Rutgers Physicists Discover Exotic Quantum State at Material Interface

Physicists at Rutgers University have identified an unusual quantum state that does not fit neatly into the conventional categories of solid, liquid, gas or plasma. Published in Science Advances, the study examined the interface between two exotic magnetic materials, Eu₂Ir₂O₇ and Dy₂Ti₂O₇. The first is a Weyl semimetal, while the second is a magnetic insulator known as spin ice. Researchers said the two materials had previously been studied separately but had not been combined in this way.

At extremely low temperatures and under intense magnetic fields, the team observed a distinctive sixfold pattern in the electrical conductivity of the heterostructure. The researchers attributed the behavior to Kondo coupling, in which the changing magnetic state of the spin ice affects how electrons scatter along surface states of the Weyl semimetal. As the magnetic field increased further, the sixfold pattern collapsed into a twofold pattern, indicating rotational symmetry breaking and suggesting the emergence of a many-body quantum state driven by interactions among numerous particles.

The experiment required an atoms-thick heterostructure fabricated using a specialized instrument known as the Quantum Phenomena Discovery Platform, or Q-DiP, developed by Rutgers researchers after years of experimentation. Further measurements were conducted at the National High Magnetic Field Laboratory in Florida, while a theoretical team spent more than two years modelling the results. The researchers said the findings demonstrate that interfaces between different quantum materials can exhibit physical phenomena absent from either material individually, potentially opening new avenues for controlling electronic and magnetic properties.