Items tagged with "topological insulator"
Everything radiates. Whether it's a car door, a pair of shoes or the cover of a book, anything hotter than absolute zero (i.e., pretty much everything) is constantly shedding radiation in the form of photons, the quantum particles of light.
A twin process—absorption—is usually also present. As photons carry away energy, passers-by from the environment can be absorbed to replenish it. When absorption and emission occur at the same rate, scientists say that an object is in equilibrium with its environment. This often means that object and environment share the same temperature.
Researchers at the University of Maryland have captured the most direct evidence to date of a quantum quirk that allows particles to tunnel through a barrier like it’s not even there. The result, featured on the cover of the June 20, 2019 issue of the journal Nature, may enable engineers to design more uniform components for future quantum computers, quantum sensors and other devices.
Scientists studying an exotic material have found a potential application for its unusual properties, a discovery that could improve devices found in most digital electronics.
Under the right conditions the material, a compound called samarium hexaboride, is a topological insulator—something that conducts electricity on its surface but not through its interior. The first examples of topological insulators were only recently created in the lab, and their discovery has sparked a great deal of theoretical and experimental interest.
Ring resonators are circular waveguides that are used as optical cavities. They look like tiny racetracks and are often fabricated from silicon. Photons can enter and exit a resonator and even move to neighboring waveguides through evanescent coupling. The micro-rings only let light waves circulate-- “resonate”-- if they have the right wavelength. This image, featured on the cover of the December 2013 issue of Nature Photonics, depicts an array of ring resonators designed to be a photonic analog to electrons experiencing quantum Hall physics. Read more to learn more about these micro-racetracks.
All materials are composed of the same basic stuff--atoms and their electrons. Atoms come in 118 different types, giving rise to enormous variation in material properties. For example, aluminum conducts electricity; add some oxygen and you get insulating aluminum oxide. One is shiny; the latter is whitish and dull.
An old material gets a new name, and with it, topological insulators have another chance to shine. Samarium hexaboride (SmB6) has been around since the late 1960s--but understanding its low temperature behavior has remained a mystery until recently. Experimentalists* have recently confirmed that this material is the first true 3D topological insulator—as originally predicted by JQI/CMTC☨ theorists in 2010.
A group at Delft University in the Netherlands led by L.P. Kouwenhoven has published experimental signatures of Majorana particles. The experiment precisely follows the theoretical proposals made in 2010 by Sankar Das Sarma and his collaborators at JQI.