Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach
Van der Waals heterostructures assembled from atomically thin crystals are ideal model systems to study spin-orbital coupled transport because they exhibit a strong interplay between spin, lattice, and valley degrees of freedom that can be manipulated by strain, electric bias, and proximity effects....
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
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American Physical Society
2021-08-01
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| Series: | Physical Review Research |
| Online Access: | http://doi.org/10.1103/PhysRevResearch.3.033137 |
| _version_ | 1797210936904253440 |
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| author | Carmen Monaco Aires Ferreira Roberto Raimondi |
| author_facet | Carmen Monaco Aires Ferreira Roberto Raimondi |
| author_sort | Carmen Monaco |
| collection | DOAJ |
| description | Van der Waals heterostructures assembled from atomically thin crystals are ideal model systems to study spin-orbital coupled transport because they exhibit a strong interplay between spin, lattice, and valley degrees of freedom that can be manipulated by strain, electric bias, and proximity effects. The recently predicted spin-helical regime in graphene on transition metal dichalcogenides, in which spin and pseudospin degrees of freedom are locked together [Offidani et al., Phys. Rev. Lett. 119, 196801 (2017)PRLTAO0031-900710.1103/PhysRevLett.119.196801] suggests their potential application in spintronics. Here, by deriving an Eilenberger equation for the quasiclassical Green's function of two-dimensional Dirac fermions in the presence of spin-orbit coupling (SOC) and scalar disorder, we obtain analytical expressions for the dc spin galvanic susceptibility and spin Hall conductivity in the spin-helical regime. Our results disclose a sign change in the spin Hall angle (SHA) when the Fermi energy relative to the Dirac point matches the Bychkov-Rashba energy scale, irrespective of the magnitude of the spin-valley interaction imprinted on the graphene layer. The behavior of the SHA is connected to a reversal of the total internal angular momentum of Bloch electrons that reflects the spin-pseudospin entanglement induced by SOC. We also show that the charge-to-spin conversion efficiency reaches a maximum when the Fermi level lies at the edge of the spin-minority band in agreement with previous findings. Both features are fingerprints of spin-helical Dirac fermions and suggest a direct way to estimate the strength of proximity-induced SOC from transport data. The relevance of these findings for interpreting recent spin-charge conversion measurements in nonlocal spin-valve geometry is also discussed. |
| first_indexed | 2024-04-24T10:18:31Z |
| format | Article |
| id | doaj.art-80f78b3ab5484f56a02dd13cf88c9801 |
| institution | Directory Open Access Journal |
| issn | 2643-1564 |
| language | English |
| last_indexed | 2024-04-24T10:18:31Z |
| publishDate | 2021-08-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review Research |
| spelling | doaj.art-80f78b3ab5484f56a02dd13cf88c98012024-04-12T17:12:44ZengAmerican Physical SocietyPhysical Review Research2643-15642021-08-013303313710.1103/PhysRevResearch.3.033137Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approachCarmen MonacoAires FerreiraRoberto RaimondiVan der Waals heterostructures assembled from atomically thin crystals are ideal model systems to study spin-orbital coupled transport because they exhibit a strong interplay between spin, lattice, and valley degrees of freedom that can be manipulated by strain, electric bias, and proximity effects. The recently predicted spin-helical regime in graphene on transition metal dichalcogenides, in which spin and pseudospin degrees of freedom are locked together [Offidani et al., Phys. Rev. Lett. 119, 196801 (2017)PRLTAO0031-900710.1103/PhysRevLett.119.196801] suggests their potential application in spintronics. Here, by deriving an Eilenberger equation for the quasiclassical Green's function of two-dimensional Dirac fermions in the presence of spin-orbit coupling (SOC) and scalar disorder, we obtain analytical expressions for the dc spin galvanic susceptibility and spin Hall conductivity in the spin-helical regime. Our results disclose a sign change in the spin Hall angle (SHA) when the Fermi energy relative to the Dirac point matches the Bychkov-Rashba energy scale, irrespective of the magnitude of the spin-valley interaction imprinted on the graphene layer. The behavior of the SHA is connected to a reversal of the total internal angular momentum of Bloch electrons that reflects the spin-pseudospin entanglement induced by SOC. We also show that the charge-to-spin conversion efficiency reaches a maximum when the Fermi level lies at the edge of the spin-minority band in agreement with previous findings. Both features are fingerprints of spin-helical Dirac fermions and suggest a direct way to estimate the strength of proximity-induced SOC from transport data. The relevance of these findings for interpreting recent spin-charge conversion measurements in nonlocal spin-valve geometry is also discussed.http://doi.org/10.1103/PhysRevResearch.3.033137 |
| spellingShingle | Carmen Monaco Aires Ferreira Roberto Raimondi Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach Physical Review Research |
| title | Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach |
| title_full | Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach |
| title_fullStr | Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach |
| title_full_unstemmed | Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach |
| title_short | Spin Hall and inverse spin galvanic effects in graphene with strong interfacial spin-orbit coupling: A quasi-classical Green's function approach |
| title_sort | spin hall and inverse spin galvanic effects in graphene with strong interfacial spin orbit coupling a quasi classical green s function approach |
| url | http://doi.org/10.1103/PhysRevResearch.3.033137 |
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