Hyungjun Lee

Chiral Orbital-Angular Momentum in the Surface States of Bi2Se3

We performed angle-resolved photoemission (ARPES) experiments with circularly polarized light and first-principles density functional calculation with spin-orbit coupling to study surface states of a topological insulator Bi2Se3. We observed circular dichroism (CD) as large as 30% in the ARPES data with upper and lower Dirac cones showing opposite signs in CD. The observed CD is attributed to the existence of local orbital-angular momentum (OAM). First-principles calculation shows that OAM in the surface states is significant and is locked to the electron momentum in the opposite direction to the spin, forming chiral OAM states. Our finding opens a new possibility for strong light-induced spin-polarized current in surface states. We also provide a proof for local OAM origin of the CD in ARPES.

Low-velocity anisotropic Dirac fermions on the side surface of topological insulators

We report anisotropic Dirac-cone surface bands on a side-surface geometry of the topological insulator Bi

Single-Impurity Scattering and Carrier Mobility in Doped Ge/Si Core-Shell Nanowires

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Role of d orbitals in the Rashba-type spin splitting for noble-metal surfaces

Se

Time-resolved quasiparticle dynamics of the itinerant antiferromagnet UPtGa5

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Lattice-matched heterojunctions between topological and normal insulators: A first-principles study

revealed by first-principles density-functional calculations. We find that the electron velocity in the side-surface Dirac cone is anisotropically reduced from that in the (111)-surface Dirac cone, and the velocity is not in parallel with the wave vector {\bf k} except for {\bf k} in high-symmetry directions. The size of the electron spin depends on the direction of {\bf k} due to anisotropic variation of the noncollinearity of the electron state. Low-energy effective Hamiltonian is proposed for side-surface Dirac fermions, and its implications are presented including refractive transport phenomena occurring at the edges of tological insulators where different surfaces meet.

Interplay between spin-orbit coupling and crystal-field effect in topological insulators

We report electronic transport properties of doped Ge-core/Si-shell and Si-core/Ge-shell nanowires (NWs) from first-principles. We obtain single-impurity scattering properties of electrons and holes using density-functional methods for quantum conductance and then estimate charge-carrier mobilities considering multiple impurity scatterings. It is found that holes in the Ge-core/Si-shell NW with B-doped Si and electrons in the Si-core/Ge-shell NW with P-doped Ge have higher mobilities than holes and electrons in other chemical and doping configurations. These results reflect asymmetric radial confinements of charge carriers in the core-shell NWs and show that Si-core/Ge-shell NWs with electron donors in the shell are as promising for nanoelectronic devices as Ge-core/Si-shell NWs with electron acceptors in the shell.

Field-induced recovery of massless Dirac fermions in epitaxial graphene on SiC

We investigate the Rashba-type spin splitting in the Shockley surface states on Au(111) and Ag(111) surfaces, based on first-principles calculations. By turning on and off spin-orbit interaction (SOI) partly, we show that although the surface states are mainly of

Plethora of Coexisting Topological Band Degeneracies in Nonsymmorphic Molecular Crystal OsOF

p

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-orbital character with only a small