Researchers have made a groundbreaking discovery, predicting the emergence of a new quantum anomalous state of matter in fractionally filled moiré superlattice bands. This intriguing finding could pave the way for a deeper understanding of the complex interplay between topology and charge order in these materials.
Unraveling the Quantum Enigma
With a small twist, 2D moiré superlattices have attracted increasing research interests. Beyond that, these exceptional constructs have been found to be home to a broad and fascinating range of novel physical properties, such as topological quantum fluids, or even electron crystals.
Building upon these recent developments, a group of researchers from California State University Northridge, Stockholm University and the Massachusetts Institute of Technology (MIT) have now investigated how electrons in such moiré materials possess both characteristics. After a flurry of calculations and complex knots are worked out, however, they predict the birth of an electron topological crystal unique to anything seen before.
Then, as if by a cosmic coincidence, A QUANTUM ANOMALY IS REVEALED
This new state of matter recently discovered by the research team bears mixed characteristics, such as intertwined ferromagnetism, charge order and topology. Such a combination is very rare, because topology and local charge order are normally regarded as competing and contradictory phenomena.
States that fall in this class could be found much more typically in moiré superlattices, suggesting crucial experimental signatures ought to embrace a quantized and surprisingly massive zero-field Hall conductance, mentioned research co-author Emil J. Bergholtz. The fact this forms in a scenario where strong Coulomb interactions are prevalent makes it all the more extraordinary. Imagine the system, without these interactions, as just being a metal. However, the topology of the strongly interacting system is still reflected by effectively non-interacting fermions in a Chern insulating state.
Conclusion
Finding these new quantum anomalous crystals in fractionally filled moiré superlattices provides a platform for future work, both for scientific studies and device applications. Crystallization and topology interact in ways that defy our conventional intuition, as witnessed here for the first time, charting a course towards an understanding of moiré materials far richer than merely emergent electromagnetism. The great news for theoreticians is that now follows an exciting period during the exploration of this exotic state as well the discovery of new potential exotic states, by studying more and more different aspects of materials — one thing that has allowed us to advance our knowledge about quantum systems and their possible next applications.
