{"id":158,"date":"2023-11-06T16:00:34","date_gmt":"2023-11-06T15:00:34","guid":{"rendered":"https:\/\/physicsworld.com\/?p=111019"},"modified":"2024-01-23T11:22:49","modified_gmt":"2024-01-23T10:22:49","slug":"electrons-caught-going-around-the-bend","status":"publish","type":"post","link":"https:\/\/hadamard.com\/c\/electrons-caught-going-around-the-bend\/","title":{"rendered":"Electrons caught going around the bend"},"content":{"rendered":"<figure id=\"attachment_111020\" class=\"size-full\"><a title=\"Click to open image in popup\" href=\"https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current.jpg\" data-featherlight=\"image\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-111020 size-full\" src=\"https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current.jpg\" sizes=\"auto, (max-width: 750px) 100vw, 750px\" srcset=\"https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current.jpg 750w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-211x166.jpg 211w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-317x249.jpg 317w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-508x400.jpg 508w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-524x412.jpg 524w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-521x410.jpg 521w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-635x500.jpg 635w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-250x197.jpg 250w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-245x193.jpg 245w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-300x236.jpg 300w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-114x90.jpg 114w, https:\/\/physicsworld.com\/wp-content\/uploads\/2023\/11\/Streamlines-of-electronic-current-128x101.jpg 128w\" alt=\"Graphs showing the smooth flow of photocurrent streamlines around a microscopic structure shaped like an airplane wing. Several silhouettes of an airplane taking off are shown for comparison\" width=\"750\" height=\"590\" \/><\/a><script type=\"application\/json\">\"Follow the flow: Graphs showing the smooth flow of photocurrent streamlines around a microscopic structure shaped like an airplane wing. This electrofoil (top left) makes it possible to contort, compress and expand photocurrent streamlines in the same way that aeroplane wings (shown in silhouettes at right) contort, compress and expand the flow of air. The researchers examined the fluid-like properties of electronic current (an incompressible, irrotational fluid) through nanoscale devices. (Courtesy: UCR\\\/QMO Lab)\"<\/script><figcaption class=\"gallery-item__caption\">Follow the flow: Graphs showing the smooth flow of photocurrent streamlines around a microscopic structure shaped like an aeroplane wing. This electrofoil (top left) makes it possible to contort, compress and expand photocurrent streamlines in the same way that aeroplane wings (shown in silhouettes at right) contort, compress and expand the flow of air. (Courtesy: UCR\/QMO Lab)<\/figcaption><\/figure>\n<p>&nbsp;<\/p>\n<p>Taking inspiration from the flow of air around aeroplane wings, researchers in the US have imaged photoexcited electrons flowing around sharp bends for the first time. Because such bends are often found in integrated optoelectronic circuits, observing the electrons\u2019 \u201cstreamlines\u201d could lead to improvements in circuit design.<\/p>\n<p>&nbsp;<\/p>\n<p>More than 80 years ago, the physicists William Shockley and Simon Ramo showed theoretically that when electrons travel around bends, their streamlines get locally compressed, producing heat. Until now, though, no-one had measured this effect directly because it is so difficult to observe the streamlines of electron photocurrents \u2013 that is, electric currents induced by light \u2013 through a working device.<\/p>\n<p>&nbsp;<\/p>\n<p>In the new work, which is described in the <a href=\"https:\/\/www.pnas.org\/doi\/10.1073\/pnas.2221815120\" target=\"_blank\" rel=\"noopener noreferrer\"><em>Proceedings of the National Academy of Sciences<\/em><\/a>, researchers led by physicists <a href=\"https:\/\/profiles.ucr.edu\/app\/home\/profile\/gabor\" target=\"_blank\" rel=\"noopener noreferrer\">Nathaniel Gabor<\/a> and <a href=\"https:\/\/www.davemayesphysics.com\/\" target=\"_blank\" rel=\"noopener noreferrer\">David Mayes<\/a> of the <a href=\"https:\/\/qmolab.ucr.edu\/members\/\" target=\"_blank\" rel=\"noopener noreferrer\">University of California, Riverside<\/a> built a micromagnetic heterostructure device made from a layer of platinum on a yttrium iron garnet (YIG) substrate and placed it in a rotating magnetic field. They then directed a laser beam onto the YIG, causing the device to heat up and triggering a phenomenon known as the photo-Nernst effect. It is this effect that generates the photocurrent.