Spin transistors run faster than traditional transistors and generate less unnecessary heat. Polish physicists added a brick to make this transistor. They proposed a new spin wave propagation control mechanism.
Transistors are commonly used in everyday devices-for example, they can be found in integrated circuits or processors. They can control the flow of electric charge. However, among other things, it is difficult to miniaturize a circuit based on this principle due to the heat generated. Scientists see opportunities for further development in the miniaturization of spintronics. Spintronics does not specifically consider charge, but another quantum feature, that is, the spin of an electron and therefore its internal angular momentum.
Traditional transistors operate using electron transfer. In a spin transistor, the signal will be transmitted through the propagation of spin waves, that is, collective magnetic excitation. Compared with the current transfer mechanism in traditional transistors, this solution has significant advantages. Spin transistors can run faster and generate less heat. However, the possible success of transistors based on the propagation of spin waves depends on the development of effective methods to control the propagation of these waves, which will also be energy-efficient.
Current methods of controlling spin waves by controlling external magnetic fields are too energy-consuming, which prevents them from being applied on a large scale.
Professors Grzegorz Karczewski and Tomasz Wojtowicz of the Institute of Physics of the Polish Academy of Sciences, together with international collaborators, proposed a new mechanism for controlling the propagation of spin waves. The mechanism includes the interference of photons (light) in the spin-orbit interaction. Coupled with the spin and orbital states of conduction electrons that determine its magnetic properties.
The results of the research team were recently published in the well-known scientific journal “Physics Review Letters”. Representatives of the PAS Institute of Physics introduced the research in a press release sent to PAP.
The calculations and experimental results (Raman scattering measurement) included in this work show that the group velocity of spin waves, that is, the propagation velocity of magnetic excitation, depends on the strength of the spin-orbit interaction in the magnetized two-dimensional electron gas.
The experiment carried out used the semiconductor structure-CdMnTe quantum well built by the Institute of Physics of the Polish Academy of Sciences. So-called “optical gating” is used to change the strength of the spin-orbit interaction. Spin transistors form a two-dimensional semiconductor structure. Optical gating consists in appropriately illuminating the structure with light pulses of appropriately selected wavelengths.
This kind of light control changes the concentration of carriers in the two-dimensional conduction channel, changes the spin-orbit interaction, and consequently changes the group velocity of the spin wave.
This mechanism opens the way for new applications of spin waves in devices. The operation of the device will be based on the controlled propagation of these waves (such as the aforementioned transistors), and a lens that focuses the spin waves can also be constructed.
PAP-Science of Poland
lt / March/