L. Besombes's research while affiliated with Institut Néel and other places
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Publications (123)
Two electrons in a quantum dot (QD) can form triplet states. We analyze the exchange coupling of the triplet states of the negatively charged exciton in a QD (X−, two electrons and one hole) with the spin of a magnetic atom (Mn). Two techniques are used to access the spin structure of this magnetic complex: the resonant excitation of the excited st...
Two electrons in a quantum dot (QD) can form triplet states. We analyze the exchange coupling of the triplet states of the negatively charged exciton in a QD (X$^-$, two electrons and one hole) with the spin of a magnetic atom (Mn). Two techniques are used to access the spin structure of this magnetic complex: the resonant excitation of the excited...
We study the dynamics of the spin system that consists of a positively charged II-VI semiconductor quantum dot doped with a single Cr+ ion. The resonant photoluminescence (PL) of the positively charged exciton coupled with the Cr+ spin is used to analyze the main spin relaxation channels. The intensity of the resonant PL is reduced by an optical pu...
We study the dynamics of the spin system that consist of a positively charged II-VI semiconductor quantum dot doped with a single Cr$^+$ ion. The resonant photoluminescence (PL) of the positively charged exciton coupled with the Cr$^+$ spin is used to analyze the main spin relaxation channels. The intensity of the resonant PL is reduced by an optic...
We study a diluted magnetic semiconductor system based on the spin of the ionized acceptor Cr+. We show that the negatively charged Cr+ ion, an excited state of the Cr in II-VI semiconductor, can be stable when inserted in a CdTe quantum dot (QD). The Cr+ attracts a heavy hole in the QD and form a stable hole-Cr+ complex. Optical probing of this sy...
We study a new diluted magnetic semiconductor system based on the spin of the ionized acceptor Cr$^+$. We show that the negatively charged Cr$^+$ ion, an excited state of the Cr in II-VI semiconductor, can be stable when inserted in a CdTe quantum dot (QD). The Cr$^+$ attracts a heavy-hole in the QD and form a stable hole-Cr$^+$ complex. Optical pr...
Polariton photoluminescence from cylindrical microcavities was studied under optical excitation below and above a nonlinear regime threshold. Lines of lateral excitonic polaritons quantization were observed in the spectra. In addition to quantization lines with a small orbital quantum number m, exciton-polariton whispering gallery modes with large...
The spectra of exciton-polariton photoluminescence from cylindrical microcavities under optical excitation below and above the threshold of transition to the polariton laser regime under conditions of strong exciton-photon coupling were studied. At relatively weak optical excitation, lateral quantization modes of polaritons and whispering gallery m...
We demonstrate radio-frequency tuning of the energy of individual CdTe/ZnTe quantum dots (QDs) by Surface Acoustic Waves (SAWs). Despite the very weak piezoelectric coefficient of ZnTe, SAW in the GHz range can be launched on a ZnTe surface using interdigitated transducers deposited on a c-axis oriented ZnO layer grown on ZnTe containing CdTe QDs....
We demonstrate radio-frequency tuning of the energy of individual CdTe/ZnTe quantum dots (QDs) by Surface Acoustic Waves (SAWs). Despite the very weak piezoelectric coefficient of ZnTe, SAW in the GHz range can be launched on a ZnTe surface using interdigitated transducers deposited on a c-axis oriented ZnO layer grown on ZnTe containing CdTe QDs....
We analyze the influence of optically generated nonequilibrium phonons on the spin relaxation and effective spin temperature of an individual Cr atom inserted in a quantum dot. Using a three-pulse pump-probe technique, we show that the spin relaxation measured in resonant optical pumping experiments strongly depends on the optical excitation condit...
We study the emission of individual quantum dots in CdTe/ZnTe samples doped with a low concentration of Cr. In addition to dots with a photoluminescence (PL) split by the exchange interaction with a magnetic Cr atom, we observe another type of dots with a complex PL structure composed of a minimum of six lines on the exciton and biexciton and three...
