Injection of a pure spins current into a magnetic insulator modifies the chemical potential of magnons and can lead to intriguing phenomena such as long-range spin transport and magnon condensation. We study nanowires fabricated from a bilayer of a metallic ferromagnet and an insulating ferrimagnet. Via interlayer exchange coupling, magnons can be thermally transferred from one layer into another, constituting a pure spin current. The injection generates a non-equilibrium population of incoherent magnons.
Two-dimensional, or 2D, materials are attracting considerable attention as a testbed for new physics and as candidates for applications in flexible nanoscale high-speed optoelectronics, solar energy conversion, and chemical sensing. Most unique properties of 2D materials stem from their highly anisotropic optical and electronic properties. Terahertz (THz) spectroscopy provides access to those properties with ultra-high time resolution and without the complications of electrical contacts.