{"id":7210,"date":"2022-05-05T19:05:31","date_gmt":"2022-05-05T18:05:31","guid":{"rendered":"https:\/\/telecomkh.info\/?p=7210"},"modified":"2022-06-21T19:08:01","modified_gmt":"2022-06-21T18:08:01","slug":"discovery-of-the-one-way-superconductor-thought-to-be-impossible","status":"publish","type":"post","link":"https:\/\/telecomkh.info\/?p=7210","title":{"rendered":"Discovery of the one-way superconductor, thought to be impossible"},"content":{"rendered":"

Associate Professor Mazhar Ali and his research group at TU Delft have discovered one-way superconductivity without magnetic fields, something that was thought to be impossible ever since its discovery in 1911 \u2013 up till now. The discovery, which was published in Nature, makes use of 2D quantum materials and paves the way towards superconducting computing. Superconductors can make electronics hundreds of times faster, all with zero energy loss. Ali: \u201cIf the 20th century was the century of semi-conductors, the 21st can become the century of the superconductor.\u201d<\/strong><\/p>\n

 <\/p>\n

By TU Delft<\/em><\/span><\/p>\n

During the 20th century many scientists, including Nobel Prize winners, have puzzled over the nature of superconductivity, which was discovered by Dutch physicist Kamerlingh Onnes in 1911 (read more about this in the frame below). In superconductors, a current goes through a wire without any resistance, which means inhibiting this current or even blocking it is hardly possible \u2013 let alone getting the current to flow only one way and not the other. That Dr. Heng Wu and Dr. Yaojia Wang, the lead researchers in Ali\u2019s group who carried out this study, managed to make superconducting one-directional \u2013 necessary for computing \u2013 is remarkable: one can compare it to inventing a special type of ice which gives you zero friction when skating one way, but insurmountable friction the other way.<\/p>\n

Superconductor: super-fast, super-green<\/strong>
\nThe advantages of applying superconductors to electronics are twofold. Superconductors can make electronics hundreds of times faster, and implementing superconductors into our daily lives would make IT much greener: if you were to spin a superconducting wire from here to the moon, it would transport the energy without any loss. For instance, the use of superconductors instead of regular semi-conductors might safe up to 10% of all western energy reserves according to NWO. An interview with Associate Professor Mazhar Ali on the paper that establishes proof-of-concept, \u201cThe field-free Josephson diode in a van der Waals heterostructure\u00bb:<\/p>\n

Q: Why, when one-way direction works with normal semi-conduction, has one-way superconductivity never worked before?<\/strong>
\nA: Mazhar Ali: \u201cElectrical conduction in semiconductors, like Si, can be one-way because of a fixed internal electric dipole, so a net built in potential they can have. The textbook example is the famous \u00abpn junction\u00bb; where we slap together two semiconductors: one has extra electrons (-) and the other has extra holes (+). The separation of charge makes a net built in potential that an electron flying through the system will feel. This breaks symmetry and can result in \u00abone-way\u00bb properties because forward vs backwards, for example, are no longer the same. There is a difference in going in the same direction as the dipole vs going against it; similar to if you were swimming with the river or swimming up the river.\u201d
\n\u201cSuperconductors never had an analog of this one-directional idea without magnetic field; since they are more related to metals (i.e. conductors, as the name says) than semiconductors, which always conduct in both directions and don’t have any built in potential. Similarly, Josephson Junctions (JJs), which are sandwiches of two superconductors with non-superconducting, classical barrier materials in-between the superconductors, also haven’t had any particular symmetry-breaking mechanism that resulted in a difference between \u00abforward\u00bb and \u00abbackwards\u00bb.<\/p>\n

Q: How did you manage to do what first seemed impossible?<\/strong>
\nA: \u201cIt was really the result of one of my group’s fundamental research directions. In what we call \u00abQuantum Material Josephson Junctions\u00bb (QMJJs), we replace the classical barrier material in JJs with a quantum material barrier, where the quantum material’s intrinsic properties can modulate the coupling between the two superconductors in novel ways. The Josephson Diode was an example of this: we used the quantum material Nb3Br8, which is a 2D material like graphene that has been theorized to host a net electric dipole, as our quantum material barrier of choice and placed it between two superconductors.\u201d
\n\u201cWe were able to peel off just a couple atomic layers of this Nb3Br8 and make a very, very thin sandwich – just a few atomic layers thick – which was needed for making the Josephson diode, and was not possible with normal 3D materials. Nb3Br8, is part of a group of new quantum materials being developed by our collaborators, Professor Tyrel McQueen\u2019s and his group at Johns Hopkins University in the USA, and was a key piece in us realizing the Josephson diode for the first time.\u201d<\/p>\n

