Giant and tunable valley degeneracy splitting inMoTe2

Abstract

Valleys in monolayer transition-metal dichalcogenides seamlessly connect two basic carriers of quantum information, the electron spin and photon helicity. Lifting the valley degeneracy is an attractive route to achieve further optelectronic manipulations. However, magnetic field only creates a very small valley splitting. We propose a strategy to create giant valley splitting by proximityinduced Zeeman effect. Our first principles calculations of monolayer MoTe2 on a EuO substrate show that valley splitting over 300 meV can be generated. Interband transition energies become valley dependent, leading to selective spin-photon coupling by optical frequency tuning. The valley splitting is also continuously tunable by rotating the substrate magnetization. The giant and tunable valley splitting adds a new dimension to the exploration of novel optoelectronic devices based on magneto-optical coupling and magnetoelectric coupling. Introduction.-In many kinds of transition-metal dichalcogenide monolayers, a pair of degenerate valleys in the band structure give rise to novel valley-contrasting physics and potential applications. Electrons with a definite spin can be selectively excited by photons with a given helicity through the valleys, thereby furnishing a unique interface between the two elementary carriers of quantum information.1-4 . Valley Hall effect has also been observed recently, enabling electrical detection and manipulation of the photocurrent 5 . Furthermore, electronic states also possess valley-dependent orbital magnetic moments, which, together with the spin magnetic moment, provide the opportunities for magnetic control of the valleys and multiple electronic/optoelectronic functionalities based on magnetic effects.

Electrically tunable polarizer based on 2D orthorhombic ferrovalley materials

“…Very recently, Tong et.al [12] introduced the concept of ferrovalley material in transition metal dichalcogenides. Compared with valley degeneracy splitting through external means [13][14][15][16][17], the valley polarization in the proposed ferrovalley monolayers, originating from ferromagnetism, is spontaneous. It is, thus, of great importance in paving the way to the practical use of valleytronics in a nonvolatile way.…”

Nonlocal transistor based on pure crossed Andreev reflection in a EuO-graphene/superconductor hybrid structure

“…One major challenge to observe the rapid G CAR oscillation is the fabrication of a high-quality sample as the interface roughness and Fermi level fluctuations can wash out the oscillation. Finally, we point out that the pCAR mechanism proposed here is universally applicable to systems with similar band topology such as YiG-graphene [43] and monolayer transition-metal dichalcogenides with magnetic doping [44] or with proximity to EuO [45]. These structures offer alternative platforms to test the validity of our prediction.…”

Effect of intervalley interaction on band topology of commensurate graphene/EuO heterostructures

“…Recently, graphene was successfully deposited on an atomically thin-film insulating ferrimagnet, yttrium iron garnet (YIG), and the transport measurements revealed an unquantized anomalous Hall effect due to proximity induced ferromagnetism 12 . Several other magnetic material/van der Waals (vdW) materials combinations (for example graphene/EuO, graphene/BiFeO 3 and MoTe 2 /EuO 8,13-15 ) have been proposed for possible spintronics 13,14 and valleytronics 15 applications. In these systems, ferromagnetic ordering is induced by a proximity effect.…”