<\/p>\n<p>&nbsp;<\/p>\n<h3>Observing the overall pattern of streamlines<\/h3>\n<p>&nbsp;<\/p>\n<p>By changing the direction of the external magnetic field, the team \u201cinject the current in such a way that we not only control its source location, but also its direction,\u201d explains Mayes. What is more, he adds, \u201cit turns out that when you measure the electronic response as you do this over and over, you end up observing the overall pattern of streamlines.\u201d<\/p>\n<p>&nbsp;<\/p>\n<p>To demonstrate the power of their technique, the researchers repeated the experiments on a modified device called an electrofoil that enabled them to contort, compress and expand the photocurrent streamlines in the same way that aeroplane wings contort, compress, and expand the flow of air. In both scenarios, the streamlines represent the direction of flow that yields the greatest response at each point, as predicted by Shockley and Ramo\u2019s theorem.<\/p>\n<p>&nbsp;<\/p>\n<p>\u201cBack in the late 1930s, these two eminent physicists realized that a free charge in a device does not have to reach an electrode to induce an electric response,\u201d Mayes tells <em>Physics World<\/em>. \u201cInstead, the motion of the free charges will affect all the other charges in the device due to the Coulomb force.<\/p>\n<p>&nbsp;<\/p>\n<p>\u201cShockley and Ramo were able to show that the streamlines not only illustrate the \u2018preferred\u2019 current direction for the device, but that they also represent the pattern of current flow through it as if we had simply biased one end of the device and grounded the other.\u201d<\/p>\n<p>&nbsp;<\/p>\n<h3>Avoiding hot spots<\/h3>\n<p>&nbsp;<\/p>\n<p>Gabor notes that being able to determine where current flow lines are being compressed in a device could help circuit designers avoid creating such local hot spots. \u201cThe results from our study also suggest that you should not have sharp bend features in your electrical circuit,\u201d he says, adding that gradually curving wires are \u201cnot the state-of-the-art right now\u201d.<\/p>\n<p>The researchers are now exploring ways of increasing the resolution of their technique while also testing new devices and materials. In particular, they would like to measure streamlines in devices fashioned into geometries such as a \u201cTesla valve\u201d, which constrains electron flow in one direction.<\/p>\n<p>\u201cOur measurement tool is a powerful way to visualize and characterize charge flow optoelectronic devices,\u201d says Gabor. \u201cWe hope to advance our ideas towards new emerging materials that include both magnetic Nernst-like effects and unconventional current flow behaviour.\u201d<\/p>\n<p>The post <a href=\"https:\/\/physicsworld.com\/a\/electrons-caught-going-around-the-bend\/\" rel=\"nofollow\">Electrons caught going around the bend<\/a> appeared first on <a href=\"https:\/\/physicsworld.com\" rel=\"nofollow\">Physics World<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Follow the flow: Graphs showing the smooth flow of photocurrent streamlines around a microscopic structure shaped like an aeroplane wing. This electrofoil (top left) makes it possible to contort, compress and expand photocurrent streamlines in the same way that aeroplane wings (shown in silhouettes at right) contort, compress and expand the flow of air. (Courtesy:&hellip; <a class=\"more-link\" href=\"https:\/\/hadamard.com\/c\/electrons-caught-going-around-the-bend\/\">Continue reading <span class=\"screen-reader-text\">Electrons caught going around the bend<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-158","post","type-post","status-publish","format-standard","hentry","category-allgemein","entry"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/posts\/158","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/comments?post=158"}],"version-history":[{"count":1,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/posts\/158\/revisions"}],"predecessor-version":[{"id":551,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/posts\/158\/revisions\/551"}],"wp:attachment":[{"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/media?parent=158"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/categories?post=158"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/hadamard.com\/c\/wp-json\/wp\/v2\/tags?post=158"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}