Editing Kondo effect (section)

== Examples ==
Extended to a lattice of magnetic ions, the Kondo effect likely explains the formation of [[heavy fermion]]s and [[Kondo insulator]]s in intermetallic compounds, especially those involving rare earth elements such as [[cerium]], [[praseodymium]], and [[ytterbium]], and actinide elements such as [[uranium]]. In [[heavy fermion]] materials, the non-perturbative growth of the interaction leads to quasi-electrons with masses up to thousands of times the free electron mass, i.e., the electrons are dramatically slowed by the interactions. In a number of instances they are [[superconductors]]. It is believed that a manifestation of the Kondo effect is necessary for understanding the unusual metallic delta-phase of [[plutonium]].{{Citation needed|date=April 2020}}

The Kondo effect has been observed in [[quantum dot]] systems.<ref>{{cite journal|doi=10.1126/science.281.5376.540|pmid=9677192|first=Sara M.|last=Cronenwett|date=1998 |title=A Tunable Kondo Effect in Quantum Dots|journal=Science|volume=281|number=5376|pages=540–544|arxiv = cond-mat/9804211 |bibcode = 1998Sci...281..540C |s2cid=5139144}}</ref><ref>{{Cite journal|url=http://kouwenhovenlab.tudelft.nl/wp-content/uploads/2011/10/97-revival-of-the-kondo.pdf|title=Revival of the Kondo|access-date=2016-08-19|archive-date=2017-05-17|archive-url=https://web.archive.org/web/20170517124645/http://kouwenhovenlab.tudelft.nl/wp-content/uploads/2011/10/97-revival-of-the-kondo.pdf|url-status=dead}}</ref> In such systems, a quantum dot with at least one unpaired electron behaves as a magnetic impurity, and when the dot is coupled to a metallic conduction band, the conduction electrons can scatter off the dot. This is completely analogous to the more traditional case of a magnetic impurity in a metal.

Band-structure hybridization and flat band topology in Kondo insulators have been imaged in [[angle-resolved photoemission spectroscopy]] experiments.<ref>{{Cite journal|last1=Neupane|first1=Madhab|last2=Alidoust|first2=Nasser|last3=Belopolski|first3=Ilya|last4=Bian|first4=Guang|last5=Xu|first5=Su-Yang|last6=Kim|first6=Dae-Jeong|last7=Shibayev|first7=Pavel P.|last8=Sanchez|first8=Daniel S.|last9=Zheng|first9=Hao|last10=Chang|first10=Tay-Rong|last11=Jeng|first11=Horng-Tay|display-authors=etal|date=2015-09-18|title=Fermi surface topology and hot spot distribution in the Kondo lattice system CeB<sub>6</sub>|journal=Physical Review B|volume=92|issue=10|pages=104420|doi=10.1103/PhysRevB.92.104420|arxiv=1411.0302|bibcode=2015PhRvB..92j4420N|doi-access=free}}</ref><ref>{{Cite journal|last1=Neupane|first1=M.|last2=Alidoust|first2=N.|last3=Xu|first3=S.-Y.|last4=Kondo|first4=T.|last5=Ishida|first5=Y.|last6=Kim|first6=D. J.|last7=Liu|first7=Chang|last8=Belopolski|first8=I.|last9=Jo|first9=Y. J.|last10=Chang|first10=T.-R.|last11=Jeng|first11=H.-T.|date=2013|title=Surface electronic structure of the topological Kondo-insulator candidate correlated electron system SmB<sub>6</sub>|journal=Nature Communications|language=en|volume=4|issue=1|page=2991|doi=10.1038/ncomms3991|pmid=24346502|arxiv=1312.1979|bibcode=2013NatCo...4.2991N|issn=2041-1723|doi-access=free}}</ref><ref>{{Citation|last1=Hasan|first1=M. Zahid|title=Topological Insulators, Topological Dirac semimetals, Topological Crystalline Insulators, and Topological Kondo Insulators|date=2015|url=https://onlinelibrary.wiley.com/doi/abs/10.1002/9783527681594.ch4|work=Topological Insulators|pages=55–100|publisher=John Wiley & Sons, Ltd.|language=en|doi=10.1002/9783527681594.ch4|isbn=978-3-527-68159-4|access-date=2020-04-26|last2=Xu|first2=Su-Yang|last3=Neupane|first3=Madhab|url-access=subscription}}</ref>

In 2012, Beri and Cooper proposed a topological Kondo effect could be found with [[Majorana fermion]]s,<ref>{{Cite journal|last1=Béri|first1=B.|last2=Cooper|first2=N. R.|year=2012|title=Topological Kondo Effect with Majorana Fermions|journal=Physical Review Letters|volume=109|issue=15|pages=156803|doi=10.1103/PhysRevLett.109.156803|pmid=23102351|arxiv=1206.2224|bibcode=2012PhRvL.109o6803B|s2cid=45712589}}</ref> while it has been shown that [[Quantum simulator|quantum simulations]] with [[ultracold atom]]s may also demonstrate the effect.<ref>{{Cite journal|last1=Buccheri|first1=F.|last2=Bruce|first2=G. D.|last3=Trombettoni|first3=A.|last4=Cassettari|first4=D.|last5=Babujian|first5=H.|last6=Korepin|first6=V. E.|last7=Sodano|first7=P.|date=2016-01-01|title=Holographic optical traps for atom-based topological Kondo devices|journal=New Journal of Physics|language=en|volume=18|issue=7|pages=075012|doi=10.1088/1367-2630/18/7/075012|issn=1367-2630|arxiv=1511.06574|bibcode=2016NJPh...18g5012B|s2cid=118610269}}</ref>

In 2017, teams from the Vienna University of Technology and Rice University conducted experiments into the development of new materials made from the metals cerium, bismuth and palladium in specific combinations and theoretical work experimenting with models of such structures, respectively. The results of the experiments were published in December 2017<ref>{{Cite journal|last1=Dzsaber|first1=S.|last2=Prochaska|first2=L.|last3=Sidorenko|first3=A.|last4=Eguchi|first4=G.|last5=Svagera|first5=R.|last6=Waas|first6=M.|last7=Prokofiev|first7=A.|last8=Si|first8=Q.|last9=Paschen|first9=S.|date=2017-06-16|title=Kondo Insulator to Semimetal Transformation Tuned by Spin-Orbit Coupling|journal=Physical Review Letters|language=en|volume=118|issue=24|pages=246601|doi=10.1103/PhysRevLett.118.246601|pmid=28665644|arxiv=1612.03972|bibcode=2017PhRvL.118x6601D|issn=0031-9007|doi-access=free}}</ref> and, together with the theoretical work,<ref>{{Cite journal|last1=Lai|first1=H.H.|last2=Grefe|first2=S.E.|last3=Paschen|first3=S.|last4=Si|first4=Q.|year=2012|title=Weyl–Kondo semimetal in heavy-fermion systems|journal=Proceedings of the National Academy of Sciences of the United States of America |volume=115|issue=1|pages=93–97|doi=10.1073/pnas.1715851115|pmid=29255021|pmc=5776817|arxiv=1206.2224|bibcode=2018PNAS..115...93L|doi-access=free}}</ref> lead to the discovery of a new state,<ref>Gabbatiss, J. (2017) [https://www.independent.co.uk/news/science/quantum-material-physics-weyl-kondo-semimetal-vienna-university-technology-a8121141.html "Scientists discover entirely new material that cannot be explained by classical physics"], ''The Independent''</ref> a correlation-driven [[Weyl semimetal]]. The team dubbed this new [[quantum material]] Weyl-Kondo [[semimetal]].