Nonlocal Spin Dynamics in the Crossover from Diffusive to Ballistic Transport

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Ultraclean graphene devices enable ballistic transport and advanced spin manipulation.
• Conventional spin diffusion theory is used to analyze spin transport in nonlocal spin valves.
• This theory's applicability is limited in ballistic transport or very long spin diffusion length regimes.

Purpose of the Study:

• To investigate spin transport in graphene nonlocal spin valves under ballistic transport and long spin diffusion length conditions.
• To evaluate the accuracy of conventional spin diffusion theory in these extreme regimes.
• To develop a more comprehensive theoretical framework for spin dynamics in ultraclean 2D materials.

Main Methods:

• Quantum simulations of graphene nonlocal spin valves were performed.
• Simulations covered a wide range of spin dynamics, from diffusive to ballistic transport.
• Results were compared against conventional spin diffusion theory and extended models.

Main Results:

• Conventional spin diffusion theory was found to be inadequate for describing the crossover to ballistic transport.
• The theory also failed to accurately predict spin transport in the limit of long spin diffusion lengths.
• An extension of the current theoretical framework successfully described the long spin diffusion length regime.

Conclusions:

• The study highlights the limitations of existing theories for spin transport in advanced graphene devices.
• An extended theoretical framework is proposed to accurately model spin dynamics across various regimes.
• This work provides new insights for predicting and scrutinizing spin transport in ultraclean 2D material-based devices.