A light-hole exciton in a quantum dot

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Abstract

A light-hole exciton is a quasiparticle formed from a single electron bound to a single light hole. This type of fundamental excitation, if confined inside a semiconductor quantum dot, could be advantageous in quantum information science and technology. However, it has been difficult to access it so far, because confinement and strain in conventional quantum dots favour a ground-state single-particle hole with a predominantly heavy-hole character. Here we demonstrate the creation of a light-hole exciton ground state by applying elastic stress to an initially unstrained quantum dot. Its signature is clearly distinct from that of the well-known heavy-hole exciton and consists of three orthogonally polarized bright optical transitions and a fine-structure splitting of hundreds of microelectronvolts between in-plane and out-of-plane components. This work paves the way for the exploration of the fundamental properties and of the potential relevance of three-dimensionally confined light-hole states in quantum technologies.

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Figure 1: A quantum dot with a light-hole exciton ground state.
Figure 2: Representative micro-photoluminescence spectra of heavy-hole and light-hole excitons in single GaAs/AlGaAs quantum dots.
Figure 3: Representative polarization-resolved micro-photoluminescence spectra of light-hole excitons in a magnetic field applied along the growth direction (Faraday configuration).
Figure 4: Calculation results using the experimental quantum-dot structure.
Figure 5: Strain tuning of a light-hole exciton.

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Acknowledgements

We acknowledge P. Atkinson, Ch. Deneke, D. J. Thurmer and R. Engelhard for assistance with the molecular beam epitaxy, D. Grimm, B. Martin and S. Harazim for assistance in clean room maintenance, and G. Katsaros and R. Rezaev for fruitful discussions. This work was financially supported by the BMBF project QuaHL-Rep (Contracts no. 01BQ1032 and 01BQ1034), the DFG FOR730, the FOM (VIDI Grant), the European Union Seventh Framework Programme 209 (FP7/2007-2013) under Grant Agreement No. 601126 210 (HANAS) and the ERANET project QOptInt.

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Contributions

Y.H.H. grew and processed samples, measured micro-photoluminescence, and analysed data supported by S.K., J.X.Z., E.Z., R.T. and F.D., under supervision of A.R. and O.G.S. B.J.W. carried out micro-photoluminescence in magnetic field supported by N.A. and V.Z. and provided insightful interpretation of the experimental and theoretical results. J.R.C., R.S. and G.B. performed pseudopotential calculations and developed the mesoscopic model. R.G., D.K. and J.S. performed X-ray diffraction measurements. All authors discussed the results and contributed to the manuscript. A.R. conceived and coordinated the project, triggered by V.Z. and N.A.

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Correspondence to Y. H. Huo or B. J. Witek or G. Bester or A. Rastelli.

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The authors declare no competing financial interests.

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Huo, Y., Witek, B., Kumar, S. et al. A light-hole exciton in a quantum dot. Nature Phys 10, 46–51 (2014). https://doi.org/10.1038/nphys2799

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