Charge Fractionalization in the Two-Channel Kondo Effect

Abstract

The phenomenon of charge fractionalization describes the emergence of novel excitations with fractional quantum numbers, as predicted in strongly correlated systems such as spin liquids. We elucidate that precisely such an unusual effect may occur in the simplest possible non-Fermi liquid, the two-channel Kondo effect. To bring this concept down to experimental test, we study nonequilibrium transport through a device realizing the charge two-channel Kondo critical point in a recent experiment by Iftikhar et al. [Nature (London) 526, 233 (2015)NATUAS0028-083610.1038/nature15384]. The shot noise at low voltages is predicted to result in a universal Fano factor e^{*}/e=1/2. This allows us to experimentally identify elementary transport processes of emergent fermions carrying half-integer charge.

Tunable quantum criticality and super-ballistic transport in a “charge” Kondo circuit

“…Note the difference with the conductance in previous spin 2CK implementations with small quantum dots, where the naively expected √ T was predicted and observed [2,5]. Indeed, the conductance in these spin Kondo devices is proportional to the single-particle T matrix [16], whereas in the 'charge' implementation it relates to two-particle correlation functions (see [35] and also [43,45], or Eq. S10).…”

“…S10). After submission of this manuscript, three new works calculating the 2CK power law dependence of the conductance in the 'charge' Kondo implementation with different methods appeared (see [35] and also [43,45]) : a linear behavior is also found in [35] and [43,45] (a different T 2 scaling initially obtained in the published article [45] was subsequently corrected in an Erratum and also in the second arXiv version). For 3CK (N = 3), the naively expected T 2/5 is precisely reproduced by the new NRG calculation of the universal 'charge' Kondo conductance curve shown Fig.…”

Electric and heat transport in two-channel Kondo systems

“…when approaching the local moment fixed point from below, where the dots contain all higher order terms in products of λ 2 and T /T K . This agrees with the results from previous research [72][73][74]. Note that the full linear term in T /T K is by itself a series in λ 2 , while λ is not necessarily small.…”

Linear and non-linear transport properties of quantum-dot devices

“…In 1964, J. Kondo showed that, at low temperatures, the spin-flip scattering of the itinerant electron by the magnetic impurities enhances the electronical resistivity of metals. 4,53 Straightforward generalizations of this model allowed investigation of phase transitions, 54,55 fractional excitations 56,57 and non-Fermi liquid behavior. 51,52 For example, in multi-impurity problems, the competition between the antiferromagnetic coupling among the local moments and Kondo screening generates a quantum phase transition between a magnetic and non-magnetic phase.…”

“…In particular, the two-channel Kondo model displays a quantum phase transition from a Fermi liquid to non-Fermi liquid phase, driven by asymmetry between the couplings, and fractional excitation associated with Majorana quasi-particles. [56][57][58] The development nanostructure fabrication has allowed the realization of manybody physics in a well-controllable platform. One example is the observation of the Kondo effect in quantum dot devices.…”