Breakthrough! Chinese scientists have discovered new magneton states, which could be used in chips and radar

On March 10, the official website of ShanghaiTech University announced that Professor Lu Wei's research group from the School of Physical Science and Technology of ShanghaiTech University has recently made important progress in the direction of photon-magneton interaction and strong coupling regulation. For the first time, the research team discovered a completely new magnetic resonance in a ferromagnetic insulator single crystal, named

Light-induced magneton states

（pump-induced magnon mode, PIM）。 This discovery opens up a whole new dimension for the study of magnetoelectronic and quantum magnetism.

The results were published in Physical Review Letters, a flagship journal in the field of physics.

The title of the paper is "Unveiling a Pump-Induced Magnon Mode via Its Strong Interaction with Walker Modes."

The above news said that the discovery of Professor Lu Wei's team broke through the "monopoly" of the field

Up to more than 60 years

The category of "Walker modes" was discovered

New magneton states

, or can be used in radar, communication, information wireless transmission and other fields.

New magneton states

In 1956, L. Walker, a staff member at Bell Telephone Laboratory in New Jersey, USA. R. Walker) wrote a paper giving a mathematical description of the space-constrained magneton states of magnetic blocks, which were later published, and this magneton state was called Walker modes. Over the next 60 years, almost all of the magnetostates studied in bulk magnetic materials fell into the category of Walker modes.

Professor Yan Peng, School of Physics, University of Electronic Science and Technology of China, State Key Laboratory of Electronic Thin Films and Integrated Devices, and others published a review article "Topological State of Matter and Quantum Effects in Magnetonics" published in the Chinese academic journal "Acta Physics" in 2023, according to the quantized spin wave called magneton (magnon).

Spin wave (spin wave) is the collective excited state of spin precession in magnetic systems, first proposed by physicist Bloch (1952 Nobel laureate in physics) in 1930, to explain the important law of the spontaneous magnetization intensity of ferromagnets with temperature, and then confirmed by physicist Brockhouse (1994 Nobel Prize winner in physics) using inelastic neutron scattering experiments in 1957.

The wavelength of spin wave can be as small as a few nanometers, which can improve the storage density of information, which is conducive to the miniaturization and high integration of magneton devices. Moreover, the transmission of spin waves does not involve the movement of electrons, and can propagate both in magnetic metals and in magnetic insulators, avoiding power dissipation due to Joule heat.

Each magneton carries a spin angular momentum that reduces Planck's constant, so magnetons can also carry and transmit spin information like electrons. The main purpose of magnetics is to replace information carriers with spin waves, and use spin waves to carry out information transmission and logical calculations. Previous information carriers were the charge or spin properties of electrons.

ShanghaiTech University said that magnetoon state is the core concept in electron spin applications, which is the collective excitation of spin in magnetic materials. The origin of macroscopic magnetism is mainly unpaired electrons in the material. Electrons have two well-known fundamental properties: charge and spin. The former is the object of manipulation by all electronic devices. Spin, especially in magnetic insulators, can completely avoid the ohmic loss of conductive electrons, and give full play to the advantages of long life and low dissipation of spin, so it is of great significance for the development of spintronic devices. Magnetons can also interact with superconducting qubits, playing an important role in quantum information technology.

The newly published study found that under a low magnetic field, when the ferromagnetic insulator single crystal ball is excited by strong microwaves, the internal unsaturated spin will gain a certain degree of synergy, producing a spin wave that oscillates at the same frequency as the microwave excitation signal, which can be named "pump-induced magnon mode (PIM)".

The light-induced magneton state is like a "dark" state, which cannot be directly observed by traditional detection methods, but can be indirectly observed through the cleavage of energy levels generated by its strong coupling with Walker modes, and can be stimulated by microwaves.

Schematic diagram of the spin of an electron: upper spin (left) and lower spin (right). Quantum Mechanics from Migratory Birds: Spin, Entangled States and Geomagnetic Navigation.