We analyse the influence of optically generated non-equilibrium phonons on the spin relaxation and effective spin temperature of an individual Cr atom inserted in a quantum dot. Using a three pulses pump-probe technique, we show that the spin relaxation measured in resonant optical pumping experiments strongly depends on the optical excitation cond...
We demonstrate that the spin of a Cr atom in a quantum dot (QD) can be controlled optically and we discuss the main properties of this single spin system. The photoluminescence of individual Cr-doped QDs and their evolution in magnetic field reveal a large magnetic anisotropy of the Cr spin induced by local strain. This results in a splitting of th...
The dependences of the exciton-polariton photoluminescence spectra on the intensity of optical excitation and external magnetic fields are investigated in cylindrical mesas based on high-quality microcavities. It was found that with an increase of the intensity of optical excitation above a certain threshold at sufficiently large magnetic field or...
We study the emission of individual quantum dots in CdTe/ZnTe samples doped with a low concentration of Cr. In addition to dots with a photoluminescence (PL) split by the exchange interaction with a magnetic Cr atom, we observe another type of dots with a complex PL structure composed of a minimum of six lines on the exciton and biexciton and three...
Photoluminescence spectra of an isolated GaAs quantum dot within an AlGaAs quantum wire are studied. The examination of behavior of spectra in a magnetic field provided an opportunity to estimate the exciton binding energy in the quantum dot, which turned out to be 10 times higher than the bulk exciton binding energy in GaAs. It is demonstrated tha...
A detailed analysis of the photoluminescence (PL) intensity distribution in singly Cr-doped CdTe/ZnTe quantum dots (QDs) is performed. First of all, we demonstrate that hole-Cr flip-flops induced by an interplay of the hole-Cr exchange interaction and the coupling with acoustic phonons are the main source of spin relaxation within the exciton-Cr co...
Photoluminescence spectra of an isolated GaAs quantum dot within an AlGaAs quantum wire are studied. The examination of behavior of spectra in a magnetic field provided an opportunity to estimate the exciton binding energy in the quantum dot, which turned out to be 10 times higher than the bulk exciton binding energy in GaAs. It is demonstrated tha...
We analyze, through resonant photoluminescence, the spin dynamics of an individual magnetic atom (Mn) coupled to a hole in a semiconductor quantum dot. The hybrid Mn-hole spin and the positively charged exciton in a CdTe/ZnTe quantum dot forms an ensemble of $\Lambda$ systems which can be addressed optically. Auto-correlation of the resonant photol...
The photoluminescence spectra of individual quantum dots incorporated into a quantum wire are studied. From the behavior of the spectra in a magnetic field, it is possible to estimate the exciton binding energy in a quantum dot incorporated into a quantum wire. It is found that the exciton photoluminescence signal emitted from a quantum dot along t...
The photoluminescence spectra of exciton polaritons in microcavities under conditions of three-dimensional quantization are studied as a factor of the density of the optical excitation and magnetic field. The behavior of the degree of circular polarization of the exciton luminescence in a magnetic field shows that, when the concentration of exciton...
A Cr atom in a semiconductor host carries a localized spin with an intrinsic large spin to strain coupling particularly promising for the development of hybrid spin-mechanical systems and coherent mechanical spin driving. We demonstrate here that the spin of an individual Cr atom inserted in a semiconductor quantum dot can be controlled optically....
We studied the spin dynamics of a Cr atom incorporated in a II-VI semiconductor quantum dot using photon correlation techniques. We used recently developed singly Cr-doped CdTe/ZnTe quantum dots (A. Lafuente-Sampietro {\it et al.}, [1]) to access the spin of an individual magnetic atom. Auto-correlation of the photons emitted by the quantum dot und...
We demonstrate the optical addressability of the spin of an individual chromium atom (Cr) embedded in a semiconductor quantum dot. The emission of Cr-doped quantum dots and their evolution in magnetic field reveal a large magnetic anisotropy of the Cr spin induced by local strain. This results in the zero field splitting of the 0, ±1, and ±2 Cr spi...
