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Stable uudd \bar s pentaquarks in the constituent quark model
http://hdl.handle.net/2268/165827
Title: Stable uudd \bar s pentaquarks in the constituent quark model
<br/>
<br/>Author, coauthor: Stancu, Floarea; Riska, D. O.
<br/>
<br/>Abstract: The stability of strange pentaquarks uudd (s) over bar is studied in a constituent quark model based on a flavorspin hyperfine interaction between quarks. With this interaction model, which schematically represents the Goldstone boson exchange interaction between constituent quarks, the lowest lying strange pentaquark is a pshell state with positive parity. The flavorspin interaction lowers the energy of the lowest pshell state below that of the lowest sshell state, which has negative parity because of the negative parity of the strange antiquark. It is found that the strange pentaquark can be stable against strong decay provided that the strange antiquark interacts by a fairly strong spinspin interaction with u and d quarks. This interaction has a form that corresponds to, eta meson exchange. Its strength may be inferred from the pi(0) decay width of D*(s) mesons. (C) 2003 Elsevier B.V. All rights reserved.

Evolution of nuclear shells with the Skyrme density dependent interaction
http://hdl.handle.net/2268/165791
Title: Evolution of nuclear shells with the Skyrme density dependent interaction
<br/>
<br/>Author, coauthor: Brink, D. M.; Stancu, Floarea
<br/>
<br/>Abstract: We present the evolution of the shell structure of nuclei in HartreeFock calculations using Skyrme's densitydependent effective nucleonnucleon interaction. The role of the tensor part of the Skyrme interaction to the HartreeFock spinorbit splitting in spherical spin unsaturated nuclei is reanalyzed. The contribution of a finite range tensor force to the spinorbit splitting in closed shell nuclei is calculated. It is found that the exact matrix elements of a Gaussian and of a onepion exchange tensor potential could be written as a product Skyrme's short range expression times a suppression factor which is almost constant for closed shell nuclei with mass number A >= 48. The suppression factor is similar to 0.15 for the onepion exchange potential.

Coherent Backscattering in Fock Space: A Signature of Quantum ManyBody Interference in Interacting Bosonic Systems
http://hdl.handle.net/2268/165555
Title: Coherent Backscattering in Fock Space: A Signature of Quantum ManyBody Interference in Interacting Bosonic Systems
<br/>
<br/>Author, coauthor: Engl, Thomas; Dujardin, Julien; Argüelles, Arturo; Schlagheck, Peter; Richter, Klaus; Urbina, Juan Diego
<br/>
<br/>Abstract: We predict a generic signature of quantum interference in manybody bosonic systems resulting in a coherent enhancement of the average return probability in Fock space. This enhancement is robust with respect to variations of external parameters even though it represents a dynamical manifestation of the delicate superposition principle in Fock space. It is a genuine quantum manybody effect that lies beyond the reach of any meanfield approach. Using a semiclassical approach based on interfering paths in Fock space, we calculate the magnitude of the backscattering peak and its dependence on gauge fields that break timereversal invariance. We confirm our predictions by comparing them to exact quantum evolution probabilities in BoseHubbard models, and discuss their relevance in the context of manybody thermalization.

Dynamics of pentaquarks in constituent quark models: Recent developments
http://hdl.handle.net/2268/165522
Title: Dynamics of pentaquarks in constituent quark models: Recent developments
<br/>
<br/>Author, coauthor: Stancu, Floarea
<br/>
<br/>Abstract: Some recent developments in the study of light and heavy pentaquarks
are reviewed, mainly within constituent quark models.
Emphasis is made on results obtained in the flavorspin model
where a nearly ideal octetantidecuplet mixing is obtained.
The charmed antisextet is reviewed in the context of an SU(4)
classification.

Positive parity pentaquarks in a Goldstone boson exchange model
http://hdl.handle.net/2268/165426
Title: Positive parity pentaquarks in a Goldstone boson exchange model
<br/>
<br/>Author, coauthor: Stancu, Floarea
<br/>
<br/>Abstract: We study the stability of the pentaquarks $uudd\overline{Q}$,
$uuds\overline{Q}$ and $udss\overline{Q}$ ($Q = c$ or $b$) of positive parity
in a constituent quark model based on Goldstone boson exchange interaction
between quarks. The pentaquark parity is the antiquark parity times that of a
quark excited to a pshell. We show that the Goldstone boson exchange
interaction favors these pentaquarks much more than the negative parity ones of
the same flavour content but all quarks in the ground state. We find that the
nonstrange pentaquarks are stable against strong decays.

