Ultrafast ghost Hall states in a 2d altermagnet
Ruikai Wu, Deepika Gill, Sangeeta Sharma, Sam Shallcross
TLDR
This paper demonstrates that 2D altermagnets exhibit ultrafast, light-controlled valley states, enabling spin-polarized currents and a unique "ghost Hall" effect.
Key contributions
- Demonstrates 2D altermagnets (Cr2SO) host valley states controllable by femtosecond laser light.
- Shows linearly polarized light excites charge at specific valleys based on polarization direction.
- Achieves nearly 100% spin-polarized valley currents, advancing valleytronics applications.
- Identifies a "ghost Hall" effect, creating orthogonal spin and charge currents ultrafast.
Why it matters
This research establishes 2D altermagnets as a promising platform for ultrafast light-matter interaction. It opens new avenues for controlling spin and charge currents at femtosecond timescales, crucial for developing next-generation spintronic and valleytronic technologies.
Original Abstract
Two-dimensional materials that exhibit optically active spin and valley degrees of freedom represent one of the most fascinating -- and potentially most technologically useful -- platforms for the ultrafast interaction of light and matter. Here we show, via the example of Cr$_2$SO, that two dimensional altermagnets host valley states controllable by femtosecond laser light: linearly polarized light pulses excite charge at one of two inequivalent valleys, with which valley charge is excited at determined by the polarization vector direction. This underpins a rich spin and valley physics including: (i) valleytronics $-$ the generation of nearly 100$\%$ spin polarized valley currents, as well as (ii) a "ghost Hall" effect $-$ the ultrafast creation of states in which spin and charge currents are orthogonal without invoking Hall physics. Our findings establish 2d altermagents as a platform providing a new route for the control of spin- and charge currents at ultrafast times.
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