Kondo effect in f-electron superlattices

TL;DR

This paper investigates how the Kondo effect influences electronic properties in f-electron superlattices, revealing resonance phenomena, structural dependence, and anisotropic conductivity changes related to the Kondo insulating state.

Contribution

It demonstrates the role of the Kondo effect in modifying the density of states and transport properties in f-electron superlattices, highlighting interference effects and anisotropy.

Findings

Resonances at the Fermi energy depend on superlattice structure.

Insertion of Kondo lattice layers alters the Kondo insulator gap to a pseudo gap.

Superlattices become strongly anisotropic below the Kondo temperature.

Abstract

We demonstrate the importance of the Kondo effect in artificially created {\it f}-electron superlattices. We show that the Kondo effect does not only change the density of states of the {\it f}-electron layers, but is also the cause of pronounced resonances at the Fermi energy in the density of states of the non-interacting layers in the superlattice, which are between the {\it f}-electron layers. Remarkably, these resonances strongly depend on the structure of the superlattice; due to interference, the density of states at the Fermi energy can be strongly enhanced or even shows no changes at all. Furthermore, we show that by inserting the Kondo lattice layer into a three-dimensional (3D) metal, the gap of the Kondo insulating state changes from a full gap to a pseudo gap with quadratically vanishing spectral weight around the Fermi energy. Due to the formation of the Kondo insulating state in the {\it f}-electron layer, the superlattice becomes strongly anisotropic below the Kondo temperature. We prove this by calculating the in-plane and out-of-plane conductivity of the superlattice.