Assimilation of ARGO temperature profile, sea surface temperature and altimetric satellite data into an eddy permitting primitive equation model of the North Atlantic Ocean
http://hdl.handle.net/2268/165348
Title: Assimilation of ARGO temperature profile, sea surface temperature and altimetric satellite data into an eddy permitting primitive equation model of the North Atlantic Ocean
<br/>
<br/>Author, coauthor: Yan, Yajing; Barth, Alexander; Beckers, JeanMarie; Candille, Guillem; Brankart, JeanMichel; Brasseur, Pierre

Numerical simulation of the electrical characteristics of CIGS/CdS/ZnO solar cell heterostructures
http://hdl.handle.net/2268/165295
Title: Numerical simulation of the electrical characteristics of CIGS/CdS/ZnO solar cell heterostructures
<br/>
<br/>Author, coauthor: Amand, Julien; Nguyen, Ngoc Duy
<br/>
<br/>Abstract: The electrical characteristics of CIGSbased solar cell heterostructure have been simulated by numerically solving the basic semiconductor equations by means of a finite differences method based on a ScharfetterGummel discretization scheme. The electric potential, electric field, carrier concentrations, current densities and recombination rates are obtained as function of the space coordinate and the bias voltage. Starting with the analysis of a single absorber layer structure sandwiched between two metal electrodes, we subsequently studied the properties of the CIGS/ZnO pn heterojunction and the influence of the buffer layer thickness in the CIGS/CdS/ZnO on the cell electrical response. A special focus was also given to the influence of grain boundaries in the bulk of CIGS depending on the defects nature and concentration. Electrical measurements including admittance spectroscopy were performed on samples for comparison to be further lead.
Motivations
This research is part of the project IQuaReS (Innovative inline Quality control for
Renewable Solar solutions) that aims to develop an inline quality control tool for manufactured CIGSbased solar cells, based on electrical and optoelectrical, preferably noninvasive measurement methods. Exploratory simulations aim to isolate signature patterns that could be sought in experimental measurements .

The Threshold Photoelectron Spectrum of Geminal ChloroFluoroethene (1,1C2H2FCl) isomer. Experiment and Theory.
http://hdl.handle.net/2268/165285
Title: The Threshold Photoelectron Spectrum of Geminal ChloroFluoroethene (1,1C2H2FCl) isomer. Experiment and Theory.
<br/>
<br/>Author, coauthor: Locht, Robert; Dehareng, Dominique; Leyh, Bernard
<br/>
<br/>Abstract: The threshold photoelectron spectrum (TPES) of 1,1C2H2FCl has been measured for the first time using synchrotron radiation. It has been compared to the HeI photoelectron spectrum (PES) obtained earlier [Tornow G. et al., Chem.Phys. 146 115 (1990)]. Eight photoelectron bands have been observed at 10.22 eV, 12.45 eV, 13.28 eV, 14.29 eV, 14.99 eV, 17.12 eV, 17.67 eV, and at 20.23 eV successively. Only the first three bands exhibit a rich and extensive vibrational structure. Their adiabatic ionization energies are measured and a detailed vibrational analysis is presented. The assignments of the electronic bands and of the vibrational wavenumbers were made by using ab initio quantum chemical calculations. These allowed us to provide the MO description of the eight electronic states in terms of ionization and double excitation. The good correlation between predicted vibrational wavenumbers and the experimental values provides a strong basis for the assignment of all the vibrational structures.

Dynamical study of the pentaquark antidecuplet
http://hdl.handle.net/2268/165202
Title: Dynamical study of the pentaquark antidecuplet
<br/>
<br/>Author, coauthor: Stancu, Floarea
<br/>
<br/>Abstract: Dynamical calculations are performed for all isomultiplets of the flavour antidecuplet to which the newly discovered pentaquark Theta(+) belongs. The framework is a constituent quark model where the shortrange interaction has a flavourspin structure. In this model the lowest pentaquarks have positive parity. Each antidecuplet member is described by a variational solution with the Pauli principle properly taken into account. By fitting the mass of Theta(+) of minimal content uudd, the mass of Xi(), of minimal content ddss (u) over bar, is predicted at approximately 1960 MeV. The influence of the octetantidecuplet mixing on the masses of the Y = I and 0 pentaquarks is considered within the same model and the role of the hyperfine interaction in this mixing is pointed out. (C) 2004 Elsevier B.V. All rights reserved.

