Design of a Two Channel Kondo Interferometer

The transmission phase of electrons passing through a quantum dot gives insight into the many-body state of the mesoscopic system the dot is a part of. When coupled to a reservoir, the impurity spin is screened and a Kondo singlet is formed. This Kondo state scatters electrons, inducing a π/2 transmission phase shift, which was recently measured [1,2]. When an impurity is equally coupled to two reservoirs, the over-screening of the impurity leads to non-Fermi liquid behavior [3]. This two-channel Kondo state does not scatter electrons into one single particle state, but into an infinite number of such states, each with zero amplitude. Thus, a well-defined transmission phase might not be expected. However, it has been suggested that coherent transport of a new type of low-energy excitations can still produce a measurable phase shift [4]. We discuss design and preliminary implementation of a quantum dot device to measure the phase signature across a two-channel Kondo state.

[1] M. Zaffalon, et al., Phys. Rev. Lett. 100, 226601 (2008)
[2] S. Takada et al., Phys. Rev. Lett. 113, 126601 (2014)
[3] A. Keller et al., Nature. 526, 15261 (2015)
[4] A. Carmi et al., Phys. Rev. B. 86, 115129 (2012)