{"id":268,"date":"2014-01-29T18:58:58","date_gmt":"2014-01-29T18:58:58","guid":{"rendered":"http:\/\/www.icmm.csic.es\/tqe\/?page_id=268"},"modified":"2018-02-27T08:04:42","modified_gmt":"2018-02-27T08:04:42","slug":"superconducting-hybrids","status":"publish","type":"page","link":"https:\/\/wp.icmm.csic.es\/tqe\/research-interests\/superconducting-hybrids\/","title":{"rendered":"Superconducting hybrids"},"content":{"rendered":"
The hybrid combination of low dimensional semiconductors with superconductors offers a versatile ground for novel device concepts, such as supercurrent transistors, sources of spin-entangled electrons or nano-SQUIDS.<\/div>\n
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From a more basic point of view, these hybrid systems are interesting melting pots where various fundamental effects in condensed matter physics coexist. For example, when a quantum dot (QD) is coupled to a superconducting electrode (S) two very distinct phenomena compete. On one hand, superconductivity arises from the collective behaviour of a large number of electrons, while QDs usually act as quantum box with just a few electrons. In a superconductor the electrons feel a net attractive interaction that binds them into Cooper pairs, while electrons in a QD strongly repel each other. The underlying physics behind such hybrid device ultimately relies on the physics of the Anderson model where the standard metallic host is replaced by a superconducting one, namely the physics of a (quantum) magnetic impurity in a superconductor.<\/div>\n
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Magnetic impurities can profoundly modify the state of a metal. Well below the Kondo<\/a> temperature, the impurity is fully screened by quasiparticle exchange and the ground state is a Kondo<\/a> singlet. In a superconductor, however, no quasiparticles are available below the superconducting gap, hence Kondo<\/a> screening is incomplete. In general, a quantum impurity in a superconductor is a complex system where two many-body states, a magnetic doublet and a singlet, compete in becoming the GS. As a result, the system undergoes a<\/div>\n

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quantum phase transition (QPT) when the superconduting gap is of the order of the Kondo<\/a> temperature. A characteristic feature is the the emergence of sub-gap bound states, the so-called Yu-Shiba-Rusinov (YRS) states. Across the QPT the GS switches fermion parity and spin. Accordingly, YRS states crossing zero energy also signal a parity-changing QPT.<\/div>\n

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Experimentally, parity crossings are marked by zero bias anomalies (ZBA)s in transport though the QD. Interestingly, ZBAs in similar hybrid devices based on semiconducting nanowires with strong spin-orbit coupling are a strong signature of emergent Majorana<\/a> bound states.<\/div>\n
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The study of all these coexisting phenomena in hybrid nanostructures is one of the most exciting and challenging topics in modern condensed matter physics.<\/div>\n","protected":false},"excerpt":{"rendered":"

The hybrid combination of low dimensional semiconductors with superconductors offers a versatile ground for novel device concepts, such as supercurrent transistors, sources of spin-entangled electrons or nano-SQUIDS.   From a more basic point of view, these hybrid systems are interesting melting pots where various fundamental effects in condensed matter physics coexist. For example, when a … Continue reading Superconducting hybrids<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":18,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-268","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/pages\/268","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/comments?post=268"}],"version-history":[{"count":1,"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/pages\/268\/revisions"}],"predecessor-version":[{"id":1011,"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/pages\/268\/revisions\/1011"}],"up":[{"embeddable":true,"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/pages\/18"}],"wp:attachment":[{"href":"https:\/\/wp.icmm.csic.es\/tqe\/wp-json\/wp\/v2\/media?parent=268"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}