Physics

Direct generation of spin current using ultrashort laser pulses

Experimental schematic and static characteristics. Source: Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.133.106902

An international team of physicists has discovered that they can directly generate spin current using a specific type of ultrashort laser pulse. In a study published in the journal Physical Review Letters, the team generated the spin current using linearly polarized laser pulses and a circularly polarized probe laser.

Spin current is a type of electrical flow that consists of aligned spins of electrons. Theoretically, it has been suggested that spin current could increase the speed of electronic devices. It is also expected that spin current could increase efficiency and reduce energy costs.

Until now, attempts to generate such a current in a practical way have typically involved using a laser to generate spin, albeit indirectly. However, these attempts proved inefficient because the applied laser generated electrons of mixed orientation, which required filtering one or the other. In this new attempt, the research team found a way to generate a spin current directly with electrons of the same orientation.

The researchers created a target block made of 20 alternating layers of platinum and cobalt, each just 1 nanometer thick. They then placed the block in a container and applied a magnetic field from bottom to top, so that the field was perpendicular to the layers in the block. The field was also strong enough to align the spins of electrons in both layered materials.

Next, the researchers shone a polarized laser on the block using a short pulse. They then shone another laser on the same spot, this time with a circularly polarized probe. This shifted the electron spins between the layers that make up the block within a few femtoseconds, which the team notes is faster than other techniques.

When the team tested their setup, they found that the laser suddenly altered the magnetic order within both layers of the block, changing how magnetic it became, and they used theoretical calculations to approximate the interactions of the electrons, which they found to be in agreement with the experimental results.

Further information: Romain Géneaux et al., “Spin dynamics between metallic layers on a few femtosecond time scale,” Physical Review Letters (2024). DOI: 10.1103/PhysRevLett.133.106902

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Citation: Direct Generation of Spin Currents Using Ultrashort Laser Pulses (September 13, 2024) Retrieved September 17, 2024 from https://phys.org/news/2024-09-generating-currents-ultrashort-laser-pulses.html

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