Zeeman-type spin splitting controlled by an electric field

Yuan, Huatang; Bahramy, M. S.; Morimoto, Keiko; Wu, Sanfeng; Nomura, Kentaro; Yang, Bohm Jung; Shimotani, Hidekazu; Suzuki, Ryuji; Toh, Matthias Paul Han Sim; Kloc, Christian; Xu, Xiaodong; Arita, Ryotaro; Nagaosa, Naoto; Iwasa, Yoshihiro

doi:10.1038/nphys2691

Cited by 488 publications

(485 citation statements)

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“…These properties have also been actively explored for new electronics and optoelectronics applications [4][5][6][7][8][9][10][11][12][13][14][15] . In the monolayer limit, group-VI TMDs (MX 2 , M = Mo, W; X = S, Se) are direct band-gap semiconductors with the fundamental energy gap located at the K and K' points of the Brillouin zone 16,17 .…”

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Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

et al. 2017

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We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe 2 and MoSe 2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe 2 , and parallel spins in monolayer MoSe 2 . The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first principles calculations. These values also suggest that both n-and ptype WSe 2 and MoSe 2 can be relevant for spin-and valley-based applications.

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Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

et al. 2017

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“…As a result of time reversal symmetry, the spin splitting shows opposite signs between K and K' valleys at equal energies. [5,[10][11][12] Namely, if the band edge at K valley is spin-up state, the band edge at K' valley must be spin-down as illustrated in FIG. 1(a).…”

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Long valley relaxation time of free carriers in monolayer WSe2

Yan

Yang

et al. 2017

Phys. Rev. B

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Monolayer transition metal dichalcogenids (TMDs) feature valley degree of freedom, giant spinorbit coupling and spin-valley locking. These exotic natures stimulate efforts of exploring the potential applications in conceptual spintronics, valleytronics and quantum computing. Among all the exotic directions, a long lifetime of spin and/or valley polarization is critical. The present valley dynamics studies concentrate on the band edge excitons which predominates the optical response due to the enhanced Coulomb interaction in two dimensions. The valley lifetime of free carriers remains in ambiguity. In this work, we use time-resolved Kerr rotation spectroscopy to probe the valley dynamics of excitons and free carriers in monolayer tungsten diselinide. The valley lifetime of free carriers is found around 2 ns at 70 K, about 3 orders of magnitude longer than the excitons of about 2 ps. The extended valley lifetime of free carriers evidences that exchange interaction dominates the valley relaxation in optical excitation. The pump-probe spectroscopy also reveals the exciton binding energy of 0.60 eV in monolayer WSe2.

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“…One may view (∇V (r) × k) ≡ B ef f as an effective magnetic field acting on spinŝ. For monolayer WSe 2 , k is in the 2D plane; E is dominated by an internal electric dipole field [8] (see Fig. 1(a)) thus also in the plane, giving rise to a B ef f largely perpendicular to the plane to orient the spins into a Zeeman like up-down texture [8] in most regions of the BZ.…”

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“…For monolayer WSe 2 , k is in the 2D plane; E is dominated by an internal electric dipole field[8] (see Fig. 1(a)) thus also in the plane, giving rise to a B ef f largely perpendicular to the plane to orient the spins into a Zeeman like up-down texture [8] in most regions of the BZ. For WSe 2 FET, gate voltage adds an additional electric field E ext which is perpendicular to the 2D plane: (E ext × k) is thus oriented inside the plane which attempts to orient the spins into a Rashba like…”

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“…The newest member of such material is the two dimensional (2D) transitionmetal dichalcogenides (TMDC). Since the exfoliation of monolayer TMDC (ML-TMDC) three years ago [1,2], very interesting electronic and optical properties of these materials have been already discovered both experimentally and theoretically [3][4][5][6][7][8]. TMDC is in the form of MX 2 where M denotes heavy elements such as Mo, W, and X denotes S, Se, etc..…”

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Electric control of spin in monolayer WSe₂field effect transistors

et al. 2014

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We report a first principles theoretical investigation of quantum transport in monolayer WSe2 field effect transistor (FET). Due to a strong spin-orbit interaction (SOI) and the atomic structure of the two-dimensional (2D) lattice, monolayer WSe2 has an interesting electronic structure that exhibits Zeeman-like up-down spin texture near the K and K ′ points of the Brillouin zone. In a FET, the gate electric field induces an extra, externally tunable SOI that re-orients the spins into a Rashba-like texture thereby realizing electric control of the spin. Quantum transport is modulated by the spin texture, namely by if the spin orientation of the carrier after the gated channel region, matches or miss-matches that of the FET drain electrode. The carrier current in the FET is labelled both the spin index and the valley index, realizing spintronics and valleytronics in the same device.PACS numbers: 75.70.Tj, 73.25.+i, Electronic materials in reduced dimension have attracted great attention for decades. The newest member of such material is the two dimensional (2D) transitionmetal dichalcogenides (TMDC). Since the exfoliation of monolayer TMDC (ML-TMDC) three years ago[1, 2], very interesting electronic and optical properties of these materials have been already discovered both experimentally and theoretically [3][4][5][6][7][8]. TMDC is in the form of MX 2 where M denotes heavy elements such as Mo, W, and X denotes S, Se, etc.. The most important properties of several ML-TMDC, for instance WSe 2 and MoS 2 , are the direct band gap in the visible frequency range [1,2] and the strong spin-orbit interaction (SOI). ML-TMDC materials have honeycomb lattice shown in Fig. 1(a) and in the momentum space there are two inequivalent valleys at K and K ′ of the first Brillouin zone (BZ, Fig. 1(a)). Due to the well-separation of K from K ′ , it was proposed [4][5][6][7] that the valley index τ = K, K ′ may be used as quantum numbers for valleytronics. At the same time, the strong SOI are fundamentally important for spintronics. Being able to realize both valleytronics and spintronics in a single material is a very exciting new opportunity and ML-TMDC may well be the emerging electronic material for new generations of nanoelectronics. It is the purpose of this work to theoretically investigate fundamental properties of quantum transport in ML-TMDC material WSe 2 in the form of a field effect transistor (FET).In particular, by atomistic first principles analysis we found that the spins in WSe 2 can be well controlled by an external electric field -here by a gate voltage of the FET, and such a control has direct consequences to quantum transport properties of the device. Achieving efficient electric control of spin is a long-sought goal of spintronics [9][10][11][12], for WSe 2 it is due to not only the strong SOI but also to its 2D lattice structure. Conceptually, SOI is proportional toŝ · (∇V (r) × k), where s is the spin and k the momentum of the carrier while E = −∇V (r) the electric field seen by the carrier. One may view ...

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Zeeman-type spin splitting controlled by an electric field

Cited by 488 publications

References 42 publications

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Long valley relaxation time of free carriers in monolayer WSe2

Electric control of spin in monolayer WSe₂field effect transistors

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Zeeman-type spin splitting controlled by an electric field

Cited by 488 publications

References 42 publications

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Long valley relaxation time of free carriers in monolayer WSe2

Electric control of spin in monolayer WSe2field effect transistors

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Electric control of spin in monolayer WSe₂field effect transistors