Chiral Orbital-Angular Momentum in the Surface States of Bi2Se3

Park Seung Ryong

Han Jinhee

Kim Chul

Koh Yoon Young

Kim Changyoung

Lee Hyungjun

Choi Hyoung Joon

Han Jung Hoon

Lee Kyung Dong

Hur Nam Jung

Arita Masashi

Shimada Kenya

Namatame Hirofumi

Taniguchi Masaki

Physical Review Letters

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.

Physics [ 420 ]

eng

American Physical Society

(c) 2012 American Physical Society

[ISSN] 0031-9007

[DOI] 10.1103/PhysRevLett.108.046805

[NCID] AA00773679

[DOI] http://dx.doi.org/10.1103/PhysRevLett.108.046805