{"id":6216,"date":"2024-02-27T10:59:03","date_gmt":"2024-02-27T18:59:03","guid":{"rendered":"https:\/\/www.hmc.edu\/physics\/?post_type=physics_colloquium&#038;p=6216"},"modified":"2024-02-23T10:59:34","modified_gmt":"2024-02-23T18:59:34","slug":"electrically-driven-amplification-of-terahertz-acoustic-waves-in-graphene-2","status":"publish","type":"physics_colloquium","link":"https:\/\/www.hmc.edu\/physics\/research\/colloquium\/electrically-driven-amplification-of-terahertz-acoustic-waves-in-graphene-2\/","title":{"rendered":"Electrically driven amplification of terahertz acoustic waves in graphene"},"content":{"rendered":"\n<p>Dr. Aaron Barajas, Postdoctoral Scholar, UC Irvine<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"200\" height=\"200\" src=\"https:\/\/www.hmc.edu\/physics\/wp-content\/uploads\/sites\/22\/2024\/02\/1697171825592-1.jpg\" alt=\"\" class=\"wp-image-6217\" srcset=\"https:\/\/www.hmc.edu\/physics\/wp-content\/uploads\/sites\/22\/2024\/02\/1697171825592-1.jpg 200w, https:\/\/www.hmc.edu\/physics\/wp-content\/uploads\/sites\/22\/2024\/02\/1697171825592-1-150x150.jpg 150w\" sizes=\"auto, (max-width: 200px) 100vw, 200px\" \/><\/figure>\n\n\n\n<p>In graphene devices, the electronic drift velocity can easily exceed the speed of<br>sound in the material at moderate current biases. Under this condition, the<br>electronic system can efficiently amplify acoustic phonons, leading to the<br>exponential growth of sound waves in the direction of the carrier flow. In this<br>talk, I will discuss our findings about how such phonon amplification can<br>significantly modify the electrical properties of graphene devices. We observe a<br>superlinear growth of the resistivity in the direction of the carrier flow when the<br>drift velocity exceeds the speed of sound, resulting in a sevenfold increase over a<br>distance of 8 \u00b5m. The resistivity growth is observed at carrier densities away from<br>the Dirac point and is enhanced at cryogenic temperatures. These observations<br>are explained by a theoretical model for the electrical amplification of acoustic<br>phonons \u2014 reaching frequencies up to 2.2 THz \u2014 where the wavelength is<br>controlled by gate-tunable transitions across the Fermi surface. These findings<br>provide a route to on-chip high-frequency sound generation and detection in the<br>THz frequency range.<\/p>\n","protected":false},"author":335,"featured_media":0,"template":"","class_list":["post-6216","physics_colloquium","type-physics_colloquium","status-publish","hentry"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.hmc.edu\/physics\/wp-json\/wp\/v2\/physics_colloquium\/6216","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.hmc.edu\/physics\/wp-json\/wp\/v2\/physics_colloquium"}],"about":[{"href":"https:\/\/www.hmc.edu\/physics\/wp-json\/wp\/v2\/types\/physics_colloquium"}],"author":[{"embeddable":true,"href":"https:\/\/www.hmc.edu\/physics\/wp-json\/wp\/v2\/users\/335"}],"wp:attachment":[{"href":"https:\/\/www.hmc.edu\/physics\/wp-json\/wp\/v2\/media?parent=6216"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}