3 research outputs found
Spin Splitting Anisotropy in Single Diluted Magnetic Nanowire Heterostructures
We study the impact of the nanowire
shape anisotropy on the spin splitting of excitonic photoluminescence.
The experiments are performed on individual ZnMnTe/ZnMgTe core/shell
nanowires as well as on ZnTe/ZnMgTe core/shell nanowires containing
optically active magnetic CdMnTe insertions. When the magnetic field
is oriented parallel to the nanowire axis, the spin splitting is several
times larger than for the perpendicular field. We interpret this pronounced
anisotropy as an effect of mixing of valence band states arising from
the strain present in the core/shell geometry. This interpretation
is further supported by theoretical calculations which allow to reproduce
experimental results
Inhibition and Enhancement of the Spontaneous Emission of Quantum Dots in Micropillar Cavities with Radial-Distributed Bragg Reflectors
We present a micropillar cavity where nondesired radial emission is inhibited. The photonic confinement in such a structure is improved by implementation of an additional concentric radial-distributed Bragg reflector. Such a reflector increases the reflectivity in all directions perpendicular to the micropillar axis from a typical value of 15–31% to above 98%. An inhibition of the spontaneous emission of off-resonant excitonic states of quantum dots embedded in the microcavity is revealed by time-resolved experiments. It proves a decreased density of photonic states related to unwanted radial leakage of photons out of the micropillar. For on-resonance conditions, we find that the dot emission rate is increased, evidencing the Purcell enhancement of spontaneous emission. The proposed design can increase the efficiency of single-photon sources and bring to micropillar cavities the functionalities based on lengthened decay times
Electrical Switch to the Resonant Magneto-Phonon Effect in Graphene
We report a comprehensive study of
the tuning with electric fields
of the resonant magneto-exciton optical phonon coupling in gated graphene.
For magnetic fields around <i>B</i> ∼ 25 T that correspond
to the range of the fundamental magneto-phonon resonance, the electron–phonon
coupling can be switched on and off by tuning the position of the
Fermi level in order to Pauli block the two fundamental inter-Landau
level excitations. The effects of such a profound change in the electronic
excitation spectrum are traced through investigations of the optical
phonon response in polarization resolved magneto-Raman scattering
experiments. We report on the observation of a splitting of the phonon
feature with satellite peaks developing at particular values of the
Landau level filling factor on the low or on the high energy side
of the phonon, depending on the relative energy of the discrete electronic
excitation and of the optical phonon. Shifts of the phonon energy
as large as ±60 cm<sup>–1</sup> are observed close to
the resonance. The intraband electronic excitation, the cyclotron
resonance, is shown to play a relevant role in the observed spectral
evolution of the phonon response