Excitonic Aharonov–Bohm Oscillations in Core–Shell Nanowires

Abstract

Phase coherence in nanostructures is at the heart of a wide range of quantum effects such as Josephson oscillations between exciton–polariton condensates in microcavities, conductance quantization in 1D ballistic transport, or the optical (excitonic) Aharonov–Bohm effect in semiconductor quantum rings. These effects only occur in structures of the highest perfection. The 2D semiconductor heterostructures required for the observation of Aharonov–Bohm oscillations have proved to be particularly demanding, since interface roughness or alloy fluctuations cause a loss of the spatial phase coherence of excitons, and ultimately induce exciton localization. Experimental work in this field has so far relied on either self‐assembled ring structures with very limited control of shape and dimension or on lithographically defined nanorings that suffer from the detrimental effects of free surfaces. Here, it is demonstrated that nanowires are an ideal platform for studies of the Aharonov–Bohm effect of neutral and charged excitons, as they facilitate the controlled fabrication of nearly ideal quantum rings by combining all‐binary radial heterostructures with axial crystal‐phase quantum structures. Thanks to the atomically flat interfaces and the absence of alloy disorder, excitonic phase coherence is preserved even in rings with circumferences as large as 200 nm.

Multiband k·p model and fitting scheme for ab initio based electronic structure parameters for wurtzite GaAs

“…The scope of our work is to provide a versatile tool that can generate parameter sets for k • p models of arbitrary complexity and level of sophistication including, but also going beyond, six or eight basis functions. We focus on WZ GaAs, as this material can be employed in novel nanowire-based crystal-phase heterostructures [18] and the description of its electronic structure requires the consideration of at least one additional conduction band [12,19].…”

Persistent spin textures and currents in wurtzite nanowire-based quantum structures

“…Other than traditional low-dimensional electron gases or quantum wires, the combination of different materials or the intrinsic Fermi-level pinning allows to built radial and axial heterostructures which form tubular or ringlike quantum systems. [57][58][59][60][61][62] The resulting potential landscape has shown to have large impact on the SOC. [63][64][65] At the same time, the special transport topology provides an ideal platform for testing spin and phase-coherent phenomena.…”

“…[63][64][65] At the same time, the special transport topology provides an ideal platform for testing spin and phase-coherent phenomena. [60][61][62]66 In this paper, we focus on the tubular and ring-shaped confinement geometry in wurtzite nanowires and explore the possibility to find spin-preserving symmetries. Taking into account the intrinsic SOC of the wurtzite lattice and the extrinsic SOC due to a radial potential asymmetry, we construct effective SOC Hamiltonians for the quasi-2D quantum tube and the quasi-1D quantum ring by projecting on the lowest radial and axial modes.…”

Оптические переходы и фотолюминесценция в цилиндрической ядро/слой/оболочка гетероструктуре beta-CdS/beta-HgS/beta-CdS

“…В приближении эффективной массы в работе [45] было проведено численное исследование экситонных состояний в цилиндрической структуре SiO 2 /Si/SiO 2 -квантовая точка-квантовая яма, показано влияние эффекта размерного квантования на энергию связи электронно-дырочной пары. В работе [46] было проведено исследование влияния нейтральных и заряженных экситонных состояний (трионов) на поведение осцилляций Ааронова−Бома в слоистой нанопроволоке. Одномерные экситонные состояния в цилиндрической ядро/слой/оболочка-струк туре CdS/HgS/CdS при сильном квантовании поперечного движения носителей рассмотрены в работе [39].…”