Two-channel Kondo effect and renormalization flow with macroscopic quantum charge states

• Autores: Z. Iftikhar, S. Jezouin, A. Anthore, U. Gennser, D. Parmentier, A. Cavanna, F. Pierre
• Localización: Nature: International weekly journal of science, ISSN 0028-0836, Vol. 526, Nº 7572, 2015, págs. 233-236
• Idioma: inglés
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• Resumen

  • Many-body correlations and macroscopic quantum behaviours are fascinating condensed matter problems. A powerful test-bed for the many-body concepts and methods is the Kondo effect1,2, which entails the coupling of a quantum impurity to a continuum of states. It is central in highly correlated systems3-5 and can be explored with tunable nanostructures6-9. Although Kondo physics is usually associated with the hybridization of itinerant electrons with microscopic magnetic moments10, theory predicts that it can arise whenever degenerate quantum states are coupled to a continuum4,11-14. Here we demonstrate the previously elusive ‘charge’ Kondo effect in a hybrid metal–semiconductor implementation of a single-electron transistor, with a quantum pseudospin of 1/2 constituted by two degenerate macroscopic charge states of a metallic island11,15-20. In contrast to other Kondo nanostructures, each conduction channel connecting the island to an electrode constitutes a distinct and fully tunable Kondo channel11, thereby providing unprecedented access to the two-channel Kondo effect and a clear path to multi-channel Kondo physics1,4,21,22. Using a weakly coupled probe, we find the renormalization flow, as temperature is reduced, of two Kondo channels competing to screen the charge pseudospin. This provides a direct view of how the predicted quantum phase transition develops across the symmetric quantum critical point4,21. Detuning the pseudospin away from degeneracy, we demonstrate, on a fully characterized device, quantitative agreement with the predictions for the finite-temperature crossover from quantum criticality17.