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Journal Physical Review Letters 121, 186401 (2018)
Title Experimental Observation of Hidden Berry Curvature in Inversion-Symmetric Bulk 2H−WSe2
Author Soohyun Cho, Jin-Hong Park, Jisook Hong, Jongkeun Jung, Beom Seo Kim, Garam Han, Wonshik Kyung, Yeongkwan Kim, S.-K. Mo, J. D. Denlinger, Ji Hoon Shim, Jung Hoon Han, Changyoung Kim, and Seung Ryong Park
We investigate the hidden Berry curvature in bulk 2H-WSe2 by utilizing the surface sensitivity of
angle resolved photoemission (ARPES). The symmetry in the electronic structure of transition metal
dichalcogenides is used to uniquely determine the local orbital angular momentum (OAM) contribution to
the circular dichroism (CD) in ARPES. The extracted CD signals for the K and K0 valleys are almost
identical, but their signs, which should be determined by the valley index, are opposite. In addition, the sign
is found to be the same for the two spin-split bands, indicating that it is independent of spin state. These
observed CD behaviors are what are expected from Berry curvature of a monolayer of WSe2. In order to see
if CD-ARPES is indeed representative of hidden Berry curvature within a layer, we use tight binding
analysis as well as density functional calculation to calculate the Berry curvature and local OAM of a
monolayer WSe2. We find that measured CD-ARPES is approximately proportional to the calculated Berry
curvature as well as local OAM, further supporting our interpretation.