Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field

Zhao, Chuan; Norden, Tenzin; Zhang, Peiyao; Zhao, Puqin; Cheng, Yingchun; Sun, Fan; Parry, James P.; Taheri, Payam; Wang, Jieqiong; Yang, Yihang; Scrace, Thomas; Kang, Kaifei; Yang, Sen; Miao, Guo Xing; Sabirianov, Renat; Κιοσέογλου, Γ.; Huang, Wei; Petrou, A.; Zeng, Hao

doi:10.1038/nnano.2017.68

Cited by 423 publications

(375 citation statements)

References 38 publications

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“…The valley Zeeman term is the valley counterpart of the spin Zeeman but considering only the z-Pauli matrix acting on the valley. This is motivated by [7] and recent experiments [47,48],…”

Section: Basic Definitionsmentioning

confidence: 97%

Effective theory of monolayer TMDC double quantum dots

2018

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Monolayer Transition Metal Dichalcogenides (TMDCs) are promising candidates for quantum technologies, such as quantum dots, because they are truly two-dimensional semiconductors with a direct band gap. In this work, we analyse theoretically the behaviour of a double quantum dot (DQD) system created in the conduction band of these materials, with two electrons in the (1,1) charge configuration. Motivated by recent experimental progress, we consider several scenarios, including different spin-orbit splittings in the two dots and including the case when the valley degeneracy is lifted due to an insulating ferromagnetic substrate. Finally, we discuss in which cases it is possible to reduce the low energy subspace to the lowest Kramers pairs. We find that in this case the low energy model is formally identical to the Heisenberg exchange Hamiltonian.

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“…The valley Zeeman term is the valley counterpart of the spin Zeeman but considering only the z-Pauli matrix acting on the valley. This is motivated by [7] and recent experiments [47,48],…”

Section: Basic Definitionsmentioning

confidence: 97%

Effective theory of monolayer TMDC double quantum dots

2018

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“…[12,20] Herewith, the direction of magnetic moments in YMnO 3 cannot be switched by an electric field because of its weak magnetoelectric coupling and the zero magnetic moment of Y. [12,20] Herewith, the direction of magnetic moments in YMnO 3 cannot be switched by an electric field because of its weak magnetoelectric coupling and the zero magnetic moment of Y.…”

Section: Vallytronicsmentioning

confidence: 99%

“…[14,15] Previous results show that the valley splitting can be switched by a magnetic field. [20] A valley splitting of 2.5 meV T −1 has been achieved in monolayer WSe 2 deposited on a ferromagnetic EuS substrate. [20] A valley splitting of 2.5 meV T −1 has been achieved in monolayer WSe 2 deposited on a ferromagnetic EuS substrate.…”

mentioning

confidence: 94%

“…[20] A valley splitting of 2.5 meV T −1 has been achieved in monolayer WSe 2 deposited on a ferromagnetic EuS substrate. [20] However, the electrical control on the spin and valley transport is more desirable and practical for valleytronic applications. [20] However, the electrical control on the spin and valley transport is more desirable and practical for valleytronic applications.…”

mentioning

confidence: 94%

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Ferroelectricity Tailored Valley Splitting in Monolayer WTe₂/YMnO₃ Heterostructures: A Route toward Electrically Controlled Valleytronics

