Abstract
Van der Waals heterostructures composed of multiple few layer crystals allow the engineering of novel materials with predefined properties. As an example, coupling graphene weakly to materials with large spin–orbit coupling (SOC) allows to engineer a sizeable SOC in graphene via proximity effects. The strength of the proximity effect depends on the overlap of the atomic orbitals, therefore, changing the interlayer distance via hydrostatic pressure can be utilized to enhance the interlayer coupling between the layers. In this work, we report measurements on a graphene/WSe2 heterostructure exposed to increasing hydrostatic pressure. A clear transition from weak localization to weak antilocalization is visible as the pressure increases, demonstrating the increase of induced SOC in graphene.
Highlights
Graphene-based van der Waals heterostructures became one of the most studied physical systems in material science in recent years, which led to the emergence of designer electronics[1,2]
A prominent example is the moiré effect caused by the rotation of the graphene and the underlying other lattice. This led to the Hofstadter physics and formation of secondary charge neutrality points (CNPs) when graphene is placed on hexagonal boron nitride[3,4,5,6,7,8,9,10], whereas correlated phases including superconductivity correlated insulators or ferromagnetic states have been found if it is placed on another graphene sheet[11,12,13,14]
A wide range of experiments demonstrated the presence of proximity-induced spin–orbit coupling (SOC) in various heterostructures by weak localization (WL), capacitance, or spin transport measurements, and it has been found that Rashba and valley–Zemann-like SOC is induced in graphene leading to a large spin relaxation anisotropy[24,25,26,27,28,29,30,31,32,33,34,35]
Summary
Graphene-based van der Waals (vdW) heterostructures became one of the most studied physical systems in material science in recent years, which led to the emergence of designer electronics[1,2]. A wide range of experiments demonstrated the presence of proximity-induced SOC in various heterostructures by weak localization (WL), capacitance, or spin transport measurements, and it has been found that Rashba and valley–Zemann-like SOC is induced in graphene leading to a large spin relaxation anisotropy[24,25,26,27,28,29,30,31,32,33,34,35] Since this enhancement of SOC originates from the hybridization of graphene’s π orbitals with the TMDC layer’s outer orbitals, the strength of the SOC depends strongly on the overlap of the orbital wavefunctions and, on the interlayer distance, which is determined by the vdW force. The pressure control adds another knob with which the electronic properties of 2D materials can be engineered, allowing to more robust proximity states or even engineer novel states of matter
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