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Observation of the two-channel Kondo effect


Some of the most intriguing problems in solid-state physics arise when the motion of one electron dramatically affects the motion of surrounding electrons. Traditionally, such highly correlated electron systems have been studied mainly in materials with complex transition metal chemistry1,2. Over the past decade, researchers have learned to confine one or a few electrons within a nanometre-scale semiconductor ‘artificial atom’, and to understand and control this simple system in detail3. Here we combine artificial atoms to create a highly correlated electron system within a nano-engineered semiconductor structure3. We tune the system in situ through a quantum phase transition between two distinct states, each a version of the Kondo state4, in which a bound electron interacts with surrounding mobile electrons. The boundary between these competing Kondo states is a quantum critical point—namely, the exotic and previously elusive two-channel Kondo state5,6, in which electrons in two reservoirs are entangled through their interaction with a single localized spin.

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Figure 1: One and two-channel Kondo effects.
Figure 2: Artificial magnetic impurity.
Figure 3: The formation of two competing 1CK states with two different reservoirs.
Figure 4: Evidence for 2CK physics.

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We thank A. Schiller, E. Lebanon, F. Anders, I. Affleck, T. Costi, L. Glazman, K. Le Hur, C. Marcus, M. Pustilnik, E. Sela, J. von Delft and G. Zarand for discussions. E. Lebanon and F. Anders also performed NRG calculations that gave us crucial intuition regarding where our experimental system was in parameter space. S. Roy helped us understand how to perform nonlinear fits to determine the exponents α and α2 for the energy dependence in both 1CK and 2CK regimes. This work was supported by an NSF CAREER Award, a US-Israel BSF Award, DIP and ISF. D.G.-G. acknowledges Fellowships from the Sloan and Packard Foundations, and a Research Corporation Research Innovation Award. R.M.P. was supported by an ARO Graduate Fellowship during the early stages of this work.

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Correspondence to D. Goldhaber-Gordon.

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Supplementary information

Supplementary Discussion

This file contains Supplementary Discussion of data analysis and interpretation with brief mention of measurement techniques and relations to other proposed experimental two-channel Kondo systems. The file also contains Supplementary Figures S1-S7 with Legends and additional references. (PDF 382 kb)

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Potok, R., Rau, I., Shtrikman, H. et al. Observation of the two-channel Kondo effect. Nature 446, 167–171 (2007).

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