How hydrogen ions can control electronic properties of quantum material
12 Jan 2025

A team of physicists from the City College of New York (CCNY) has come up with an unprecedented technique to control the electronic properties of a magnetic Weyl semimetal.

The exotic material features electrons that behave like massless particles known as Weyl fermions.

The new method uses hydrogen cations (H+) to tune these properties, possibly leading to next-gen materials and technologies.

Weyl fermions: Unique particles with potential for advanced technologies
Particle properties

Weyl fermions are unique particles first proposed in theoretical physics, but discovered in condensed matter as excitations in Weyl semimetals.

These materials show special band crossings, known as Weyl nodes, when time-reversal or inversion symmetry is broken.

The researchers propose this discovery could pave the way for new quantum devices using unique topological states for advanced technologies, like chiral nano-electronics and error-proof quantum computing.

Hydrogen ions: A tool to fine-tune Weyl nodes
Technique explained

The CCNY team has devised a way to fine-tune topological properties in ferromagnetic Weyl semimetals with hydrogen.

By adding and removing hydrogen in MnSb2Te4, they managed to modify the material's band structure, forming strongly tilted Weyl nodes.

This process showed that electric charges can behave differently, depending on the rotation direction of an in-plane magnetic field, clockwise or counterclockwise.

Hydrogen-altered Weyl nodes enable advanced charge transport
Enhanced properties

The modified Weyl states also exhibit enhanced properties, such as a doubled Curie temperature (the point where magnetism weakens) and a unique "chiral switch."

This switch uses topological Berry curvature, the chiral anomaly, and hydrogen-altered Weyl nodes to allow advanced, controllable charge transport.

"The major advance of this work is enlarging the breadth of designer topological quantum materials beyond nature's blueprint," said Krusin-Elbaum, a professor in CCNY's Division of Science.

Quantum phenomena and potential applications
Future implications

The study aims to reveal new quantum phenomena, such as the Quantum Anomalous Hall (QAH) effect, which enables an insulator to conduct current without energy loss via 2D superconductivity, surface channels, and axion states with quantized thermal transport.

These findings, as researchers say, have the potential to lead to energy-efficient technologies.

The demonstrated technique is extremely versatile and could greatly improve the capabilities of intrinsic topological magnets, leading to the advancement of future quantum electronics.