We probe the spin dynamics of an individual magnetic atom (Mn) coupled to carriers in a positively charged quantum dot using resonant photoluminescence. We demonstrate that a p-doped CdTe/ZnTe quantum dot containing a single Mn atom forms an ensemble of optical Λ systems which can be addressed independently. Performing resonant optical pumping expe...
Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also...
Исследованы спектры фотолюминесценции экситонных поляритонов в микрорезонаторах в условиях 3-мерного квантования в зависимости от плотности оптического возбуждения и магнитного поля. По поведению степени круговой поляризации экситонной люминесценции в магнитном поле установлено, что при повышении концентрации экситонов они конденсируются на самом н...
-1 Исследовались спектры фотолюминесценции одиночных квантовых точек, заключенных в квантовую нить. Из поведения спектров в магнитном поле удалось оценить энергию связи экситона в квантовой точке, заключенной в квантовую нить. Обнаружено, что сигнал экситонной фотолюминесценции из квантовой точки, излучаемый в направлении оси нанонити, поляризован...
We report on the coherent dynamics of the spin of an individual magnetic atom
coupled to carriers in a semiconductor quantum dot which has been investigated
by resonant photoluminescence of the positively charged exciton (X+). We
demonstrate that a positively charged CdTe/ZnTe quantum dot doped with a single
Mn atom forms an ensemble of optical Lam...
The control of single spins in solids is a key but challenging step for any
spin-based solid-state quantumcomputing device. Thanks to their expected long
coherence time, localized spins on magnetic atoms in a semiconductor host could
be an interesting media to store quantum information in the solid state. Optical
probing and control of the spin of...
Using the emission of the positively charged exciton as a probe, we analyze
the dynamics of the optical pumping and the dynamics of the relaxation of a Mn
spin exchange-coupled with a confined hole spin in a II-VI semiconductor
quantum dot. The hole-Mn spin can be efficiently initialized in a few tens of
$ns$ under optical injection of spin polariz...
In this paper we predicted and observed a new magneto-optical effect – the “effect of parity”. The effect is manifest as a redistribution of the oscillator strengths between spatially even and odd center of mass quantized states of the exciton in the quantum well. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
We report on a study of the photoluminescence spectra taken from quasi one-dimensional and quasi zero-dimensional semiconductor heterostructures. The structures were grown by molecular-beam epitaxy in (111) direction and were cylindrical nanowires based on AlGaAs, of 20 - 50 nm in diameter and 0.5 - 1 μm in length. Inside the nanowires contain one...
We report on the spin properties of individual Mn atoms in II-VI
semiconductor strain free quantum dots. Strain free Mn-doped CdTe quantum dots
are formed by width fluctuations in thin quantum wells lattice matched on a
CdTe substrate. These quantum dots permit to optically probe and address any
spin state of a Mn atom in a controlled strain enviro...
The magnetic field effect on phase transitions in electrically neutral
bosonic systems is much less studied than those in fermionic systems, such as
superconducting or ferromagnetic phase transitions. Nevertheless, composite
bosons are strongly sensitive to magnetic fields: both their internal structure
and motion as whole particles may be affected...
We report on a numerical model of quasi-1-D and quasi-0-dimensional semiconductor heterostructures. This model is strictly based on experimental structures of cylindrical nanocolumns of AlGaAs grown by molecular-beam epitaxy in the (1 1 1) direction. The nanocolumns are of 20-50 nm in diameter and 0.5-1 μm in length and contain a single GaAs quantu...
We report on a numerical model of quasi-1-D and quasi-0-dimensional semiconductor heterostructures. This model is strictly based on experimental structures of cylindrical nanocolumns of AlGaAs grown by molecular-beam epitaxy in the (1 1 1) direction. The nanocolumns are of 20-50 nm in diameter and 0.5-1 μm in length and contain a single GaAs quantu...
We present a numerical model of quasi one-dimensional and quasi zero-dimensional semiconductor heterostructures strictly based on experimental structures of polyphorm cylindrical nanocolumns.
The photoluminescence (PL) spectra of semiconductor structures, namely, Al0.3Ga0.7As-based quasi-one-dimensional cylindrical nanowires (nanowhiskers), are measured. The diameter of a typical nanowire is 20–50 nm, and its length was 0.5–1.0 μm. Samples containing one or several GaAs-based quantum dots at the center of the quantum wire are studied. T...
