title: Chiral orbital-angular momentum in the surface states of Bi2Se3.
abstract: 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.
authors.affiliation: Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea.
authors.forename: Seung Ryong
authors.initials: SR
authors.lastname: Park
authors.forename: Jinhee
authors.initials: J
authors.lastname: Han
authors.forename: Chul
authors.initials: C
authors.lastname: Kim
authors.forename: Yoon Young
authors.initials: YY
authors.lastname: Koh
authors.forename: Changyoung
authors.initials: C
authors.lastname: Kim
authors.forename: Hyungjun
authors.initials: H
authors.lastname: Lee
authors.forename: Hyoung Joon
authors.initials: HJ
authors.lastname: Choi
authors.forename: Jung Hoon
authors.initials: JH
authors.lastname: Han
authors.forename: Kyung Dong
authors.initials: KD
authors.lastname: Lee
authors.forename: Nam Jung
authors.initials: NJ
authors.lastname: Hur
authors.forename: Masashi
authors.initials: M
authors.lastname: Arita
authors.forename: Kenya
authors.initials: K
authors.lastname: Shimada
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Namatame
authors.forename: Masaki
authors.initials: M
authors.lastname: Taniguchi