New model explains topological phenomenon, Quantum Hall effect in 3D quantum materials

Credit: Physicsworld

The Quantum hall effect, a phenomenon thus far only seen in two-dimensional metals, occurs at low temperatures and strong magnetic fields. But Dr. Tobias Meng and Dr. Johannes Gooth, at ct.mat (Complexity and Topology in Quantum Matter) discovered a 3D phenomenon, like the Quantum Hall effect in a semimetal, ZrTe₅. And this effect could lead to extremely powerful quantum technologies. 

This study is published in the journal, Nature communications.

According to their research, the electrons in zirconium pentatelluride (ZrTe₅) appear to move only in two-dimensional planes despite the material being three-dimensional.

They explain that this Hall effect observed in a three-dimensional material, as electrons move through the material in a three-dimensional plane, but their electron transport appears two-dimensional which could be due to a fraction of electrons were waiting to be activated by an external magnetic field. 

"The way electrons move is consistent in all of our measurements, and similar to what is otherwise known from the two-dimensional quantum Hall effects.  But our electrons move upwards in spirals, rather than being confined to a circular motion in planes. This is an exciting difference to the quantum Hall effect and to the proposed scenarios for what happens in the material ZrTe₅", comments Meng on the genesis of their new scientific model."This only works because not all electrons move at all times. Some remain still as if they were queuing up. Only when an external magnetic field is applied do they become active."

This model was confirmed by further experiments, by cooling the material and applying an external magnetic field, and conducting different measurements, by sending currents through the material, using X-rays, Raman, and electronic spectroscopy. And their result confirmed that the electrons were not moving in a two-dimensional plane. 

Reference: DOI: 10.1038/s41467-021-23435-y