Inelastic electron scattering off a quantum dot in the cotunneling regime: the signature of mesoscopic Stoner instability

TL;DR

This paper investigates inelastic electron scattering in quantum dots near the mesoscopic Stoner instability, revealing unique signatures due to many-body states and tunneling correlations, which differ from magnetic impurities and explain experimental observations.

Contribution

It provides a theoretical analysis of inelastic scattering signatures in quantum dots close to the Stoner instability, highlighting differences from magnetic impurities and connecting to experimental findings.

Findings

Inelastic scattering cross section differs from magnetic impurity case at low temperatures.

Presence of low-lying many-body states affects scattering behavior.

Results explain the absence of dephasing rate saturation in recent experiments.

Abstract

We explore the inelastic electron scattering cross section off a quantum dot close to the Stoner instability. We focus on the regime of strong Coulomb blockade in which the scattering cross section is dominated by the cotunneling processes. For large enough exchange interaction the quantum dot acquires a finite total spin in the ground state. In this, so-called mesoscopic Stoner instability, regime we find that at low enough temperatures the inelastic scattering cross section (including the contribution due to an elastic electron spin-flip) for an electron with a low energy with respect to the chemical potential is different from the case of a magnetic impurity with the same spin. This difference stems from (i) presence of a low-lying many-body states of a quantum dot and (ii) the correlations of the tunneling amplitudes. Our results provide a possible explanation for absence of the dephasing rate saturation at low temperatures in recent experiment [N. Teneh, A. Yu. Kuntsevich, V. M. Pudalov, and M. Reznikov, Phys. Rev. Lett. 109, 226403 (2012)] in which existence of local spin droplets in disordered electron liquid has been unraveled.