# Abrupt disappearance and reemergence of the SU(2) and SU(4) Kondo effects due to population inversion

## TL;DR

This paper predicts a repeated pattern of disappearance and reemergence of SU(2) and SU(4) Kondo effects in quantum dots due to population inversion, supported by analytical and numerical methods.

## Contribution

It introduces the novel prediction of abrupt Kondo effect transitions caused by level occupation switching in quantum dots.

## Key findings

- Recurrent disappearance and reemergence of Kondo effects with gate voltage.
- Level occupation switching explains the phenomenon.
- Numerical and analytical methods validate the predictions.

## Abstract

The interplay of almost degenerate levels in quantum dots and molecular junctions with possibly different couplings to the reservoirs has lead to many observable phenomena, such as the Fano effect, transmission phase slips and the SU(4) Kondo effect. Here we predict a dramatic repeated disappearance and reemergence of the SU(4) and anomalous SU(2) Kondo effects with increasing gate voltage. This phenomenon is attributed to the level occupation switching which has been previously invoked to explain the universal transmission phase slips in the conductance through a quantum dot. We use analytical arguments and numerical renormalization group calculations to explain the observations and discuss their experimental relevance and dependence on the physical parameters.