Spin-polarization and spin-flip through a monolayer MoS 2 superlattice via the Rashba effect
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Spin‑polarization and spin‑flip through a monolayer MoS2 superlattice via the Rashba effect Farhad Tavakoli1 · Edris Faizabadi2 · Seyed Mohammad Elahi1 · Mohammadreza Hantehzadeh1 Received: 4 March 2020 / Accepted: 25 October 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract The spin-resolved transport for monolayer MoS2 through a zigzag nanoribbon superlattice based on the transfer matrix method in the resonant tunneling regime is investigated in the presence of an external perpendicular electric field. The controllable external electric field leads to the so-called Rashba effect, which can modulate the internal spin–orbit coupling. Our investigations show that by controlling the Rashba strength, it is possible to attain 100% spin-polarization and spin-flip, which can be used in designing an optimized spintronic device. In addition, the effects of superlattice specific parameters (D/W), the barrier height (V0), and the number of barriers (N) on the functionality of the system are studied, leading to optimum results for the case of 20 barriers. Keywords Spin-resolved transport · Rashba effect · Monolayer MoS2 · Zigzag nanoribbon · Superlattice
1 Introduction Nowadays, monolayer MoS2 (ML-MoS2) is a favorite twodimensional transition metal dichalcogenide (TMD), which due to its strong optical excitation and tunable spin-valley polarization is a suitable candidate for constructing integrated spintronic circuits at room temperature [1–4]. Its electronic valence band is split into two spin-up and spin-down bands, which is suitable for applications in spintronics and valleytronics [5–9]. Li et al. [10] demonstrated that zigzag MoS2 nanoribbons show magnetic and metallic behaviors, while armchair nanoribbons exhibit nonmagnetic and semiconductor properties. In another study, Kou et al. demonstrated that zigzag nanoribbons are more stable and sensitive to an external electric field [11, 12]. Since spin–orbit coupling (SOC) is a relativistic effect, both an internal electric field due to the lattice and an external field due to a bias generate an effective magnetic field on a moving electron, which produces SOC and defines a new degree of freedom in terms of the spin. These phenomena are recognized as the intrinsic * Edris Faizabadi [email protected] 1
Department of Physics, Science and Research Branch, Islamic Azad University, 1477893855 Tehran, Iran
School of Physics, Iran University of Science and Technology, 1684613114 Tehran, Iran
2
spin Hall effect and the Rashba–Edelstein effect, respectively [13–18]. When an electron moves in an external electric field, say E = Ez, z experiences a magnetic field which introduces a momentum-dependent spin–orbit ( ) coupling, the so-called Rashba coupling of Ĥ R = 𝜆R ∕� (𝐳 × 𝐩) ⋅ 𝛔 , where λR is called the Rashba parameter [19–24]. This kind of interaction allows us to remove spin degeneracy without applying an external magnetic field. Caviglia et al. used it to introduce a spintronic field-effect transistor [25, 26]. ML-MoS2, as a
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