Spectroscopy for Strain-Modulated Terahertz Magnonics

Introduction

Motivated by the recent discovery of a giant strain-induced blue-shift of Terahertz antiferromagnetic spin waves (magnons) in the spin-orbit Mott insulators Sr2IrO4 and Ca2RuO4 by the PI and his group, the SpecTera project will explore whether strain modulation can be harnessed to confine and guide THz magnons.

Instrument Development

To probe magnetic order and magnon excitations in inhomogeneous strain environments with high energy and momentum resolution, we will develop a combination of:

• Raman scattering instruments
• Brillouin scattering instruments
• Resonant x-ray scattering instruments

This includes a new “momentum microscopy” facility that will generate momentum-space images of magnetic order and excitations with micro-focused x-ray beams.

Materials Platform

To establish a materials platform for SpecTera, we will use these instruments for surveys of the strain response of different spin-orbit Mott insulators, including compounds with antiferromagnetic order above room temperature.

The magnetic ground state and excitations of selected model compounds will be mapped out in carefully tailored strain environments in thermal equilibrium. This will be followed by experiments to probe their response to controlled non-equilibrium situations, including:

1. Thermal gradients
2. Local excitation of magnons by intense sub-THz sources

Strain Profile Patterning

Inspired by methods developed in semiconductor physics, we will pattern strain profiles by electron beam lithography and assess their ability to serve as magnon conduits.

Interaction with Dynamic Strain

Finally, we will explore the interaction of magnons in spin-orbit Mott insulators with dynamic strain generated by surface acoustic waves.

Conclusion

SpecTera will create a new nexus between the rapidly evolving research fields of Terahertz magnonics and correlated-electron physics, and harness the resulting synergies to explore pathways towards a novel architecture of magnonic devices.