Field-tunable magnetic phases in a semiconductor-based two-dimensional Kondo lattice

Abstract

We show the existence of intrinsic localized spins in mesoscopic high-mobility GaAs/AlGaAs heterostructures. Non-equilibrium transport spectroscopy reveals a quasi-regular distribution of the spins, and indicates that the spins interact indirectly via the conduction electrons. The interaction between spins manifests in characteristic zero-bias anomaly near the Fermi energy, and indicates gate voltage-controllable magnetic phases in high-mobility heterostructures. To address this issue further, we have also designed electrostatically tunable Hall devices, that allow a probing of Hall characteristics at the active region of the mesoscopic devices. We show that the zero field Hall coefficient has an anomalous contribution, which can be attributed to scattering by the localized spins. The anomalous contribution can be destroyed by an increase in temperature, source drain bias, or field range.

Oscillatory Hall effect in high-mobility two-dimensional electron gases

“…An increase in n 2D , the field range to calculate ␥ H , or application of source-drain bias V SD decreases the amplitude of the oscillations. 20 The amplitude of these oscillations also decreases with increasing T ͑see small interaction parameter r s Ϸ 3 for the operating n 2D .…”

Effect of a perpendicular magnetic field on the zero-bias anomaly in two-dimensional electron systems

“…However, for several localized spins, indirect magnetic exchange interaction can set in, which is a nonlocal effect. 4,7,12 The exchange interaction between such spins with distance R from each other is mediated by Friedel oscillations. The nature and strength of the interaction J depends on the conductionelectron density and can be affected by B Ќ .…”