We observe a systematic red shift of the band-edge of passivated
GaAs/Al0.35Ga0.65As core-shell nanowires with increasing shell thickness up to
100 nm. The shift is detected both in emission and absorption experiments,
reaching values up to 14 meV for the thickest shell nanowires. Part of this red
shift is accounted for by the small tensile strain...
We analyze the spin dynamics of an individual magnetic atom (Mn) inserted in
a II-VI semiconductor quantum dot under resonant optical excitation. In
addition to standard optical pumping expected for a resonant excitation, we
show that for particular conditions of laser detuning and excitation intensity,
the spin population can be trapped in the sta...
This manuscript is organized as follows: In Part One, the main properties of Mn-doped and singly charged II-VI QDs are presented. In chapter 1 we will describe their energy level structure. We will then analyze in detail the influence of the QD symmetry and of the valence band mixing on the spin structure of QDs containing an individual carrier and...
The reflection and photoluminescence spectra of modulation-doped CdTe/CdMgTe quantum-well structures have been studied. It was found that the magnitude and sign of the Zeeman splitting of the trion reflection line depend on the electron concentration in the quantum well, whereas the magnitude and sign of the splitting of the exciton line are absolu...
The results of a study into the photoluminescence spectra of a set of quantum dots based on GaAs enclosed in AlGaAs nanowires are presented. The steady state and time resolved spectra of photoluminescence under optical excitation both from an array of quantum wires/dots and a single quantum wire/dot have been measured. In the photoluminescence spec...
We show in this review that the spin state of a single magnetic atom embedded in an individual semiconductor quantum dot can be optically probed. A high degree of spin polarization can be achieved for an individual Mn atom using quasi-resonant or fully resonant optical excitation of the quantum dot at zero magnetic field. Under quasi-resonant excit...
Spectral diffusion is a result of random spectral jumps of a narrow line as a
result of a fluctuating environment. It is an important issue in spectroscopy,
because the observed spectral broadening prevents access to the intrinsic line
properties. However, its characteristic parameters provide local information on
the environment of a light emitter...
We report on the optical spectroscopy of the spin of two magnetic atoms (Mn)
embedded in an individual quantum dot interacting with either a single
electron, a single exciton and single trion. As a result of their interaction
to a common entity, the Mn spins become correlated. The dynamics of this
process is probed by time resolved spectroscopy, th...
We report on the dynamics of optically induced nuclear spin polarization in
individual CdTe/ZnTe quantum dots loaded with one electron by modulation
doping. The fine structure of the hot trion (charged exciton $X^-$ with an
electron in the $P$-shell) is identified in photoluminescence excitation
spectra. A negative polarisation rate of the photolum...
We have investigated the spin preparation efficiency by optical pumping
of single Mn atoms embedded in CdTe/ZnTe quantum dots. Monitoring the
time dependence of the intensity of the resonant fluorescence during the
optical pumping process allows direct probing of the efficiency of the
Mn spin initialization, providing preparation and read-out in th...
A fast Tellurium induced formation of CdTe/ZnTe quantum dots (QDs) has
been investigated. A systematic approach, based on Reflection High
Energy Electron Diffraction (RHEED), has been followed to determine the
Te deposition parameters that drives the 2D-3D transition in a 10 times
shorter time than the reported technique based on the deposition of...
We present a systematic study of the CdTe/ZnTe quantum dots (QDs) formation induced by tellurium (Te) deposition and desorption. The investigation of the QDs formation was performed by reflection high electron energy diffraction analysis as a function of the Te deposition time and temperature. We show that the Te can be deposited at a temperature a...
Exciton luminescence of a CdSe quantum dot (QD) inserted in a ZnSe nanowire
is strongly influenced by the dark exciton states. Because of the small size of
these QDs (2-5nm), exchange interaction between hole and electron is highly
enhanced and we measured large energy splitting between bright and dark exciton
states ($\Delta E\in [4, 9.2 ]$ meV) a...
