Tunneling into Ferromagnetic Quantum Hall States: Observation of a Spin Bottleneck

TL;DR

This study investigates electron tunneling into high mobility 2D electron systems in quantum Hall states, revealing a spin bottleneck caused by slow in-plane spin relaxation that affects tunneling rates.

Contribution

It uncovers a novel spin bottleneck phenomenon in tunneling into spin-polarized quantum Hall states, highlighting the role of spin relaxation dynamics.

Findings

Tunneling at most filling factors is characterized by a single rate.

In spin-polarized states, tunneling occurs at two distinct rates differing by up to 100 times.

The slow rate depends on temperature and barrier thickness, indicating a spin relaxation bottleneck.

Abstract

We explore the characteristics of equilibrium tunneling of electrons from a 3D electrode into a high mobility 2D electron system. For most 2D Landau level filling factors, we find that tunneling can be characterized by a single, well-defined tunneling rate. However, for spin-polarized quantum Hall states (nu = 1, 3 and 1/3) tunneling occurs at two distinct rates that differ by up to 2 orders of magnitude. The dependence of the two rates on temperature and tunnel barrier thickness suggests that slow in-plane spin relaxation creates a bottleneck for tunneling of electrons.