Science Advances: Researchers use light to control nanoscale magnetic fields

It is reported that in a thin two-dimensional semiconductor, electrons move, spin and synchronize in an unusual way. For researchers, understanding the complex movement of these electrons and learning how to manipulate their arrangement can not only solve basic physical problems, but also produce new circuits and equipment.

(A) Single layer structure diagram of WSe2 packaged by hbn, with FLG top grid and contact. (B) D1 Optical microscope image of the sample. (C) Gate related reflection spectrum of WSe2 sample. (D) At 0.5 V σ+ and σ − Reflection spectrum, in which the characteristics of singlet and triplet are well distinguished. (E) σ+ At 0.5 V under pumping σ+ and σ − Reflection spectrum. (F) σ+ and σ − CD spectrum under pumping action.

Such electrons can take a relative phase magnetic order, and they arrange their spins in the same direction. Traditionally, the ability to manipulate the magnetic order in 2D semiconductors has been limited. Scientists use clumsy external magnetic fields, which limit technology integration and may mask interesting phenomena.

The spatial profile of spin polarization.

Researchers at the Pritzker School of Molecular Engineering (PME) at the University of Chicago discovered how to use a nanoscale low-power laser beam to precisely control the magnetism in 2D semiconductors. Their methods, described online in the journal Progress in Science, have an impact on the emergence of research related phases and the design of new optoelectronic and spintronic devices.

"We can now use light to manipulate electrons in this way, which means we have unprecedented control over this magnetic order." Alex High, the senior author of the new work, said.

Controllable magnet

The probe shows that the pulsed laser affects the spin polarization of electrons in the 5 μ m by 8 μ m region of TMD, and diffuses the relevant phase outward from the laser. In other words, electrons are adjusting their spin; Researchers can control the magnetic order of electrons in a small area.

Spin polarization dynamics.

"This new technology provides us with a simple way to operate the electron correlation, making the research of related phases more practical than in the past." Said Kai Hao, a postdoctoral fellow and co first author of the paper.

"This new technology provides us with a simple way to operate the electron correlation, making the research of related phases more practical than in the past." Said Kai Hao, a postdoctoral fellow and co first author of the paper.

Andrew Kindseth, a graduate student, also participated in the new research. He said: "The very attractive thing about this research is that it is quite straightforward. In many ways, it is as simple as irradiating this material with a circularly polarized laser."

New research platform

The dependence of spin polarization on gate, power and temperature.

The researchers said that this new technology to control the magnetism of atomic thin semiconductors provides a starting point for a large number of new research. In addition to the magnetic phase, TMD systems are also assumed to form more exotic related electronic phases, such as Wigner crystals, charge density waves, Mott states, and superconductivity. The ability to locally manipulate the electron spin in tmd with nanoscale accuracy in a very short time scale may provide previously unavailable information, which will further contribute to the theoretical study of these singular phases.

In terms of applications, new optoelectronic and spintronic devices are urgently needed to meet the explosive growth of the information industry. Optical control of spin order has great potential in device applications. Direct effects include spin sources on the chip, tunable optical isolators, and efficient fanouts in spintronic circuits.

Source:Optically controllable magnetism in atomically thin semiconductors, Science Advances (2022). DOI: 10.1126/sciadv.abq7650