Citation: Doucot, Benoit, Dmitry Kovrizhin, and Roderich Moessner. "Meandering conduction channels and the tunable nature of quantized charge transport." Proceedings of the National Academy of Sciences 121.39 (2024): e2410703121.
Web: https://arxiv.org/abs/2406.08548
Tags: Physical, Hardware, Quantum-hall-effect
This paper shows that in Chern insulators there is NOT always a well-defined edge current. Often, the edge current bleeds into the bulk, giving a thick virtual edge away from the true edge of the sample, along which the current flows. This thick edge still has an incompressible region on its interior, which prevents backscattering between modes going in opposite directions. Thus, the quantization of the Hall current is still quantized.
This theoretical work is motivated by earlier experiments which found that the current was not localized around the edges:
> Rosen, Ilan T., et al. "Measured potential profile in a quantum anomalous Hall system suggests bulk-dominated current flow." Physical review letters 129.24 (2022): 246602.
There are still samples, however, where current IS quantized around the edges. The takeaway from this work is that the details of the current flow in different topological materials which are in the same phase will have drastically different microscopic current flows. The only things which will necessarily be the same between these samples are their universal topological features - namely, the overall current.
The authors call this phenomenon topological censorship. The topological nature of these materials means that their details are protected from the environment, and thus also protected from the experimenter! This makes it very hard to find out what is going on microscopically in these materials. Experimental techniques have finally gotten to the point that they can be used to diagnose these local behaviors, and thus in the coming years we are going to learn a lot of very interesting (non-universal!) physics from looking locally at topological materials.