We report on the observation of spin-dependent optically dressed states and the optical Stark effect on an individual Mn spin in a semiconductor quantum dot. The vacuum-to-exciton or the exciton-to-biexciton transitions in a Mn-doped quantum dot are optically dressed by a strong laser field, and the resulting spectral signature is measured in photo...
The spin dynamics of a single Mn atom in a laser driven CdTe quantum dot is
addressed theoretically. Recent experimental
results\cite{Le-Gall_PRL_2009,Goryca_PRL_2009,Le-Gall_PRB_2010}show that it is
possible to induce Mn spin polarization by means of circularly polarized
optical pumping. Pumping is made possible by the faster Mn spin relaxation in...
The effects of charge-density fluctuations on negative trion states in a quantum well are considered for the case of intermediate doping by electrons at zero magnetic field. The quasi-two-dimensionality of the system and the trion-plasmon interaction are taken into account in the framework of the random-phase approximation. It is shown that the tri...
We have studied spectral diffusion of the photoluminescence of a single CdSe
quantum dot inserted in a ZnSe nanowire. We have measured the characteristic
diffusion time as a function of pumping power and temperature using a recently
developed technique [G. Sallen et al, Nature Photon. \textbf{4}, 696 (2010)]
that offers subnanosecond resolution. Th...
Exciton-polariton reflectivity of wide CdTe/CdZnTe quantum-wells (with well widths exceeding by far the exciton Bohr radius) was measured in the Voigt geometry in a magnetic field. In a magnetic field, forbidden exciton lines were observed to appear for each exciton quantization level. The exciton diamagnetic shift constant was observed to decrease...
Reflectivity and photoluminescence spectra from CdTe/CdMgTe modulation-doped quantum well structures were studied. We have found that in reflectivity spectra the value and the sign of the Zeeman splitting of the trion lines depend on the electron concentration in the quantum well, whereas, the value and sign of the exciton line splitting are consta...
Reflectivity and photoluminescence spectra from CdTe/CdMgTe modulation doped quantum well structures were studied. We have found that the value and the sign of the trion reflectivity line's Zeeman splitting depends on the electron concentration in the quantum well, whereas the value and sign of the exciton line splitting are absolutely equal for al...
For low Mn-doped Cd(Mn)Te/ZnTe single quantum dots, we report a
nonlinear behavior of exciton energy as a function of magnetic field,
which differs from the usual giant Zeeman effect. This effect is modeled
by a positive feedback loop in the heating process of Mn spins by
carriers photocreated in the vicinity of the dot. It results in a highly
nonl...
We demonstrate a high degree of an optical spin preparation of a single Mn atom embedded in a CdTe/ZnTe quantum dot (QD). Due to the strong exchange interaction of the manganese atom with an exciton injected into the QD the spin orientation can be achieved by quasi-resonant or fully-resonant optical creation of the polarized electron-hole pairs. A...
We present a model for the incoherent spin dynamics of a Mn atom inside a CdTe quantum dot resonantly pumped by a laser light. The relevant quantum states of the system, 2S + 1 = 6 spin states in the optical ground state and the 24 = (2S + 1) * (2Se + 1) * (2Sh + 1) are obtained from a effective spin Hamiltonian which describes the basic features o...
We have investigated the spin preparation efficiency by optical pumping of
individual Mn atoms embedded in CdTe/ZnTe quantum dots. Monitoring the time
dependence of the intensity of the fluorescence during the resonant optical
pumping process in individual quantum dots allows to directly probe the
dynamics of the initialization of the Mn spin. This...
We describe selected results obtained on diluted magnetic semiconductors, from the growth by molecular beam epitaxy to the study of the magnetic, magneto-optical and magneto-transport prop-erties associated to carrier induced ferromagnetism in layers, quantum wells, nanocolumns, and to the coherent manipulation of a single Mn spin in a quantum dot....
Special growth conditions are presented in this work, in order to produce ZnTe/ZnSe type-II quantum dots and preserve them during the capping stage. A detailed study emphasizes the high sensitivity of the sample structure to Se/Zn ratio as opposed to other growth parameters. It is shown that nominally identical samples can evolve into two-dimension...
