Physicists transfer electron spin to photons| Trending Viral hub

A team of physicists led by Dr Yuan Lu from the Jean Lamour Institute at the University of Lorraine has used electrical pulses to manipulate magnetic information and convert it into a polarized light signal, a discovery that could revolutionize long-distance optical telecommunications, including between Earth and Mars. The advance affects the field of spintronics, whose objective is to manipulate the spin of electrons to store and process information.

Structure of SOT spin-LED: controlling the intensity of emitted light and charging current is the basis for information transfer and processing;  In contrast, robust information storage and magnetic random access memories are implemented using carrier spin and associated magnetization in ferromagnets;  The missing link between the respective disciplines of photonics, electronics and spintronics is to modulate the circular polarization of the emitted light, rather than its intensity, through electrically controlled magnetization;  Dainone et al.  demonstrated that this missing link is established at room temperature and with zero applied magnetic field in light-emitting diodes through the transfer of angular momentum between photons, electrons, and ferromagnets.  Image credit: Dainone et al., doi: 10.1038/s41586-024-07125-5.

Structure of SOT spin-LED: controlling the intensity of emitted light and charging current is the basis for information transfer and processing; In contrast, robust information storage and magnetic random access memories are implemented using carrier spin and associated magnetization in ferromagnets; The missing link between the respective disciplines of photonics, electronics and spintronics is to modulate the circular polarization of the emitted light, rather than its intensity, through electrically controlled magnetization; dainone et al. demonstrated that this missing link is established at room temperature and with zero applied magnetic field in light-emitting diodes through the transfer of angular momentum between photons, electrons, and ferromagnets. Image credit: Dainone et al., two: 10.1038/s41586-024-07125-5.

In spintronics, which has been used successfully in magnetic computer hard drives, information is represented by the spin of the electron and, by its representative, the direction of magnetization.

Ferromagnets, such as iron or cobalt, have an unequal number of electrons whose spins are oriented along or against the axis of magnetization.

Electrons with spin along the magnetization travel smoothly through a ferromagnet, while those with opposite spin orientation bounce back. This represents binary information, 0 and 1.

The resulting change in resistance is the key principle of spintronic devices, whose magnetic state, which can be considered stored information, is maintained indefinitely.

Just as a refrigerator magnet requires no energy to stay stuck to the door, spintronic devices would require much less energy than conventional electronics.

However, similar to lifting a fish out of water, the spin information is quickly lost and cannot travel very far when the electrons are removed from the ferromagnet.

This important limitation can be overcome by using light through its circular polarization, also known as helicity, as another spin carrier.

Just as centuries ago humans used carrier pigeons to transport written communications farther and faster than could be done on foot, the trick would be to transfer the spin of electrons to photographs, the quantum of light.

The presence of spin-orbit coupling, which is also responsible for the loss of spin information outside the ferromagnet, makes such transfer possible.

The crucial missing link is then to electrically modulate the magnetization and thus change the helicity of the emitted light.

“The concept of rotating LEDs was initially proposed at the end of the last century,” said Dr. Lu.

“However, to transition to a practical application, it must meet three crucial criteria: room temperature operation, no need for a magnetic field, and electrical controllability.”

“After more than 15 years of dedicated work in this field, our collaborative team has successfully overcome all obstacles.”

In their research, Dr. Lu and his colleagues successfully changed the magnetization of a spin injector by an electrical pulse using the spin orbit torque.

The electron spin is rapidly converted into information contained in the helicity of the emitted photons, allowing seamless integration of magnetization dynamics with photonic technologies.

This electrically controlled spin photon conversion is now achieved in light-emitting diode electroluminescence.

In the future, by implementing in semiconductor laser diodes, so-called spin lasers, this highly efficient information encoding could pave the way for fast communication at interplanetary distances, since the polarization of light can be conserved in space propagation. , which could make it the fastest mode of communication between Earth and Mars.

It will also greatly benefit the development of various advanced technologies on Earth, such as optical quantum computing and communication, neuromorphic computing for artificial intelligence, ultra-fast and highly efficient optical transmitters for data centers or Light-Fidelity applications.

“The realization of in-orbit spin and torque injectors is a decisive step that will greatly advance the development of ultrafast and energy-efficient spin lasers for the next generation of quantum and optical communication technologies,” said Professor Nils Gerhardt of the University of the Ruhr.

The teams work was published in the magazine Nature.

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PA Dainone et al. 2024. Control of light helicity by electrical magnetization switching. Nature 627, 783-788; doi:10.1038/s41586-024-07125-5

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