The introduction of "electron spin" on the official website of the Institute of High Energy Physics of the Chinese Academy of Sciences said that the concept of spin was introduced for the needs of quantum field theory. Not only electrons have spin, but all microscopic particles such as neutrons, protons, and photons have spin, but the values are different. Spin, like physical quantities such as static mass and charge, is also a physical quantity that describes the inherent properties of microscopic particles. A particle with a spin of 0 is like a dot: it looks the same from any direction. A particle with a spin of 1 is like an arrow: it looks different from different directions.

Spin is different from rotation. According to the article "Quantum Mechanics of Migratory Birds: Spin, Entangled State and Geomagnetic Navigation" released by the WeChat public account of the Institute of High Energy Physics of the Chinese Academy of Sciences, we cannot understand spin from a classical perspective. Current theories and experiments have not found a lower radius of electrons, so electrons are treated as point particles. According to the Pauli exclusion principle, two electrons cannot be in the same state, so the electrons around the nucleus are generally distributed in pairs, and two electrons can be accommodated in an atomic orbital, one spin up and one spin down. The spin orientation of these two electrons cannot be the same, and they are in a state of association, which is what we usually call a quantum entangled state.

Excited states are used to describe the state in which electrons are excited to a higher energy level after atoms, molecules, etc. absorb energy. After that, the electron may make a transition to a lower energy level for a short period of time, releasing a certain amount of energy, such as releasing photons, or returning to the ground state.

There is no electronic noise, which can be used for radar accurate detection

ShanghaiTech University said above,

chip

The research and development mainly follows Moore's Law, which doubles the performance of chips every 18 months to two years. However, as human society gradually enters the post-Moore era, blindly reducing the chip manufacturing process has been "challenged to the limit". The time to double the performance of the processor has been extended, and the momentum of "crazy" has encountered a technical bottleneck. Driven by market demand, people urgently need the injection of "new blood" to activate

Low power consumption, high integration, high information density information processing carrier

of the way out.

The rapid development of spintronics and magnetoelectronic based on the development of magnetic materials provides a way out for breaking through the above limitations.

The research team also found that the newly published light-induced magneton states are rich in nonlinearity that produces a magneton frequency comb.

Frequency comb (top). Schematic diagram of the spin wave frequency combing produced by nonlinear magnon-skyrmion scattering. From Magnonic Frequency Comb through Nonlinear Magnon-Skyrmion Scattering.

This new frequency comb is a new type of frequency comb compared to the frequency comb generated in a microwave resonant circuit

There is no electronic noise

Therefore, it is expected to realize ultra-low noise signal conversion in information technology.

"Conventional magneton strongly coupled states rely on resonators to construct... We get rid of this dependence and can generate a strongly coupled state of magnetons through external microwave induction. Coupling state under such an open boundary

It is expected to be organized like Lego

for rich functionality. Team leader Professor Lu Wei said.

Lu Wei said, "The frequency comb we found is in the microwave frequency band, which is the frequency band used by radar, communication, and information wireless transmission, and it can be predicted that our frequency comb will inevitably play a role in these fields." ”

Lu Wei explained that the frequency comb is like a vernier caliper, which can accurately measure the wind and grass on the spectrum. The optical frequency comb (optical frequency comb) discovered before has shown amazing accuracy in atomic clocks and ultra-sensitive detection.

The research work was jointly completed by ShanghaiTech University, Shanghai Institute of Technical Physics, Chinese Academy of Sciences and Huazhong University of Science and Technology, with ShanghaiTech University as the first completion unit. The first author of the paper is Rao Jinwei, assistant researcher of the School of Physics, Shanghai University of Science and Technology, and the corresponding authors are Professor Lu Wei of the School of Physics of Shanghai University of Science and Technology, Yao Bixi, associate researcher of Shanghai Institute of Technology, Chinese Academy of Sciences, and Professor Yu Tao of Huazhong University of Science and Technology.

Paper Link:

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.046705