Excitonic Aharonov–Bohm Oscillations in Core–Shell Nanowires

One of the most demanding challenges for materials synthesis is the fabrication of nanostructures that enable the observation of quantum phase coherence phenomena. A prominent example is the excitonic Aharonov-Bohm effect, which requires nanoscale semiconductor rings with the highest structural perfection. Here, we exploit the three-dimensional nature of GaAs-based core-shell nanowires and realize near-ideal quantum rings. Thanks to the atomically flat interfaces and the absence of alloy disorder, excitonic phase coherence is preserved and we observe Aharonov-Bohm oscillations of both neutral and charged excitons (trions) in rings with circumferences as large as 200 nm.

Top, left: Cross-sectional view of the GaAs/AlAs core/shell structure along the nanowire axis. Top, right: Simulated electron and hole charge densities in the quantum ring formed by the GaAs shell quantum well and an axial twin boundary. Bottom: Aharonov-Bohm oscillations of the transition energy of the exciton confined in the quantum ring.

The Aharonov-Bohm effect results from the phase shift acquired by an electronic excitation in a ring threaded by a magnetic field, and is in essence a property of charged particles. However, the effect also occurs for neutral excitons in semiconductor quantum rings if they exhibit a radial polarization. In our case, the polarization of quantum ring excitons can be tuned to the desired degree by a controlled p-type doping of the nanowire core. Moreover, we fabricate rings with nearly ideal interfaces by combining all-binary radial compositional heterostructures with crystal-phase quantum wells along the axis of the nanowires. The exceptionally large coherence length of 200 nm demonstrates that GaAs/AlAs core-shell nanowires are an ideal platform for the study of phase-coherence effects of excitons. Besides the high structural perfection required for preserving spatial phase coherence, these nanostructures also offer a high degree of control over the quantum ring dimensions and the exciton polarization, and thus pave the way toward wavefunction engineering in three dimensions for the experimental study of coherent excitations in semiconductors.

1 Author P. Corfdir , O. Marquardt , R. B. Lewis , C. Sinito , M. Ramsteiner , A. Trampert , U. Jahn , L. Geelhaar , O. Brandt , V. M. Fomin

Excitonic Aharonov-Bohm oscillations in core-shell nanowires

Source Adv. Mater. , 31 , 1805645 ( 2019 )
DOI : 10.1002/adma.201805645 | 3041 Cite : Bibtex RIS
P. Corfdir, O. Marquardt, R. B. Lewis, C. Sinito, M. Ramsteiner, A. Trampert, U. Jahn, L. Geelhaar, O. Brandt, and V. M. Fomin