Nanowerk November 8, 2021 Previously an international team of researchers (Germany, Russia, USA – Arizona State University, Japan) reported that a layer of the semiconductor material molybdenum diselenide generated laser light at cryogenic temperatures. Now they created the same effect at room temperature in exciton-polaritons. If sufficient exciton-polaritons are generated, they merge into a macroscopic quantum state. A sudden increase in light emission from the sample indicates that this transformation has taken place. The resulting radiation has only a single wavelength and displays coherence. To demonstrate the effect, they placed thin layers of tungsten diselenide between special mirrors. By studying the […]
Tag Archives: Valleytronics
Graphene valleytronics: Paving the way to small-sized room-temperature quantum computers
Phys.org September 8, 2021 Electrons in two-dimensional hexagonal materials have an extra degree of freedom that can be used to encode and process quantum information. An international team of researchers (India, Germany) demonstrated that both valley-selective excitation and valley-selective high-harmonic generation can be achieved in pristine graphene by using a combination of two counter-rotating circularly polarized fields, the fundamental and its second harmonic. Controlling the relative phase between the two colors allowed them to select the valleys where the electron–hole pairs and higher-order harmonics are generated. They described an all-optical method for measuring valley polarization in graphene with a weak […]
Scientists develop first electrically-driven ‘topological’ laser
Phys.org February 13, 2020 Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime. An international team of researchers (Singapore, UK) demonstrated an electrically pumped terahertz quantum cascade laser based on topologically protected valley edge states. Unlike topological lasers that rely on large-scale features to impart topological protection, the compact design makes use of the valley degree of freedom in photonic crystals, analogous to two-dimensional gapped valleytronic materials. With regularly spaced emission peaks lasing occurs in a sharp-cornered triangular cavity, even if perturbations are introduced into the […]