Large Nc baryons and Regge trajectories
http://hdl.handle.net/2268/165200
Title: Large Nc baryons and Regge trajectories
<br/>
<br/>Author, coauthor: Matagne, Nicolas; Stancu, Floarea
<br/>
<br/>Abstract: The mixed symmetric positive and negative parity baryons are described in a similar way in the $1/N_c$ expansion method of QCD by
using a procedure where the permutation symmetry is incorporated exactly. This allows to express the mass formula in terms of a small number of linearly independent operators.
We show that the leading term follows a different Regge
trajectory from that found for symmetric states,
when plotted as a function of the band number $N$.

Artificial Abelian gauge potentials induced by dipoledipole interactions between Rydberg atoms
http://hdl.handle.net/2268/165177
Title: Artificial Abelian gauge potentials induced by dipoledipole interactions between Rydberg atoms
<br/>
<br/>Author, coauthor: Cesa, Alexandre; Martin, John
<br/>
<br/>Abstract: We analyze the influence of dipoledipole interactions between Rydberg atoms on the generation of Abelian artificial gauge potentials and fields. When two Rydberg atoms are driven by a uniform laser field, we show that the combined atomatom and atomfield interactions give rise to nonuniform, artificial gauge potentials. We identify the mechanism responsible for the emergence of these gauge potentials. Analytical expressions for the latter indicate that the strongest artificial magnetic fields are reached in the regime intermediate between the dipole blockade regime and the regime in which the atoms are sufficiently far apart such that atomlight interaction dominates over atomatom interactions. We discuss the differences and similarities of artificial gauge fields originating from resonant dipoledipole and van
der Waals interactions. We also give an estimation of experimentally attainable artificial magnetic fields resulting from this mechanism and we discuss their detection through the deflection of the atomic motion.

Vibrational properties and stabilization mechanism of the amorphous phase of doped GeTe
http://hdl.handle.net/2268/165146
Title: Vibrational properties and stabilization mechanism of the amorphous phase of doped GeTe
<br/>
<br/>Author, coauthor: Raty, JeanYves; Noé, Pierre; Ghezzi, G.; Maîtrejean, S.; Bichara, C.; Hippert, F.
<br/>
<br/>Abstract: Doping chalcogenide phase change materials was shown to improve the stability of the amorphous phase at high temperature and to strongly increase the crystallization temperature. In this work, we use ab initio molecular dynamics together with Fourier transform infrared spectroscopy to address the stabilization of GeTe doped with nitrogen and carbon in the amorphous phase. The comparison between the simulation and experimental results allows indepth understanding of the mechanisms. The inclusion of C and N leads to an increase in high frequency vibrational modes and to a lowering of the boson peak intensity. The reduction of the density of floppy vibrational modes and the computed increase of the mechanical rigidity are responsible for the higher activation energy for crystallization. The mechanism described here could apply more generally to stabilize other GeSbTe phase change materials and ionocovalent glasses at high temperature. © 2013 American Physical Society.

Structure et dynamique de Te et GeTe liquides et amorphes : simulation par dynamique moléculaire ab initio
http://hdl.handle.net/2268/165134
Title: Structure et dynamique de Te et GeTe liquides et amorphes : simulation par dynamique moléculaire ab initio
<br/>
<br/>Author, coauthor: Raty, JeanYves; Malcioglu, Osman Baris; Bichara, Christophe
<br/>
<br/>Abstract: Contrairement à la plupart des éléments, les phases liquide et amorphe du tellure se sont avérées être assez mal reproduites par la méthode, pourtant éprouvée, de la dynamique moléculaire ab initio . Les calculs ‘standart’ utilisant la théorie de la fonctionnelle de la densité (DFT) produisent en effet des structures en relatif désaccord avec les expériences de diffraction, en particulier pour ce qui concerne le nombre de premiers voisins et les distances interatomiques, quantités qui apparaissent fortement surestimées dans les simulations. Le tellure étant composant essentiel de la plupart des matériaux à changement de phase (PCMs), cette mauvaise description de ses phases désordonnées soulève d’importantes questions au sujet de la capacité de la dynamique moléculaire ab initio à générer des structures d’amorphe réalistes pour les PCMs.
Dans ce travail, nous utilisons la dynamique moléculaire ab initio réalisée à volume constant (valeurs expérimentales) pour simuler la structure et la dynamique du tellure liquide le long de l’anomalie de densité. Nous testons différentes approximations afin de démontrer leur importance sur la structure du liquide et de l’amorphe. En particulier, si l’interaction spinorbite apparaît au final avoir un effet neutre, le traitement des forces de dispersion fournit une nette amélioration visàvis de calculs récents utilisant des fonctionnelles hybrides, l’ordre atomique local étant fortement modifié dans les deux phases [1]. L’évolution de la structure avec l’anomalie de densité est clairement reliée à la création de nombreuses interconnections entre chaines de tellure, ces chaines étant de plus en plus longues avec l’abaissement de la température. Dans la phase amorphe, les chaines sont pratiquement intactes et présentent des distributions d’angle dièdre originales. Ces modifications sont reflétées dans les propriétés dynamiques, telles que le coefficient de diffusion et la densité d’états vibrationnels.
[1] J. Akola, R. O. Jones, S. Kohara, T. Usuki, and E. Bychkov, Phys. Rev. B 81, 094202 (2010).