Song

Wang

2017

Adv Elect Materials

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polarized quantum states, (2) controllably switching between different states, and (3) detecting the states themselves. Many strategies have been proposed to lift the valley degeneracy, such as optical pumping, [10,11] magnetic doping, [12,13] and proximity. [14,15] Previous results show that the valley splitting can be switched by a magnetic field. [16][17][18][19] Recently, a remarkable progress has been made in utilizing the interfacial exchange field to enhance the magnetic control on valley splitting. [20] A valley splitting of 2.5 meV T −1 has been achieved in monolayer WSe 2 deposited on a ferromagnetic EuS substrate. [20] The modulation is an order of magnitude higher than the traditional 0.2 meV T −1 . [20] However, the electrical control on the spin and valley transport is more desirable and practical for valleytronic applications. Multiferroic materials provide a fertile background to control one degree of freedom through the other. [21] Since it is still an open question whether the coupling between valley and ferroelectricity is realizable in a specific system, the electronic properties of monolayer WTe 2 on multiferroic YMnO 3 are investigated. It is found that the coupling appears between valley and ferroelectricity. For a valley-polarized monolayer, a valley splitting of 36 meV is altered when the polarization of the multiferroic substrate is reversed. The spontaneous ferroelectric polarization that can be switched by an electric field shows potential in the electrical control on valley degree of freedom. Considering different multiferroic materials and the artificial design of improper ferroelectrics, [22,23] we further argue that the multiferroic intermediate is an innovating approach toward the electrical control on valley degree, which is a superior approach than the traditional magnetic one.According to previous results, [24] the depolarization field in proper ferroelectric films, for example, BaTiO 3 or PbTiO 3 , strongly suppresses the tendency toward single-domain ferroelectric state, especially in its ultrathin case. Contrary to the proper ones, the improper ferroelectrics like YMnO 3 do not present a critical thickness below which the ferroelectricity disappears. The spontaneous polarization persists in an isolated slab of YMnO 3 . Its value is comparable to that in bulk. So it would be advantageous to consider YMnO 3 substrate and investigate the coupling between valley and ferroelectricity.Hexagonal YMnO 3 with a space group of P6 3 cm has an improper ferroelectricity. [25] Its ferroelectric Curie temperature is about 880 K, [26] much higher than its Néel temperature Control of valley degree of freedom in monolayer transition-metal dichalcogenide (TMDC) has been realized by using optical pumping and magnetic fields. However, an electrical approach is missing and has potential for practical applications. In this paper, valley/ferroelectricity coupling is demonstrated for the first time in a monolayer WTe 2 /YMnO 3 heterostructure. Tunable valley splitting by an electric field is predict...

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“…[3,17] In addition, for most TMDs, the inversion symmetry is naturally broken as a result of odd layer numbers or distorted crystal structure, combined with strong spin-orbit coupling within the layers, to give rise to valley-contrasting optical selection rule, leading to TMDs as ideal materials for valley-and spin-electronics. [18][19][20][21][22][23][24][25][26][27][28][29] The unique orbital hybrid structure between transition metal atoms and chalcogenide atoms endows TMDs with special properties under quantum states or ultra-low temperature conditions, superconductivity, [24,[30][31][32] topological insulators, [33][34][35][36] nonsaturated magnetoresistance, [23,[37][38][39][40][41] ferromagnetism and anti-ferromagnetism, [42] have trigged many research thrust. Moreover, TMDs are compatible with current fabrication technologies, integration with waveguides, resonance cavities to utilize nonlinear optical phenomenon or output nanolaser, or integration with meta-surfaces, plasmon to realize special function are very promising based on TMDs.…”

Section: Introductionmentioning

confidence: 99%

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

Tong¹,

Liu²,

Renli³

et al. 2017

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The layered structure of transition metal dichalcogenides (TMDs) gives rise to many novel properties for functional applications in a wide range of fields. However, successful synthesis of TMDs and directly modulating properties of TMDs during the growth process are facing great challenges, which limits their future practical applications. In this review, we focus on current state of the art chemical vapor deposition (CVD) synthesis of TMDs alloys, convenient methods to modulate properties of TMDs by CVD. Then, TMDs-based lateral and vertical heterostructures utilizing CVD methods are reviewed. Finally, we summarize patterned growth of TMDs briefly.

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Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field

Cited by 423 publications

References 38 publications

Effective theory of monolayer TMDC double quantum dots

Effective theory of monolayer TMDC double quantum dots

Ferroelectricity Tailored Valley Splitting in Monolayer WTe₂/YMnO₃ Heterostructures: A Route toward Electrically Controlled Valleytronics

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

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Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field

Cited by 423 publications

References 38 publications

Effective theory of monolayer TMDC double quantum dots

Effective theory of monolayer TMDC double quantum dots

Ferroelectricity Tailored Valley Splitting in Monolayer WTe2/YMnO3 Heterostructures: A Route toward Electrically Controlled Valleytronics

Growth of Transition Metal Dichalcogenides and Directly Modulating Their Properties by Chemical Vapor Deposition

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Ferroelectricity Tailored Valley Splitting in Monolayer WTe₂/YMnO₃ Heterostructures: A Route toward Electrically Controlled Valleytronics