The fractional quantum Hall (FQH) effect is an exotic quantum phenomenon that occurs when a two-dimensional electron system is subjected to a strong magnetic field at very low temperatures. In this effect, the electrons start behaving as if they have a fraction of the charge of an electron, giving rise to remarkable physics. While edges have traditionally been considered crucial for realizing the FQH effect, due to their role in confining the electrons, recent theoretical proposals have suggested the possibility of realizing the FQH effect even in edge-free systems. One such theoretical possibility is the formation of FQH droplets in the bulk without any edges, leading to a phase known as the "floating FQH phase".

Here, the team, led by Professor Kenji Watanabe, Professor Takashi Taniguchi, and Associate Professor Makoto Koshino, conducted low-temperature transport experiments on a new class of two-dimensional materials, known as twisted bilayer graphene. By studying the electronic properties of these materials under high magnetic fields, the team made an important breakthrough. They discovered a remarkable insulating phase, which exhibits an unexpected quantized Hall conductivity, characteristic of the FQH effect, but without the presence of any discernible edges.

The team also ruled out alternative explanations for the observed quantized Hall conductivity, including those involving topological insulators. Their results strongly support the theoretical predictions of the floating FQH phase, confirming that indeed edges are not necessary for realizing the FQH effect.

Beyond its fundamental significance, the discovery has potential implications for the development of novel electronic devices. Edge-free FQH phases offer a new platform for exploring exotic fractional quantum excitations, and can potentially lead to the development of new types of electronic devices, such as field-effect transistors and quantum Hall bar structures, without relying on edges.

The research provides compelling evidence for the edge-free FQH effect, opening up new avenues for exploring fundamental quantum phenomena and advancing our understanding of condensed matter physics.

The study was published in the prestigious journal Nature.