arXiv subjects

V. Voliotis

Publications and source records attributed to V. Voliotis.

7 recordsLinked to original sources

arXiv2025

Probing moire excitons in MoSe2/WSe2 heterobilayers by combined micro-photoluminescence and lateral force microscopy

We study interlayer excitons in MoSe2/WSe2 heterobilayers, by combining lateral force microscopy and micro-photoluminescence spectroscopy. This allows us to correlate the spatial profile of the moir\'e superlattice with the distribution of optically active states accessible to interlayer excitons. In heterostructures where a few degrees twist angle is imposed between the MoSe and WSe crystallographic axes, we show that a continuous moir\'e lattice is realized across areas close to the optical diffraction limit. In such regions, the photoluminescence reduces to a few narrow-band lines only, energetically distributed consistently with the geometry of the moir\'e lattice. This correlation reveals that interlayer excitons explore a controlled periodic confinement, paving the way towards implementations of Bose-Hubbard models.

cond-mat.mes-hall↗

arXiv2013

Influence of exciton spin relaxation on the photoluminescence spectra of semimagnetic quantum dots

We present a comprehensive experimental and theoretical studies of photoluminescence of single CdMnTe quantum dots with Mn content x ranging from 0.01 to 0.2. We distinguish three stages of the equilibration of the exciton-Mn ion spin system and show that the intermediate stage, in which the exciton spin is relaxed, while the total equilibrium is not attained, gives rise to a specific asymmetric shape of the photoluminescence spectrum. From an excellent agreement between the measured and calculated spectra we are able to evaluate the exciton localization volume, number of paramagnetic Mn ions, and their temperature for each particular dot. We discuss the values of these parameters and compare them with results of other experiments. Furthermore, we analyze the dependence of average Zeeman shifts and transition linewidths on the Mn content and point out specific processes, which control these values at particular Mn concentrations.

cond-mat.mes-hall↗

arXiv2011

Polarization properties of excitonic qu-bits in single self-assembled quantum dots

We investigate polarization properties of neutral exciton emission in single self-assembled InAs/GaAs quantum dots. The in-plane shape and strain anisotropy strongly couple the heavy and light hole states and lead to large optical anisotropy with non-orthogonal linearly polarized states misaligned with respect to the crystallographic axes. Owing to a waveguiding experimental configuration, luminescence polarization along the growth axis has been observed revealing the presence of shear components of the deformation tensor out of the growth plane. Resonant luminescence experiments allowed determining the oscillator strength ratio of the two exciton eigenstates. Valence band mixing governs this ratio and can be very different from dot to dot, however the polarization anisotropy axis is quite fixed inside a scanned area of one \mum^{2} and indicates that the in-plane deformation direction to which it is related has a correlation length of the order of magnitude of one \mum^{2}.

cond-mat.mes-hall↗

arXiv2007

Resonant excitonic emission of a single quantum dot in the Rabi regime

We report on coherent resonant emission of the fundamental exciton state in a single semiconductor GaAs quantum dot. Resonant regime with picoseconde laser excitation is realized by embedding the quantum dots in a waveguiding structure. As the pulse intensity is increased, Rabi oscillation is observed up to three periods. The Rabi regime is achieved owing to an enhanced light-matter coupling in the waveguide. This is due to a \emph{slow light effect} ($c/v_{g}\simeq 3000$), occuring when an intense resonant pulse propagates in a medium. The resonant control of the quantum dot fundamental transition opens new possibilities in quantum state manipulation and quantum optics experiments in condensed matter physics.

cond-mat.mes-hall↗

arXiv2006

Electron teleportation between quantum dots using virtual dark exciton

We here propose a mechanism to teleport electrons between quantum dots through the transformation of a virtual bright exciton into a dark exciton. This mechanism relies on the interactions of two composite bosons: a pair of electrons with opposite spins, trapped in two dots and an electron-hole pair in a free exciton coupled to an unabsorbed pump pulse, which makes it ``bright'' but virtual. This bright exciton first turns ``dark'' by dropping its electron and stealing the trapped electron with opposite spin through an exchange Coulomb process with the trapped pair. In a second step, the dark exciton ``flies'' with its electron to the other dot where it turns bright again, by the inverse process. The ``Shiva diagrams'' for composite boson many-body effects that we have recently introduced, enlighten this understanding.

cond-mat.mes-hall↗

arXiv2005

Macroscopic coherence of a single exciton state in a polydiacetylene organic quantum wire

We show that a single exciton state in an individual ordered conjugated polymer chain exhibits macroscopic quantum spatial coherence reaching tens of microns, limited by the chain length. The spatial coherence of the k=0 exciton state is demonstrated by selecting two spatially separated emitting regions of the chain and observing their interference.

cond-mat.str-el↗

arXiv2005

Evidence of polariton induced transparency in a single organic quantum wire

The resonant interaction between quasi-one dimensional excitons and photons is investigated. For a single isolated organic quantum wire, embedded in its single crystal monomer matrix, the strong exciton-photon coupling regime is reached. This is evidenced by the suppression of the resonant excitonic absorption arising when the system eigenstate is a polariton. These observations demonstrate that the resonant excitonic absorption in a semiconductor can be understood in terms of a balance between the exciton coherence time and the Rabi period between exciton-like and photon-like states of the polariton.

cond-mat.str-el↗