Q: What does this discovery mean in terms of impact and applications?<\/strong>
\nA: \u201cMany technologies are based on old versions of JJ superconductors, for example MRI technology. Also, quantum computing today is based on Josephson Junctions. Technology which was previously only possible using semi-conductors can now potentially be made with superconductors using this building block. This includes faster computers, as in computers with up to terahertz speed, which is 300 to 400 times faster than the computers we are now using. This will influence all sorts of societal and technological applications. If the 20th century was the century of semi-conductors, the 21st can become the century of the superconductor.\u201d
\n\u201cThe first research direction we have to tackle for commercial application is raising the operating temperature. Here we used a very simple superconductor that limited the operating temperature. Now we want to work with the known so-called \u00abHigh Tc Superconductors\u00bb, and see whether we can operate Josephson diodes at temperatures above 77 K, since this will allow for liquid nitrogen cooling. The second thing to tackle is scaling of production. While it\u2019s great that we proved this works in nanodevices, we only made a handful. The next step will be to investigate how to scale production to millions of Josephson diodes on a chip.\u201d<\/p>\n

Q: How sure are you of your case?<\/strong>
\nA: \u201cThere are several steps which all scientists need to take to maintain scientific rigor. The first is to make sure their results are repeatable. In this case we made many devices, from scratch, with different batches of materials, and found the same properties every time, even when measured on different machines in different countries by different people. This told us that the Josephson diode result was coming from our combination of materials and not some spurious result of dirt, geometry, machine or user error or interpretation.\u201d
\n\u201cWe also carried out \u00absmoking gun\u00bb experiments that dramatically narrows the possibility for interpretation. In this case, to be sure that we had a superconducting diode effect we actually tried \u00abswitching\u00bb the diode; as in we applied the same magnitude of current in both forward and reverse directions and showed that we actually measured no resistance (superconductivity) in one direction and real resistance (normal conductivity) in the other direction.\u201d
\n\u201cWe also measured this effect while applying magnetic fields of different magnitudes and showed that the effect was clearly present at 0 applied field and gets killed by an applied field. This is also a smoking gun for our claim of having a superconducting diode effect at zero-applied field, a very important point for technological applications. This is because magnetic fields at the nanometer scale are very difficult to control and limit, so for practical applications, it is generally desired to operate without requiring local magnetic fields.\u201d<\/p>\n

Q: Is it realistic for ordinary computers (or even the supercomputers of KNMI and IBM) to make use of superconducting?<\/strong>
\nA: Yes it is! Not for people at home, but for server farms or for supercomputers, it would be smart to implement this. Centralized computation is really how the world works now-a-days. Any and all intensive computation is done at centralized facilities where localization adds huge benefits in terms of power management, heat management, etc. The existing infrastructure could be adapted without too much cost to work with Josephson diode based electronics. There is a very real chance, if the challenges discussed in the other question are overcome, that this will revolutionize centralized and supercomputing!\u201d<\/p>\n

On May 18th \u2013 19th, Associate Professor Mazhar Ali and his collaborators Prof. Valla Fatemi (Cornell University) and Dr. Heng Wu (TU Delft) are hosting a \u201cSuperconducting Diode Effects Workshop\u201d on the Virtual Science Forum, in which 12 international experts in the field will be giving recorded talks online (to be published on YouTube) about the current state of the field as well as future research and development directions.
\nAssociate Professor Mazhar Ali studied at UC Berkeley and Princeton and did his postdoc at IBM and won the Sofia Kovalevskaja Award from the Alexander von Humboldt Foundation in Germany before joining the faculty of Applied Sciences in Delft.<\/p>\n

Above, associate Prof. Dr. Mazhar Ali (middle) with his fellow researchers Dr. Yaojia Wang (left) and Dr. Heng Wu (right). \/ Image credited to TU Delft<\/em><\/span><\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Associate Professor Mazhar Ali and his research group at TU Delft have discovered one-way superconductivity without magnetic fields, something that was thought to be impossible ever since its discovery in 1911 \u2013 up till now. The discovery, which was published in Nature, makes use of 2D quantum materials and paves the way towards superconducting computing. … <\/p>\n

Continue reading \u00abDiscovery of the one-way superconductor, thought to be impossible\u00bb<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":7211,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[41,69],"tags":[],"_links":{"self":[{"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/posts\/7210"}],"collection":[{"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/telecomkh.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=7210"}],"version-history":[{"count":1,"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/posts\/7210\/revisions"}],"predecessor-version":[{"id":7212,"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/posts\/7210\/revisions\/7212"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/telecomkh.info\/index.php?rest_route=\/wp\/v2\/media\/7211"}],"wp:attachment":[{"href":"https:\/\/telecomkh.info\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=7210"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/telecomkh.info\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=7210"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/telecomkh.info\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=7210"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}