The role of C and N dopants incorporation in phase change materials
http://hdl.handle.net/2268/165129
Title: The role of C and N dopants incorporation in phase change materials
<br/>
<br/>Author, coauthor: Noé, Pierre; Raty, JeanYves; Ghezzi, Giada; Hippert, Françoise; Fillot, F.; Gourvest, E.; Souchier, E.; Perniola, L.; Sousa, Valérie; Hubert, Q.; Persico, A.; Henaff, E.; Tessaire, M.; Delaye, V.; Bichara, C.; Maitrejean, S.
<br/>
<br/>Abstract: Phase change memory (PCM) technology is considered to be among the most promising alternatives to conventional technologies in embedded memories [1]. To allow operation at relatively high temperatures in embedded applications, it is crucial to improve the stability of the amorphous phase. Carbon and nitrogen doping have been shown to significantly increase the crystallization temperature [13]. Moreover, the high RESET current requirement [2], which is a limit to the scalability of GeTe and GST, can be reduced by the incorporation of a dopant element [4].
In this presentation we focus on correlating experimental results and ab initio simulations to understand the effect of C and N incorporation in GeTe and GST PCM devices. Understanding the effect of dopants on the change of electronic properties and the mechanisms of the phase transformation requires analysis of the local order and structure of the amorphous to crystalline phases.
In this context, we demonstrate that carbon and nitrogen deeply affects the structure and the dynamical properties of the amorphous phase of GeTe. In particular, the inclusion of N and C dopant elements in GeTe has a drastic effect on the vibrational modes of GeTe therefore improving the stability of the glass. This effect goes with an increased mechanical rigidity explaining why these doped GeTe compounds have a higher crystallization temperature than the undoped ones.
Finally we will explore, mainly by FTIR and XRD measurements, the effect of C and N dopants during the annealing of amorphous PCMaterials towards their crystalline phases. These results will be discussed in order to understand the origin of the differences of the doped PCMaterials amorphous phase stability (data retention) observed between full sheet materials and the materials integrated in PCM devices.
[1] A. Fantini et al., 2010 IEEE International Electron Devices Meeting (IEDM), 2010, pp. 29.21.2129.21.24.
[2] G. Betti Beneventi et al., SolidState Electronics, 6566 (2011) 197204.
[3] V. Sousa et al., EPCOS 2011.
[4] Q. Hubert et al., IMW 2012.
<br/>
<br/>Commentary: Abstract EE15.02

