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Subject: Experimental methods × WGL Institute: IFWD ×

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    Experimental methods of post-growth tuning of the excitonic fine structure splitting in semiconductor quantum dots
    (New York, NY [u.a.] : Springer, 2012) Plumhof, J.D.; Trotta, R.; Rastelli, A.; Schmidt, O.G.
    Deterministic sources of polarization entangled photon pairs on demand are considered as important building blocks for quantum communication technology. It has been demonstrated that semiconductor quantum dots (QDs), which exhibit a sufficiently small excitonic fine structure splitting (FSS) can be used as triggered, on-chip sources of polarization entangled photon pairs. As-grown QDs usually do not have the required values of the FSS, making the availability of post-growth tuning techniques highly desired. This article reviews the effect of different post-growth treatments and external fields on the FSS such as thermal annealing, magnetic fields, the optical Stark effect, electric fields, and anisotropic stress. As a consequence of the tuning of the FSS, for some tuning techniques a rotation of the polarization of the emitted light is observed. The joint modification of polarization orientation and FSS can be described by an anticrossing of the bright excitonic states.
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    Manifestations of impurity-induced s±⇒s++ transition: Multiband model for dynamical response functions
    (Bristol : IOP, 2013) Efremov, D.; Golubov, A.A.; Dolgov, O.V.
    We investigate the effects of disorder on the density of states, the single-particle response function and optical conductivity in multiband superconductors with s± symmetry of the order parameter, where s± → s++ transition may take place. In the vicinity of the transition, the superconductive gapless regime is realized. It manifests itself in anomalies in the above-mentioned properties. As a result, intrinsically phase-insensitive experimental methods such as angle-resolved photoemission spectroscopy, tunneling and terahertz spectroscopy may be used to reveal information about the underlying order parameter symmetry.