In typical metals, electrons can move freely in any direction until they encounter an obstacle, where they experience resistance and scatter randomly. However, in certain exotic materials, electrons may become locked to the material’s edge and flow in a single direction without friction, much like ants marching along a blanket’s boundary. This rare “edge state” allows electrons to glide effortlessly around obstacles while sticking to the material’s perimeter-focused flow, unlike in a superconductor where all electrons flow without resistance.
Physicists at MIT have successfully observed edge states in a cloud of ultracold atoms, capturing images of atoms flowing along a boundary without resistance even when obstacles are present. These findings, published in Nature Physics, could lead to the development of materials that enable super-efficient and lossless transmission of energy and data. By introducing small pieces of this material in future devices, electrons could shuttle along the edges and between different parts of a circuit without any loss, opening up new possibilities for energy transmission.
The study’s co-authors at MIT, including graduate students and faculty, are members of MIT’s Research Laboratory of Electronics and the MIT-Harvard Center for Ultracold Atoms. With direct observations of edge states, physicists hope to manipulate electrons to flow without friction in materials, which could revolutionize the field of energy transmission. The ability to witness this incredible physics firsthand that is usually hidden inside materials provides a new perspective and insight into the behavior of charged particles in certain materials.
The Quantum Hall effect, first observed in 1980, describes an unusual phenomenon where electrons in certain materials are confined to two dimensions under a magnetic field. Physicists proposed the concept of edge states to explain this effect, suggesting that electrons in an applied current could be deflected to the edges of a material and accumulate there. While the occurrence of edge modes is over femtoseconds and across fractions of nanometers, capturing them is incredibly challenging due to their fleeting nature and small scale.
Rather than capturing electrons in edge states, MIT physicists have recreated this physics in a more observable system using ultracold atoms in a carefully designed setup that mimics the behavior of electrons under a magnetic field. By studying the behavior of a cloud of sodium atoms in a laser-controlled trap cooled to nanokelvin temperatures, the researchers witnessed the atoms flowing along the edge without resistance, defying obstacles and obstacles much like electrons would in edge states. This research provides a reliable stand-in for studying how electrons would behave in similar edge states.
The researchers introduced an “edge” in the form of a circular wall created by laser light around the spinning atoms, observing that the atoms flowed along the edge in a single direction without friction. The prolonged, frictionless flow of atoms around the edge persisted even when the researchers placed obstacles in the atoms’ path, demonstrating the resilience and coherence of this edge state. By studying atoms in this system, researchers have validated the behavior predicted to occur in electrons in edge states, establishing a foundation for further exploration and experimentation in the field of quantum physics.
