Accessing Ultrafast Spin-Transport Dynamics in Copper Using Broadband Terahertz Spectroscopy

Area of Science:

• Condensed matter physics
• Materials science
• Spintronics

Background:

• Understanding electron spin transport dynamics is crucial for developing next-generation electronic devices.
• Nanometer-thick metallic layers present unique challenges and opportunities for spin transport phenomena.

Purpose of the Study:

• To investigate the spatiotemporal dynamics of ultrafast electron spin transport in copper.
• To determine the transport regime (ballistic vs. diffusive) in nanometer-thick copper films.

Main Methods:

• Utilized ultrabroadband terahertz emission spectroscopy.
• Analyzed temporal delays, broadening, and attenuation of spin-current pulses.

Main Results:

• Observed ballisticlike propagation of the spin-current pulse peak, approaching the Fermi velocity.
• Identified significant velocity dispersion and diffusive features.
• Determined the diffusion-dominated transport regime for distances greater than 2 nm using frequency-dependent Fick's law.

Conclusions:

• Electron spin transport in nanometer-thick copper exhibits both ballistic and diffusive characteristics.
• The findings provide critical insights for designing efficient broadband spintronic devices.