Antiferromagnetic THz-frequency Josephson-like Oscillator Driven by Spin Current.

Area of Science:

• Solid State Physics
• Spintronics
• Terahertz (THz) Technology

Background:

• Compact and tunable room-temperature sources for coherent terahertz (THz) signals are needed for new applications.
• Existing THz generation methods (superconductor Josephson junctions, free electron lasers, quantum cascades) require cryogenic temperatures or complex setups, hindering miniaturization and widespread use.

Purpose of the Study:

• To theoretically demonstrate a novel room-temperature source of coherent THz signals.
• To explore the potential of a heavy metal/antiferromagnetic dielectric bi-layer for THz generation.

Main Methods:

• Theoretical modeling of a bi-layer system comprising platinum (Pt) and a bi-axial antiferromagnetic (AFM) dielectric (NiO).
• Investigating the excitation of AFM sublattice magnetization precession via spin current from a DC-current-driven Pt layer.
• Analyzing the THz signal detection using the inverse spin-Hall effect in Pt.

Main Results:

• A Pt/NiO bi-layer is theoretically shown to generate coherent THz signals.
• The frequency of AFM oscillations is tunable from 0.1–2.0 THz by varying the driving current in the Pt layer (10^8–10^9 A/cm^2).
• A THz signal amplitude exceeding 1 V/cm is detected via the inverse spin-Hall effect.

Conclusions:

• The Pt/NiO bi-layer serves as a room-temperature THz-frequency oscillator.
• This AFM-based THz oscillator operates analogously to cryogenic Josephson junction oscillators.
• The easy-plane magnetic anisotropy energy in the AFM plays a role comparable to Josephson energy.