Magnetotransport in heterostructures of transition metal dichalcogenides and graphene

Abstract

We use a van der Waals pickup technique to fabricate different heterostructures containing WSe 2 (WS 2 ) and graphene. The heterostructures were structured by plasma etching, contacted by one-dimensional edge contacts, and a top gate was deposited. For graphene/WSe 2 /SiO 2 samples we observe mobilities of ∼12 000 cm 2 V −1 s −1 . Magnetic-field-dependent resistance measurements on these samples show a peak in the conductivity at low magnetic fields. This dip is attributed to the weak antilocalization (WAL) effect, stemming from spin-orbit coupling. Samples where graphene is encapsulated between WSe 2 (WS 2 ) and hexagonal boron nitride show a much higher mobility of up to ∼120 000 cm 2 V −1 s −1 . However, in these samples no WAL peak can be observed. We attribute this to a transition from the diffusive to the quasiballistic regime. At low magnetic fields a resistance peak appears, which we ascribe to a size effect due to boundary scattering. Shubnikov-de Haas oscillations in fully encapsulated samples show all integer filling factors due to complete lifting of the spin and valley degeneracies.

Microscopic theory of spin relaxation anisotropy in graphene with proximity-induced spin-orbit coupling

“…Central to the derivation of the quantum kinetic equation for the reduced spin den-sity matrix [Eq. (13)] is the assumption of Gaussian disorder. The latter is equivalent to the first Born approximation [53] and thus it neglects any effects from skew scattering (allowed in the C 3v model [28]) and modifications to the energy dependence of the collision integral due to scattering resonances.…”

“…Next, we use the quantum kinetic equation Eq. (13) to obtain the spin Bloch equations governing the spin dynamics. Firstly, we separate the collision integral I[S κ k ] into intra and inter-valley parts, κ = {κ,κ} = {κ, −κ}, with the corresponding matrix elements of the scattering potential…”

Induced spin-orbit coupling in twisted graphene–transition metal dichalcogenide heterobilayers: Twistronics meets spintronics

“…These heterostructures can posses functionalities that the individual constituent layers may not have. In order to increase the SOC in graphene, one of the most actively pursued directions is to interface it with materials that have strong intrinsic SOC, such as transition metal dichalcogenides (TMDCs) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . TMDCs are expected to be good candidates for graphene spintronics for two reasons: i) it was shown that TMDC substrates do not degrade the mobility of graphene 23,26 , and ii) they host a strong intrinsic SOC of the order of 100 meV (10 meV) in their valence (conduction) band 27 and hence can potentially be suitable materials for proximity induced SOC.…”

Probing magnetism via spin dynamics in graphene/2D-ferromagnet heterostructures

“…With respect to graphene/TMDC heterostructures, this approach has proven to be highly successful: measurements of weak antilocalization (WAL) indicate enhanced SOC in the graphene layer [6][7][8][9][10][11][12]; spin switches have been realized based on spin absorption in the TMDC layer [13,14]; predictions of giant spin relaxation anisotropy [15], which may be useful for orientation-dependent spin filtering, have been subsequently confirmed by experiments [16,17]; and recent measurements have indicated sizable charge-tospin conversion in the graphene layer [18,19]. Giant spin lifetime anisotropy has also been predicted in graphene/TI heterostructures [20], and recent measurements of spin transport and WAL have suggested that TIs also induce strong SOC in graphene [21,22].…”