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Surprising Control over Photoelectrons from a Topological Insulator

By Guest PostMarch 24, 2013Science3d topological insulators, alessandra lanzara, als, angle resolved, arpes, atoms, berkeley lab, chris jozwiak, data collection, dirac point, dung hai lee, electronic states, energy momentum diagrams, field of spintronics, flight analyzer, german, graphene, incident light, laser beam, magnetic surface, momentum space, p polarized, photoelectrons, photoemission spectroscopy, quantum computing, s polarization, s polarized, senkrecht, spin polarized, spin time, steve louie, strange crystalline materials, tis, topological insulator, university of california, zahid hussain

Berkeley Lab scientists discover how a photon beam can flip the spin polarization of electrons emitted from an exciting new material

Plain-looking but inherently strange crystalline materials called 3D topological insulators (TIs) are all the rage in materials science. Even at room temperature, a single chunk of TI is a good insulator in the bulk, yet behaves like a metal on its surface.

Researchers find TIs exciting partly because the electrons that flow swiftly across their surfaces are “spin polarized”: the electron’s spin is locked to its momentum, perpendicular to the direction of travel. These interesting electronic states promise many uses – some exotic, like observing never-before-seen fundamental particles, but many practical, including building more versatile and efficient high-tech gadgets, or, further into the future, platforms for quantum computing. (more…)

A New Tool to Attack the Mysteries of High-Temperature Superconductivity

By Guest PostJune 8, 2012Scienceabsolute zero, advanced light source, alessandra lanzara, als, band structure, bardeen cooper schrieffer, bcs theory, beams of xrays, Berkeley, berkeley lab, bi2212, christopher smallwood, conventional superconductors, cooper pairs, dung hai lee, electric current, electric grids, electrons, energy savings, femtosecond scale pulses, high tc, high temperature, joseph orenstein, msd, quasiparticles, relaxation process, resistance, superconductivity, synchrotron light sources, through frequency, transmission, ultrafast laser arpes, university of california

Berkeley Lab researchers use an ultrafast laser to better understand high-temperature superconductors

Superconductivity, in which electric current flows without resistance, promises huge energy savings – from low-voltage electric grids with no transmission losses, superefficient motors and generators, and myriad other schemes. But such everyday applications still lie in the future, because conventional superconductivity in metals can’t do the job.

Although they play important roles in science, industry, and medicine, conventional superconductors must be maintained at temperatures a few degrees above absolute zero, which is tricky and expensive. Wider uses will depend on higher-temperature superconductors that can function well above absolute zero. Yet known high-temperature (high-Tc) superconductors are complex materials whose electronic structures, despite decades of work, are still far from clear. (more…)

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Surprising Control over Photoelectrons from a Topological Insulator

A New Tool to Attack the Mysteries of High-Temperature Superconductivity