Unraveling the Spin-to-Charge Current Conversion Mechanism and Charge Transfer Dynamics at Interface of Graphene/WS$_2$ Heterostructures at Room Temperature

TL;DR

This study investigates spin-to-charge conversion and charge transfer at graphene/WS2 interfaces, revealing enhanced efficiency due to interfacial effects, supported by experimental and theoretical analyses, with implications for spintronic device optimization.

Contribution

It provides the first detailed experimental and theoretical analysis of spin-to-charge conversion mechanisms at graphene/WS2 interfaces at room temperature.

Findings

Spin-to-charge conversion is attributed to inverse Rashba-Edelstein effect.

Charge transfer dynamics are more efficient in heterostructures than in individual layers.

DFT calculations reveal Rashba spin-orbit splitting and electronic coupling.

Abstract

We report experimental investigations of spin-to-charge current conversion and charge transfer dynamics (CT) at the interface of graphene/WS$_2$ van der Waals heterostructure. Pure spin current was produced by the spin precession in the microwave-driven ferromagnetic resonance of a permalloy film (Py-Ni$_{81}$Fe$_{19}$) and injected into the graphene/WS$_2$ heterostructure through the spin pumping process. The observed spin-to-charge current conversion in the heterostructure is attributed to inverse Rashba-Edelstein effect (IREE) at the graphene/WS$_2$ interface. Interfacial CT dynamics in this heterostructure was investigated based on the framework of core-hole-clock (CHC) approach. The results obtained from spin pumping and CHC studies show that the spin-to-charge current conversion and charge transfer process are more efficient in the graphene/WS$_2$ heterostructure compared to isolated WS2 and graphene films. The results show that the presence of WS$_2$ flakes improves the current conversion efficiency. These experimental results are corroborated by density functional theory (DFT) calculations, which reveal (i) Rashba spin-orbit splitting of graphene orbitals and (ii) electronic coupling between graphene and WS$_2$ orbitals. This study provides valuable insights for optimizing the design and performance of spintronic devices.