Controlling the Subpicosecond Coherent Spin and Valley Dynamics with Anomalous Magnetic Proximity Effect

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Information Science

Background:

• Spin-and-valley-tronics utilizes electron spin and valley degrees of freedom for advanced information technology.
• Coherent control of spin and valley dynamics is crucial for quantum operations but faces challenges like subpicosecond valley decoherence.
• The magnetic proximity effect (MPE) is known to modify magnetic and optical properties but its impact on ultrafast dynamics was unexplored.

Purpose of the Study:

• To investigate the influence of MPE on ultrafast coherent spin and valley dynamics in WSe2/CrSBr heterostructures.
• To explore the potential of MPE for enhancing valley Zeeman splitting and emission helicity.
• To understand the mechanisms behind anomalous magneto-optical properties and switchable exchange bias.

Main Methods:

• Fabrication and characterization of WSe2/CrSBr heterostructures.
• Investigation of band structure alignment and charge transfer.
• Ultrafast optical spectroscopy to probe spin and valley dynamics.
• Analysis of magneto-optical properties and exchange bias.

Main Results:

• WSe2/CrSBr heterostructures exhibit strong charge transfer with a noncollinear spin configuration due to resonantly aligned band structures.
• Substantial enhancement in valley Zeeman splitting and emission helicity was observed.
• Subpicosecond coherent spin and valley precession was driven by enhanced exchange coupling and noncollinear charge transfer spin states.
• Anomalous magneto-optical properties and switchable exchange bias were demonstrated.

Conclusions:

• The study reveals that MPE in WSe2/CrSBr heterostructures can drive ultrafast coherent spin and valley dynamics.
• This work demonstrates a pathway for engineering coherent spin and valley precession for quantum applications.
• The findings pave the way for ultrafast encoding and processing of spin and valley information at magnetic van der Waals interfaces.