An optical spin orientation is achieved for a Mn atom localized in a semiconductor quantum dot using quasiresonant excitation at zero magnetic field. Optically created spin polarized carriers generate an energy splitting of the Mn spin and enable magnetic moment orientation controlled by the photon helicity and energy.
The dynamics and the magnetic...
We have carried out a detailed optical characterization of a single CdSe quantum dot embedded in a ZnSe nanowire. Exciton, biexciton, and charged exciton lines have been identified unambiguously using photon correlation spectroscopy. This technique has provided a detailed picture of the dynamics of this system. It has been found that the dark excit...
ZnTe/ZnSe type-II heterostructures interfaces were investigated versus growth conditions. A well controlled Se/Zn flux ratio allows us to control the structures type: quantum dots with excitonic recombination of around 5 ns photoluminescence decay time or a quantum well with spatially indirect recombination with a much longer decay close to 100 ns....
We analyzed the photoluminescence intermittency generated by a single
paramagnetic spin localized in an individual semiconductor quantum dot.
The statistics of the photons emitted by the quantum dot reflect the
quantum fluctuations of the localized spin interacting with the injected
carriers. Photon correlation measurements which are reported here...
We present the photoluminescence and time resolved photoluminescence properties of an ensemble of ZnTe quantum dots embedded in a ZnSe matrix. Those heterostructures exhibit a type-II band alignment with holes confined within the dots and electrons kept in the close vicinity of the dots by coulomb attraction. We show that the structural and optical...
An optical spin orientation is achieved for a Mn atom localized in a semiconductor quantum dot using quasiresonant excitation at zero magnetic field. Optically created spin-polarized carriers generate an energy splitting of the Mn spin and enable magnetic moment orientation controlled by the photon helicity and energy. The dynamics and the magnetic...
Magneto optical micro-spectroscopy allowed us to access the magnetic field dependency of the photoluminescence of Cd(Mn)Te/ZnTe single quantum dots. We report a strongly non-linear behavior of the exciton and biexciton energies as a function of magnetic field which clearly differs from the expected and usually observed giant Zeeman effect. We demon...
Photoluminescence of a single CdSe quantum dot embedded in a ZnSe nanowire has been investigated. It has been found that the dark exciton has a strong influence on the optical properties. The most visible influence is the strongly reduced excitonic emission compared to the biexcitonic one. Temperature dependent lifetime measurements have allowed us...
This chapter discusses the quantum structures of II–VI diluted magnetic semiconductors (DMSs) and some advantages of an important fact concerning the II–VI DMSs that Mn substitutes the column-II cations as an isoelectronic impurity, as opposed to the acceptor character observed in III–V ones. Carrier-induced ferromagnetism in (Cd,Mn)Te QWs constitu...
This chapter reviews that when magneto-electronic devices scales down, it becomes increasingly important to understand the properties of a single magnetic atom in a solid-state environment. Atomic scale surface probes are successfully used in this regard. More recently, optical probing of both magnetic and non-magnetic atoms in semiconductors is de...
The magnetic state of a single magnetic ion (Mn2+) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn2+ ion (S = 5 / 2) is analyzed in detail. The exciton-Mn2+ exchange interaction shifts the energy of the exciton depending on the Mn2+ spin...
We analyzed the photoluminescence intermittency generated by a single paramagnetic spin localized in an individual semiconductor quantum dot. The statistics of the photons emitted by the quantum dot reflect the quantum fluctuations of the localized spin interacting with the injected carriers. Photon correlation measurements, which are reported here...
We report time-resolved photoluminescence experiments in p-doped single CdTe/ZnTe quantum dots (QDs) with a number of resident holes ranging from 0 to 2. Under resonant circularly polarized excitation on an excited state, the charged species present a large polarization rate at a short time delay. A significant reduction of this initial polarizatio...
We have performed a detailed study of the growth conditions of ZnTe strained on ZnSe to form nanometer-scale islands. We determined that the critical thickness for strain relaxation was 2 ML, rapidly followed by the onset of surface undulations due to a layer instability. Nevertheless, the changes in the surface morphology were not marked enough if...
