Scientists Excite Magnons in Nanostructures With Laser Pulses
Points to note…
+ Physicists from MIPT and the Russian Quantum Center, joined by colleagues from Saratov State University and Michigan Technological University, have demonstrated new methods for controlling spin waves in nanostructured bismuth iron garnet films via short laser pulses. Presented in Nano Letters, the solution has potential for applications in energy-efficient information transfer and spin-based quantum computing.
The researchers relied on 250-femtosecond probe pulses to track the state of the sample and extract spin wave characteristics. A probe pulse can be directed to any point on the sample with a desired delay relative to the pump pulse. This yields information about the magnetization dynamics in a given point, which can be processed to determine the spin wave’s spectral frequency, type, and other parameters.
+ Unlike the previously available methods, the new approach enables controlling the generated wave by varying several parameters of the laser pulse that excites it. In addition to that, the geometry of the nanostructured film allows the excitation center to be localized in a spot about 10 nanometers in size. The nanopattern also makes it possible to generate multiple distinct types of spin waves.
+ The angle of incidence, the wavelength and polarization of the laser pulses enable the resonant excitation of the waveguide modes of the sample, which are determined by the nanostructure characteristics, so the type of spin waves excited can be controlled. It is possible for each of the characteristics associated with optical excitation to be varied independently to produce the desired effect.
+ Unlike the electrical current, spin wave propagation does not involve a transfer of matter. As a result, using magnons rather than electrons to transmit information leads to much smaller thermal losses. Data can be encoded in the phase or amplitude of a spin wave and processed via wave interference or nonlinear effects.
+ A particle’s spin is its intrinsic angular momentum, which always has a direction. In magnetized materials, the spins all point in one direction. A local disruption of this magnetic order is accompanied by the propagation of spin waves, whose quanta are known as magnons.
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