Phase coherent transport in (Ga,Mn)As

Abstract

Quantum interference effects and resulting quantum corrections of the conductivity have been intensively studied in disordered conductors over the last decades. The knowledge of phase coherence lengths and underlying dephasing mechanisms are crucial to understand quantum corrections to the resistivity in the different material systems. Due to the internal magnetic field and the associated breaking of timereversal symmetry quantum interference effects in ferromagnetic materials have been scarcely explored. Below we describe the investigation of phase coherent transport phenomena in the newly discovered ferromagnetic semiconductor (Ga,Mn)As. We explore universal conductance fluctuations in mesoscopic (Ga,Mn)As wires and rings, the Aharonov-Bohm effect in nanoscale rings and weak localization in arrays of wires, made of the ferromagnetic semiconductor material. The experiments allow to probe the phase coherence length L φ and the spin flip length L SO as well as the temperature dependence of dephasing.

Magnetic ordering effects in a Mn-modulation-doped high mobility two-dimensional hole system

“…10͒ have been reported. A lot of intriguing properties such as magnetic anisotropies 11 and their device application potential 12 as well as quantum interference effects 13 have been explored based on these disordered magnetic conductors.…”

Quantum transport in ferromagnetic permalloy nanostructures

“…In ferromagnetic ͑Ga,Mn͒As wires the phase coherence length followed a T −0.5 dependency 21,22 and was associated with critical electron-electron scattering ͑CEEI͒. 21,25,26 For permalloy CEEI seems not to be a suitable candidate for dephasing as CEEI describes dephasing in a strongly disordered metal near the metal-insulator transition ͑MIT͒. In metals far away from the MIT dephasing is usually ascribed to Nyquist scattering leading to a phase coherence length ϰT −1/3 in 1D systems.…”

Origin of negative magnetoresistance of GaAs/(Ga,Mn)As core-shell nanowires

“…Typically high quality (Ga,Mn)As has an about three times larger saturation magnetization of ~37 mT. 29 We note, however, that also the uniaxial anisotropy constant 8500 U K  J/m 3 is very high, when compared to etched nanowires, for which K U usually does not exceed 1500 J/m 3 . 26 might be a consequence of the peculiar strain and strainrelaxation pattern associated with the core-shell geometry.…”