Photoluminescence spectra of strained structures Zn1 − x
Mn
x
Te/Zn1 − y
Mg
y
Te with magnetic quantum wells and nonmagnetic barriers are studied. The Zeeman splitting of the heavy exciton is found to
follow an unusual behavior: both spin components shift down in energy. The heavy-exciton photoluminescence Zeeman components
are observed to be inver...
The phenomenon in which giant enhancement of exciton magnetic moments occurs due to translational motion was found for light hole excitons in ZnTe/ZnMgTe quantum well structures. Decreasing diamagnetic shifts as the number of the exciton quantized state increases were found for the first time.
We analyze the optical emission of single II-VI quantum dots containing 0 or 1 magnetic atom (manganese) and a controlled number of carriers (0, ±1 electron). The emission of these quantum dots presents a large degree of linear polarization. This linear polarization is attributed to a valence-band mixing and we show that in nonmagnetic quantum dots...
The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier are analyzed. The emission of the neutral, negatively and positively charged excitons coupled with a single magnetic atom (Mn) are observed in the same individual quantum dot. The spectrum of the charged excitons in interaction with the M...
Method of growth to get one single Mn in self‐assembled semiconductors
Quantum Dot
(QD) is presented. A simple model proves that a very low Mn density is needed prior to the QD
nucleation. This was reached by inserting a thin ZnTe spacer between a Zn
1−x
Mn
x
Te buffer and the CdTe
QD layer. Control of Mn ions density is made by changing the th...
We analyze the optical emission of neutral, positively and negatively charged excitons in single II-VI quantum dots presenting a high degree of linear polarization. This linear polarization is attributed to a valence band mixing and we show that in QDs combining both a shape anisotropy and an anisotropic in-plane strain distribution, the linear pol...
The magnetic state of a single magnetic ion (Mn2+) embedded in an individual quantum dot is optically probed using micro-spectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn2+ ion (S=) is analyzed in detail. The exciton–Mn2+ exchange interaction shifts the energy of the exciton depending on the Mn2+ spin compo...
The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier (electron or hole) are analyzed. The emission of the neutral, positively charged and negatively charged excitons coupled with a single magnetic atom are observed in the same quantum dot. The spectrum of the charged excitons in interaction...
The fine structure of excited excitonic states in a quantum dot with an embedded magnetic ion is studied theoretically and experimentally. The developed theory takes into account the Coulomb interaction between charged carriers, the anisotropic long-range electron-hole exchange interaction in the zero-dimensional exciton, and the exchange interacti...
A method of growth to get one single Mn in self-assembled semiconductor quantum dot is presented. With a simple quantitative model, the appropriate low Mn density needed prior to the quantum dot nucleation is estimated. Such a low Mn concentration was reached by inserting a thin ZnTe spacer between a Zn1−xMnxTe buffer and the CdTe quantum dot layer...
The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier (electron or hole) are analyzed. Bias controlled single-carrier charging combined with photo depletion is used to control the charge state of individual Mn-doped quantum dots. The emission of the neutral, negatively charged and positively...
We report on the reversible electrical control of the magnetic properties of a single Mn atom in an individual quantum dot. Our device permits us to prepare the dot in states with three different electric charges, 0, +1e, and -1e which result in dramatically different spin properties, as revealed by photoluminescence. Whereas in the neutral configu...
The optical studies of negative trions in CdSe quantum dots under magnetic field in Voigt geometry reveal large hole g -factors, reaching values as high as the value of electron g -factors. This observation is attributed to strong mixing of heavy hole and light hole states induced by an in-plane asymmetric shape of the quantum dots. The large hole...
The anisotropy in the exchange interaction between a single magnetic
atom and a single exciton confined in a quantum dot (QD) is revealed
experimentally. In a transverse magnetic field we directly observe the
orientation of the magnetic ion spin along the resultant direction of
the external magnetic field and the hole exchange field. With an
increa...
