Changyoung Kim — Page 5

arXiv2011

Chiral orbital-angular-momentum in the surface states of Bi2Se3

Locking of the spin of a quasi-particle to its momentum in split bands of on the surfaces of metals and topological insulators (TIs) is understood in terms of Rashba effect where a free electron in the surface states feels an effective magnetic field. On the other hand, the orbital part of the angular momentum (OAM) is usually neglected. We performed angle resolved photoemission experiments with circularly polarized lights and first principles density functional calculation with spin-orbit coupling on a TI, Bi2Se3, to study the local OAM of the surface states. We show from the results that OAM in the surface states of Bi2Se3 is significant and locked to the electron momentum in opposite direction to the spin, forming chiral OAM states. Our finding opens a new possibility to have strong light-induced spin-polarized current in the surface states.

cond-mat.mtrl-sci↗

arXiv2003

Resonant Inelastic X-Ray Scattering (RIXS) in SrCuO$_{2}$

The resonant inelastic x-ray scattering (RIXS) was measured in an insulating SrCuO$_{2}$ with changing the incident photon energy ($hν$) near the Cu $1s$ absorption edge (K-edge). Complex structures and their dependences on the momentum transfer($Δk$) and $hν$ were observed. The $hν$ dependence of the RIXS spectra measured for a constant $Δk$=2.4$π$ has shown a remarkable enhancement near the absorption maximum and a shift of the spectral weight toward larger loss-energy with increasing $hν$. Also, the energy of the inelastic loss peak in the RIXS spectra for the fixed excitation at 8.993 keV, 10 eV below the absorption maximum, has shown a clear dependence on $Δk$. These results are in a qualitative agreement with a theoretical prediction. Full utilization of the potential of the high brilliance X ray light source at BL19LXU of SPring-8 with 27 m long insertion device will open up a breakthrough in RIXS for heavy transition metal compounds in accordance with the improvement in focussing and analyzing elements.

cond-mat.str-el↗