Items tagged with "quantum hall effect"
These days, movies and video games render increasingly realistic 3-D images on 2-D screens, giving viewers the illusion of gazing into another world. For many physicists, though, keeping things flat is far more interesting.
A team of researchers has devised a simple way to tune a hallmark quantum effect in graphene—the material formed from a single layer of carbon atoms—by bathing it in light. Their theoretical work, which was published recently in Physical Review Letters, suggests a way to realize novel quantum behavior that was previously predicted but has so far remained inaccessible in experiments.
When it comes to quantum physics, light and matter are not so different. Under certain circumstances, negatively charged electrons can fall into a coordinated dance that allows them to carry a current through a material laced with imperfections. That motion, which can only occur if electrons are confined to a two-dimensional plane, arises due to a phenomenon known as the quantum Hall effect.
From NIST-PML--JQI scientists have achieved a major milestone in simulating the dynamics of condensed-matter systems – such as the behavior of charged particles in semiconductors and other materials – through manipulation of carefully controlled quantum-mechanical models.
JQI researchers led by Mohammad Hafezi report detailed measurements of the transmission (how much energy is lost) and delay for edge-state light and for bulk-route light on a photonic chip.
In this week’s issue of Nature Photonics scientists at the Joint Quantum Institute (*) report the first observation of topological effects for light in two dimensions, analogous to the quantum Hall effect for electrons. To accomplish this, they built a structure to guide infrared light over the surface of a room temperature, silicon-on-insulator chip.
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.