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Evidence of Kondo Screening Cloud of Micron Lengths
January 26, 20213:30 pm – 4:30 pm (CDT)

Evidence of Kondo Screening Cloud of Micron Lengths


Ivan Borzenets (City University of Hong Kong)

Event Details

The Kondo effect, known as the archetype of many-body correlations, arises from the interaction between a localized magnetic moment and surrounding conducting electrons. Advances of nanotechnology allow us to study the Kondo effect for a single magnetic impurity confined in a semiconductor quantum dot in contact with electron reservoirs. This development also makes it possible to embed a Kondo correlated state into an interferometer. Although the Kondo effect is now a text-book subject of many-body physics, detection of its key object, the Kondo cloud, remained elusive despite many attempts for the past 50 years. In this work, we present experimental evidence of a Kondo cloud extending over a length of micrometers comparable to the theoretical length ξK. Our measurement scheme involves, a Kondo impurity formed in a quantum dot (QD), and coupled to a quasi- one dimensional channel that houses a Fabry-Perot (FP) interferometer of variable length L > 1 μm. When we tune a gate voltage applied to the interferometer end distant from the QD by the length L, we observe oscillations in measured Kondo temperature: a sign of the cloud at distance L. Our experiment shows that the Kondo cloud has the main body of size larger than one micrometer with a tail extending further: in good agreement with our theoretical calculation. This provides essential insight into the fundamental phenomenon of spin screening in a metal, and opens up a way of engineering the spin screening and the entanglement.

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