{"id":43254,"date":"2023-03-08T14:50:09","date_gmt":"2023-03-08T15:50:09","guid":{"rendered":"https:\/\/peymantaeidi.net\/stem-cell\/?p=43254"},"modified":"2023-03-08T16:35:59","modified_gmt":"2023-03-08T16:35:59","slug":"circular-route-to-using-graphene-quantum-dots-as-magnetic-field-sensors","status":"publish","type":"post","link":"https:\/\/peymantaeidi.net\/stem-cell\/2023\/03\/08\/circular-route-to-using-graphene-quantum-dots-as-magnetic-field-sensors\/","title":{"rendered":"Circular route to using graphene quantum dots as magnetic field sensors"},"content":{"rendered":"
\"Physicist
Physicist Jairo Velasco Jr (left) and graduate student Zhehao Ge (right) in Velasco\u2019s lab at UCSC. Behind them is the scanning tunneling microscope they use to create and study graphene quantum dots. Photo: Tianhui Zhu.<\/figcaption><\/figure>\n

Trapped electrons traveling in circular loops at extreme speeds inside graphene quantum dots are highly sensitive to external magnetic fields and could be used as novel magnetic field sensors with unique capabilities, according to a new study.<\/p>\n

Electrons in graphene (an atomically thin form of carbon) behave as if they were massless, like photons, which are massless particles of light. Although graphene electrons do not move at the speed of light, they exhibit the same energy-momentum relationship as photons and can be described as \u2018ultra-relativistic\u2019. When these electrons are confined in a quantum dot, they travel at high velocity in circular loops around the edge of the dot.<\/p>\n

\u201cThese current loops create magnetic moments that are very sensitive to external magnetic fields,\u201d explained Jairo Velasco Jr, associate professor of physics at the University of California, Santa Cruz (UCSC). \u201cThe sensitivity of these current loops stems from the fact that graphene electrons are ultra-relativistic and travel at high velocity.\u201d<\/p>\n

Velasco is corresponding author of a paper in Nature Nanotechnology<\/em><\/a> on these new findings. His group at UCSC used a scanning tunneling microscope (STM) to create the quantum dots in graphene and study their properties. His collaborators on the project include scientists at the University of Manchester in the UK and the National Institute for Materials Science in Japan.<\/p>\n

\u201cThis was highly collaborative work,\u201d Velasco said. \u201cWe did the measurements in my lab at UCSC, and then we worked very closely with theoretical physicists at the University of Manchester to understand and interpret our data.\u201d<\/p>\n

The unique optical and electrical properties of quantum dots \u2013 which are often made of semiconductor nanocrystals \u2013 are due to electrons being confined within a nanoscale structure, such that their behavior is governed by quantum mechanics. Because the resulting electronic structure is like that of atoms, quantum dots are often called \u2018artificial atoms\u2019. Velasco\u2019s approach creates quantum dots in different forms of graphene, using an electrostatic \u2018corral\u2019 to confine graphene\u2019s speeding electrons.<\/p>\n

\u201cPart of what makes this interesting is the fundamental physics of this system and the opportunity to study atomic physics in the ultra-relativistic regime,\u201d he said. \u201cAt the same time, there are interesting potential applications for this as a new type of quantum sensor that can detect magnetic fields at the nano scale with high spatial resolution.\u201d<\/p>\n

Additional applications are also possible, according to co-first author Zhehao Ge, a UCSC graduate student in physics. \u201cThe findings in our work also indicate that graphene quantum dots can potentially host a giant persistent current [a perpetual electric current without the need of an external power source] in a small magnetic field,\u201d Ge said. \u201cSuch current can potentially be used for quantum simulation and quantum computation.\u201d<\/p>\n

The study looked at quantum dots in both monolayer graphene and twisted bilayer graphene. The graphene rests on an insulating layer of hexagonal boron nitride, and a voltage applied with the STM tip creates charges in the boron nitride that serve to electrostatically confine electrons in the graphene.<\/p>\n

Although Velasco\u2019s lab uses STM to create and study graphene quantum dots, a simpler system using metal electrodes in a cross-bar array could be used in a magnetic sensor device. Because graphene is highly flexible, the sensor could also be integrated with flexible substrates for magnetic field sensing of curved objects.<\/p>\n

\u201cYou could have many quantum dots in an array, and this could be used to measure magnetic fields in living organisms, or to understand how the magnetic field is distributed in a material or a device,\u201d Velasco said.<\/p>\n

This story is adapted from material from the University of California, Santa Cruz<\/a>, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source<\/a>.<\/em><\/p>\n","protected":false},"excerpt":{"rendered":"

Physicist Jairo Velasco Jr (left) and graduate student Zhehao Ge (right) in Velasco\u2019s lab at<\/p>\n","protected":false},"author":1,"featured_media":43256,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"_links":{"self":[{"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/posts\/43254"}],"collection":[{"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/comments?post=43254"}],"version-history":[{"count":2,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/posts\/43254\/revisions"}],"predecessor-version":[{"id":43257,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/posts\/43254\/revisions\/43257"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/media\/43256"}],"wp:attachment":[{"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/media?parent=43254"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/categories?post=43254"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/peymantaeidi.net\/stem-cell\/wp-json\/wp\/v2\/tags?post=43254"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}