Optically controlled single-valley exciton doublet states with tunable internal spin structures and spin magnetization generation

Journal Article · Tue Jul 25 00:00:00 EDT 2023 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.2307611120· OSTI ID:1992406

Ruan, Jiawei ^[1]; Li, Zhenglu ^[1]; Ong, Chin Shen ^[1]; Louie, Steven G.  ^[1]

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1. Department of Physics, University of California at Berkeley, Berkeley, CA 94720, Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720

Manipulating quantum states through light–matter interactions has been actively pursued in two-dimensional materials research. Significant progress has been made toward the optical control of the valley degrees of freedom in semiconducting monolayer transition-metal dichalcogenides, based on doubly degenerate excitons from their two distinct valleys in reciprocal space. Here, we introduce a type of optically controllable doubly degenerate exciton states that come from a single valley, dubbed as single-valley exciton doublet (SVXD) states. They are unique in that their constituent holes originate from the same valence band, making possible the direct optical control of the spin structure of the excited constituent electrons. Combining ab initio GW plus Bethe–Salpeter equation ( GW -BSE) calculations and a theoretical analysis method, we demonstrate such SVXD in substrate-supported monolayer bismuthene—which has been successfully grown using molecular beam epitaxy. In each of the two distinct valleys in the Brillouin zone, strong spin–orbit coupling and $C_{3v}$ symmetry lead to a pair of degenerate 1s exciton states (the SVXD states) with opposite spin configurations. Any coherent linear combinations of the SVXD in a single valley can be excited by light with a specific polarization, enabling full manipulation of their internal spin configurations. In particular, a controllable net spin magnetization can be generated through light excitation. Our findings open routes to control quantum degrees of freedom, paving the way for applications in spintronics and quantum information science.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE; USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities (SUF); USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); National Science Foundation (NSF)
• Grant/Contract Number: AC02- 05CH11231; AC02-05CH11231; ACI-1053575; OAC1818253
• OSTI ID: 1992406
• Alternate ID(s): OSTI ID: 2281841
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Vol. 120 Journal Issue: 31; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of Sciences
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
excitonic effects
2D materials
first principles
spins