Citations
... Isolated spatially-localized spins in semiconducting or insulating materials are promising quantum states for implementing information storage and processing technologies [1,2]. While current ultimate memory elements are still made of a huge number of spins or charges, the reducing of this number toward unity or so has now became a reachable goal [3][4][5], leading to solotronic devices [6]. Besides, solid-state quantum computing and quantum metrology are also demanding for localized spin-systems, embedded in solid and robust insulating crystalline matrix [7,8]. ...
... Besides, strain is used to modulate the quantum integrated photonics, cavities, and spin properties as well [10][11][12]. Acoustic wave generated by piezoelectric materials could also apply strain to photon emitters that adheres to the surface [13]. A range of approaches to manipulate the state of quantum light have been demonstrated. ...
... It has been demonstrated that the spin states S z = ±1 of a Cr atom in CdTe can be prepared and readout optically and present a relaxation time larger than 10 µs at low temperature 22 . In analogy with the spin structure of NV centers in diamond, the spin states S z = ±1 of Cr in a selfassembled QD form a qubit ({+1; −1} spin qubit) strongly coupled to in-plane strain 14 . ...
... Bussian et al [57] showed the Zeeman energy splitting could be tuned from about −14 meV to +7 meV by increasing the thickness of a CdSe shell surrounding a Mn 2+ -doped ZnSe core, which localises the hole in the shell away from dopant and so reduces ∆E h relative to ∆E e . Significant exchange interactions have also been demonstrated for other TM dopants, such as Cu 2+ [58], Co 2+ [59] and Cr 2+ [60]. ...
![[object Object]](https://i1.rgstatic.net/ii/profile.image/381165673435138-1467888386591_Q64/Lafuente-Sampietro-Alban.jpg)
... As we show, the simple picture is invalidated by the interplay between optical orientation of the exciton and the non-trivial dependence of the TM ion spin on the selection rules in anisotropic quantum dots. Our considerations will be showcased using a particular system of a CdSe/ZnSe QD with single Fe 2+ ion [14], but the same reasoning should be valid also for all other known systems of that kind [20][21][22]. ...
... To measure the dark-bright exciton coupling [33,34], a longitudinal magnetic field was applied to QD#A. The experimental conditions are the same as those used in Fig. 4(a). ...
... [7][8][9]. Our findings could be especially useful in all studies involving spin-related phenomena in CdTe-based MBE-grown nanostructures and devices including multiple-QWs and quantum dots [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28]. 2. (a) A schematic of a representative sample structure used in the whole sample series used in this article. ...
... Например, поле одноосного сжатия, приложенное к широкой КЯ, индуцирует эффект сближения масс экситонов тяжелой и легкой дырок и приводит к инверсии фазы спектральных осцилляций экситонных особенностей в оптических спектрах [14,15]. Магнитное поле, в зависимости от ориентации относительно оси квантования, приводит либо к эффективному увеличению массы экситона, либо к зависимости g-фактора экситона от волнового вектора его движения [16][17][18][19][20][21][22][23][24]. ...
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... Cavity exciton-polaritons [1] are quasiparticles exhibiting fascinating phenomena such as Bose-Einstein condensation [2,3] and superfluidity [4]. Recently, there is a growing interest in the magnetooptical properties of cavity exciton-polaritons and their condensates [5][6][7][8][9], e.g., magnetic field tuning of spin levels paves the way to investigate polariton bistability [10] and spin multistability [11]. In this context, II-VI based microcavities are of particular interest since they allow to combine the magnetooptical properties of excitons in diluted magnetic semiconductors with cavity polaritons [12][13][14][15][16][17][18] giving rise to semimagnetic cavity polaritons [19][20][21][22][23]. ...
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... 40 More recently, a controllable occupation transfer between bright and dark excitons in a QD-cavity system was suggested. 41 Our method facilitates QDs with a single magnetic dopant, which can be deterministically fabricated for several years, 42 with dopand atoms like Manganese (Mn), 43,44 Cromium, 45 Iron, 46 or Cobalt. 47 Interestingly, the spin state of the dopant can be changed via optical control. ...