Structure, dynamical properties and topology of GST phase change materials
http://hdl.handle.net/2268/165123
Title: Structure, dynamical properties and topology of GST phase change materials
<br/>
<br/>Author, coauthor: Raty, JeanYves; Bichara, Christophe
<br/>
<br/>Abstract: GeSbTe alloys (GST) have been successfully used as Phase Change Materials for data recording applications. They exhibit a unique collection of properties that make them adequate for high performance nonvolatile RAM memories. Indeed, their crystalline phase(s) are extremely contrasted, both optically and electrically, against their easily generated amorphous phase(s).
Understanding the fast switching mechanisms and the amorphous phase properties remains however quite challenging. In particular, the stability of the amorphous phase against phase separation, recrystallization, and drift of the electronic properties with time and cycling remain problematic. In this work, we generate models of a series of amorphous GST alloys using DFT molecular dynamics and simulated annealing. The obtained structures are compared and generic patterns are described. A new algorithm to determine the topological constraints, based on the analysis of the fluctuations of interatomic bond lengths and bond angles, has been proposed and applied to seven alloy compositions in the GeSbTe phase diagram [1]. A constraint map could then be drawn for the whole ternary system. According to this, the most commonly used GST amorphous phases are shown to be in the stressed rigid region [1]. In order to estimate the effect of rigidity on the recrystallization temperature (Tc), we performed a similar study for Carbon and Nitrogen doped GeTe [2]. The increase of the number of constraints upon doping is shown to be correlated with an increase of the recrystallization temperature and a reduction of the low frequency, or floppy, vibrational modes [3]. The generality of this stabilization mechanism is finally tested on other systems.
[1] M. Micoulaut, J.Y. Raty, C. Otjacques, and C. Bichara, Physical Review B 81 (2010) 174206
[2] G. Ghezzi, J.Y. Raty, S. Maitrejean, A. Roule, E. Elkaim and F. Hippert, Applied Physics Letters, 99 (2011) 151906.
[3] J.Y. Raty, P. Noe, G.Ghezzi, S. Maitrejean, C. Bichara and F. Hippert. To be published.

Local order, dynamics and stability of C and N doped phase change materials
http://hdl.handle.net/2268/165120
Title: Local order, dynamics and stability of C and N doped phase change materials
<br/>
<br/>Author, coauthor: Hippert, Françoise; Raty, JeanYves; Noé, Pierre; Ghezzi, Giada; Maîtrejean, Sylvain
<br/>
<br/>Abstract: Doping Chalcogenide Phase Change Materials, such as Ge2Sb2Te5 and GeTe used in nonvolatile phase change memories, was shown to improve the stability of the amorphous phase and to strongly increase the crystallization temperature. We combined total Xray
scattering experiments [1], Fourier Transform InfraRed (FTIR) spectroscopy and ab initio Molecular Dynamics simulations to address the stabilization of the amorphous phase of
GeTe doped with Carbon or Nitrogen. The comparison between the simulation and exp
erimental results allows in depth understanding of the role of dopants. They deeply modify the structure of the amorphous phase by introducing tetrahedral units centered on C or N, triangular environments and short C chains in Cdoped GeTe, NGe3 pyramids and N2
molecules in Ndoped GeTe. One major difference between N and C doping is the fact that C can form short bonds with Te, although in smaller proportion than CGe, while short NTe bonds are absent in Ndoped GeTe. The inclusion of C or N leads to an increase in high frequency vibrational modes, to a reduction of the density of floppy vibrational modes that drive the crystallization and to an increase of the rigidity. This stabilization mechanism could
apply more generally to various GST materials as well as to other ionocovalent glasses.
[1] G.E. Ghezzi, J.Y.Raty, S. Maitrejean, A. Roule, E. Elkaim and F. Hippert, Appl. Phys. Lett.
99 (2011) 151906
<br/>
<br/>Commentary: LO.05

Ab Initio Molecular Dynamics Simulation of Liquid and Amorphous Te
http://hdl.handle.net/2268/165118
Title: Ab Initio Molecular Dynamics Simulation of Liquid and Amorphous Te
<br/>
<br/>Author, coauthor: Raty, JeanYves; Malcioglu, Osman Baris; Bichara, Christophe
<br/>
<br/>Abstract: Contrary to almost all other elements, liquid and amorphous phases of pure tellurium have proven difficult to simulate using ab initio molecular dynamics. Standard density functional theory calculations yield structures in relatively poor agreement with available diffraction experiments at low temperature, especially regarding first neighbor distance and coordination number, which are strongly overestimated in the simulations. Tellurium being a key component of many phase change materials, this poor structural description of its disordered phases raises important issues about the ability of ab initio molecular dynamics to generate accurate structural models of amorphous phases.
In this work, we use ab initio molecular dynamics performed under constant volume (experimental values) conditions to simulate liquid Tellurium structure and dynamics along its density anomaly. We test different exchange correlation functionals and approximations, and show their influence on liquid and amorphous structures. In particular, we show that the treatment of dispersion forces is yielding a clear improvement over recent hybrid functional calculations [1], with significant local order modifications in both phases. Especially, the structure evolution along the density anomaly is shown to be related to the creation of many interconnections between Te chains, these chains having increasing lengths upon temperature reduction. In the amorphous phase, Te chains are almost perfectly isolated with specific dihedral angle distributions. These structural changes are reflected on dynamical properties, such as atomic diffusion coefficient and vibrational density of states. We then apply the same method to revisit the structure of some Te based alloys.
[1] J. Akola, R. O. Jones, S. Kohara, T. Usuki, and E. Bychkov, Phys. Rev. B 81, 094202 (2010).

