.