Local Kondo temperatures in atomic chains

Abstract

We study the effect of disorder in strongly interacting small atomic chains. Using the Kotliar-Ruckenstein slave-boson approach, we diagonalize the Hamiltonian via scattering matrix theory. We numerically solve the Kondo transmission and the slave-boson parameters that allow us to calculate the Kondo temperature. We demonstrate that in the weak disorder regime, disorder in the energy levels of the dopants induces a nonscreened disorder in the Kondo couplings of the atoms. We show that disorder increases the Kondo temperature of a perfect chain. We find that this disorder in the couplings comes from a local distribution of Kondo temperatures along the chain. We propose two experimental setups where the impact of local Kondo temperatures can be observed. Electron-electron interactions, disorder, and localization are among the most studied phenomena in condensed matter physics. In one-dimensional (1D) systems, disorder and interactions play an important role in transport. In the limiting case of no electron-electron interactions (U = 0), we encounter Anderson localization for even the smallest disorder [1,2]. When interactions dominate, the system is in a Mott insulator state [2,3]. Both limiting cases have been extensively studied, but much less is known in the intermediate regime. of intermediate strength can screen disorder, and a metallic phase has been predicted in this regime [8]. Partial disorder screening gives a gapless two-fluid phase where a fraction of electrons undergo Mott localization and the rest are Anderson localized [8].Recently it has been argued that Kondo physics can play an important role in the conductance of short 1D constrictions. Friedel oscillations are thought to assist the localization of one or more electrons in these short channels. In particular, the so-called 0.7 anomaly and the zero bias anomaly in quantum point contacts have been attributed to the Kondo effect in these spontaneously localized charges [9,10].This Rapid Communication presents a theoretical model for investigating the electron-electron interactions and disorder on Kondo transport through a spin chain with intermediate interaction strength connected on its endpoints to two reservoirs. In this intermediate electron-electron interaction strength regime we do not expect the indirect magnetic exchange to play a significant role in Kondo transport. For stronger interactions (weaker couplings) nontrivial competition between the Ruderman-Kittel-Kasuya-Yosida coupling and the Kondo effect is predicted to appear [11]. We show that Coulomb interactions screen the disorder potential for weak disorder and therefore the Kondo transmission increases with increasing interactions. We demonstrate that the screened disorder potential induces a nonscreened disorder in the coupling between the electron spin in the atoms and the conduction electrons, the Kondo coupling. This disorder in the Kondo couplings is due to different local Kondo temperatures in the chain. In particular, we find that disorder can enhance local Kondo couplings an...

Quantum simulation of the Hubbard model with dopant atoms in silicon

“…Strain could be used to further enhance the splitting between light and heavy holes, or suppress valley interference processes of electrons 31,46 . Interestingly, open Hubbard systems which may exhibit unusual Kondo behaviour 47,48 could also be studied by this method. The demonstrated measurement of spectral functions could be used to directly determine excitation spectra, evaluate correlation functions 45 , or obtain quasiparticle interference spectra 17 , all of which contain rich information about many-body states, including chargeordering effects.…”