Kinetic Magnetism: Quantum Motion of Atom Gives Rise to New Mechanism for Attraction and Repulsion

Not all magnets exhibit the same properties. People usually think of magnets as a material that sticks to a refrigerator door. Such types of magnets exhibit electronic interactions, which give rise to magnetism. Humans have understood this property for almost a century since the early days of quantum mechanics.

However, many other forms of magnetism exist in nature, and experts are currently discovering the mechanisms that drive these magnets.

New Form of Quantum Magnetism

At Princeton University, physicists have made a significant breakthrough in understanding kinetic magnetism. This achievement was possible using ultracold atoms bound in an artificial laser-built lattice. The details of their research are discussed in the paper "Directly imaging spin polarons in a kinetically frustrated Hubbard system."

The study enabled the scientists to directly image an unusual type of polaron, a quasiparticle that emerges in an interacting quantum system. This microscopic object is the one responsible for this novel type of magnetism. Since it has properties like a spin, a charge, and an effective mass, it acts like a regular particle but not an actual particle like an atom.

The research team, led by physics professor Waseem Bakr, studied the new form of magnetism using ultracold atomic systems. For the first time, they were able to visualize the finely-grained mechanism that gives rise to kinetic magnetism.

The groundwork for the current experiment was laid by a theoretically proposed mechanism for magnetism called Nagaoka ferromagnetism, named after Yosuke Nagaoka. Ferromagnets refer to materials where the spin states of the electrons all point in the same direction.

The research team used vapors of lithium-6 atoms in experiments. This isotope is known for containing three electrons, three protons, and three neutrons. The odd total number makes this atom a fermionic isotope, which means that it behaves similarly to electrons in a solid-state system. When these gases cool down, their behavior starts to be controlled by the principles of quantum mechanisms instead of the more familiar classical ones.

The research team is devising new and innovative approaches to probing this novel, exotic form of magnetism. In the first experiment, the scientists simply took snapshots of the polaron. Now, they are interested in conducting spectroscopic measurements of the polarons.

Potential of Kinetic Magnetism

The origins of kinetic magnetism involve the movement of impurities in the atomic arrangement. This highly unusual motion leads to a powerful magnetism even at very high temperatures. When the magnetism's tunability is combined with doping, kinetic magnetism can be a very promising platform for device applications.

In actual materials, this novel form of magnetism has been observed in moiré materials, which consist of stacked 2D crystals. This has far-reaching implications in condensed matter physics beyond understanding the physics of magnetism. For instance, the more complex version of polarons has been assumed to lead to mechanisms to pair up hole dopants, potentially resulting in superconductivity at high temperatures.

Check out more news and information on Magnetism in Science Times.