[70,l+] baryons in large Nc QCD revisited: The effect on Regge trajectories
http://hdl.handle.net/2268/165087
Title: [70,l+] baryons in large Nc QCD revisited: The effect on Regge trajectories
<br/>
<br/>Author, coauthor: Matagne, Nicolas; Stancu, Floarea
<br/>
<br/>Abstract: A simple procedure within the 1/N_c expansion method where all the N_c
quarks are treated on the same footing has been found successful in describing mixed symmetric negative parity baryon states belonging to the [{\bf 70},\ell^] multiplets of the N = 1 and 3 bands. Presently it is applied to mixed symmetric positive parity [{\bf 70},0^+] and [{\bf 70},2^+] multiplets of the N = 2 band. We search for the most dominant terms in the mass formula. The results are compared to those obtained in the procedure where the system is separated into a core and an excited quark. We find that both the spin and isospin operators of the entire system of N_c quarks play dominant roles in describing the data, like for negative parity states. As a byproduct we present the contribution of the leading spinisospin singlet term as a function of the band number, which hints at distinct Regge trajectories for the symmetric and mixed symmetric states.

Controllable morphology of flux avalanches in microstructured superconductors
http://hdl.handle.net/2268/164944
Title: Controllable morphology of flux avalanches in microstructured superconductors
<br/>
<br/>Author, coauthor: Motta, M.; Colauto, F.; Vestgarden, J.I.; Fritzsche, J.; Timmermans, M.; Cuppens, J.; Attanasio, C.; Cirillo, C.; Moshchalkov, V.V.; Van de Vondel, J.; Johansen, T.H.; Ortiz, W.A.; Silhanek, Alejandro
<br/>
<br/>Abstract: The morphology of abrupt bursts of magnetic flux into superconducting films with engineered
periodic pinning centers (antidots) has been investigated. Guided flux avalanches of thermomagnetic origin develop a treelike structure, with the main trunk perpendicular to the borders of the sample, while secondary branches follow welldefi ned directions determined by the geometrical details of the underlying periodic pinning landscape. Strikingly, we demonstrate that in a superconductor with relatively weak random pinning, the morphology of such flux avalanches can be fully controlled by proper combinations of lattice symmetry and antidot geometry. Moreover, the resulting flux patterns can be reproduced, to the fi nest details, by simulations based on a phenomenological thermomagnetic model. In turn, this model can be used to predict such complex structures and to estimate physical variables of more di fficult experimental access, such as the local values of temperature and electric fi eld.

Influence of dipoledipole interactions decoherencefree states
http://hdl.handle.net/2268/164714
Title: Influence of dipoledipole interactions decoherencefree states
<br/>
<br/>Author, coauthor: Damanet, François; Martin, John
<br/>
<br/>Abstract: Decoherence, known as the consequence of the coupling of any quan
tum system to its environment, causes information loss in the system
and represents a major problem in the physical realization of quan
tum computers [1]. DecoherenceFree States (DFS) are considered as a
possible solution to this problem. A set of trapped cold atoms placed
in a DFS state will be immune against decoherence due to sponta
neous emission. However, because of dipoledipole interactions between
atoms, induced dephasing effects are likely to destroy the coherence
and drive the system out of its DFS [12]. In this work, we study nu
merically the dynamics of a set of twolevel atoms initially in a DFS
with respect to dissipative processes by solving the master equation in
cluding both dissipative dynamics and dipole dipole interactions. We
focus our attention on the influence of dipolar coupling on the radiated
energy rate and coherence of the system as in [3]. In particular, by av
eraging over many realizations of close randomly distributed atomic
positions, we show the formation of a superradiantlike pulse and we
study its properties as a function of the dipolar coupling strength.
[1] D. A. Lidar & K. B. Whaley, Lectures Notes in Phys., Vol. 622,
p83120, Springer (2003).
[2] M. Gross & S. Haroche, Physics reports 93, 301396 (1982).
[3] W. Feng, Y. Li & S. Y. Zhu, arXiv :1302.0957. (2013).