Giant bipolar unidirectional photomagnetoresistance

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Positive magnetoresistance (PMR) and negative magnetoresistance (NMR) are distinct magnetic field responses.
• Materials exhibiting giant PMR or NMR typically differ due to their underlying physics.

Purpose of the Study:

• To investigate photomagnetoresistance in van der Waals heterojunctions.
• To explore the coexistence and characteristics of giant PMR and NMR in a single device.
• To understand the physical mechanisms behind the observed magneto-optical transport phenomena.

Main Methods:

• Fabrication of WSe2/quasi-two-dimensional electron gas van der Waals heterojunctions.
• Experimental measurements of magnetoresistance under varying magnetic fields and WSe2 layer thicknesses.
• Theoretical investigations involving spin splitting, photocarrier recombination, and the Zeeman effect.

Main Results:

• Observed coexistence of giant PMR (up to 4,900,000%) and giant NMR (up to -99.8%) in a single device.
• Demonstrated giant unidirectional magnetoresistance (UMR) spanning over two orders of magnitude.
• Identified the phenomenon as giant bipolar unidirectional photomagnetoresistance.

Conclusions:

• The observed phenomena stem from strong out-of-plane spin splitting, magnetic field-enhanced photocarrier recombination, and the Zeeman effect.
• This discovery offers a pathway for developing high-performance, light-tunable spintronic devices.