Phonon-driven spin-Floquet magneto-valleytronics in MoS₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Spintronics

Background:

• Two-dimensional materials with strong spin-orbit coupling exhibit unique electronic, spintronic, and topological properties.
• Valley degrees of freedom in these materials are of significant interest for encoding binary information.
• Breaking of time or inversion symmetry is crucial for these novel properties.

Purpose of the Study:

• To investigate the coupling between spin, valley momenta, and optical phonons in MoS2.
• To explore the induction of magnetization in non-magnetic two-dimensional materials via phonon pumping.
• To understand the potential for controlling valley states using infrared laser excitation.

Main Methods:

• Ab initio time-dependent density functional theory simulations were performed on MoS2.
• The study focused on the E″ phonon mode that breaks lattice mirror symmetry.
• Floquet spectra of phonon-dressed spins were analyzed to determine magnetic properties.

Main Results:

• Spin in MoS2 is locked to valley momenta and strongly coupled to the optical E″ phonon.
• Pumping the phonon to break time-reversal symmetry induces a net out-of-plane magnetization (≈0.024μB per phonon quantum).
• This magnetic response is observed even in the non-magnetic 2H semiconducting transition-metal dichalcogenides.

Conclusions:

• Phonon-dressed spins in MoS2 can generate magnetization by breaking time-reversal symmetry.
• This phenomenon is general for 2H semiconducting transition-metal dichalcogenides.
• The induced magnetic response can be probed and controlled using infrared coherent laser excitation, offering new avenues for spintronics.