Auswahl der wissenschaftlichen Literatur zum Thema „Système quantique de spins“
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Zeitschriftenartikel zum Thema "Système quantique de spins"
Guidoni, Luca, Marie Houssin und Jean-Philippe Karr. „Spectroscopie haute résolution : l’apport des ions piégés refroidis par laser“. Photoniques, Nr. 121 (2023): 47–51. http://dx.doi.org/10.1051/photon/202312147.
Der volle Inhalt der QuelleVan Helden, Alice. „interprétation relationnelle de la physique quantique“. Revue des questions scientifiques 193, Nr. 1-2 (01.01.2022): 95–116. http://dx.doi.org/10.14428/qs.v193i1-2.70223.
Der volle Inhalt der QuelleAntoine, Jean-Pierre. „Symétries en physique“. Revue des questions scientifiques 190, Nr. 1-2 (01.01.2019): 7–26. http://dx.doi.org/10.14428/qs.v190i1-2.69423.
Der volle Inhalt der QuelleSmigiel, Eddie, und François de Bertrand de Beuvron. „Enseigner les Systèmes Numériques en 2049“. J3eA 21 (2022): 2003. http://dx.doi.org/10.1051/j3ea/20222003.
Der volle Inhalt der QuelleVitrac, Richard. „La théorie de la relativité cognitive et systémique“. Acta Europeana Systemica 7 (11.07.2020): 179–96. http://dx.doi.org/10.14428/aes.v7i1.56733.
Der volle Inhalt der QuelleCarrive, Laurent. „De la réalité des modèles et des théories“. Acta Europeana Systemica 4 (14.07.2020): 89–98. http://dx.doi.org/10.14428/aes.v4i1.57283.
Der volle Inhalt der QuelleDissertationen zum Thema "Système quantique de spins"
Forestier, Guillaume. „Transport quantique dans les verres de spins“. Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY023/document.
Der volle Inhalt der QuelleThe experiments presented in this thesis associate two fields of condensed matter physic, on the one hand with the spin glass physic and the other hand with the mesoscopic physic. The spin glass state is one of the most emblematic of disordered and frustred system and at low temperature, it is caracterized by an unconventionel order where the magnetic disorder is quenched. Moroever, it is considered as a model system for glasses in general and thereby it has been extensively studied, both experimentally and theoreticlly. After extensive research efforts, the description of fundamental state of the system has lead towards two well different approaches. The first, given by the mean field solution, highlights a fundamental composed of mulitple states organised and hierarchical. The second, called droplet model is based on the off--equilibrium dynamic of a unique ground state. However, despite these contributions, the understanding ot this phase is far from being complete and the nature of the ground state still remains an open question. In a mesoscopic conductor, the transport of electron is coherent: electrons keep the memory of their phase, so that one can observe interference effects. The main motivation of this work is to use these interference effects in order to to probe the spin glass state. Indeed, as electronic interference depends of the position of the static disorder, coherent transport can be a useful tool to study the configuration of the microscopic disorder. Althought few coherent transport experiments exist to probe the spin glass, this field of research has very little explored. Nevertheless, this area has been a revival thanks to theoritical work, showing how coherent transport is sensitived to the quenched disorder and how it may provide informations of the nature of fundamental state of spin glass. So, this experimental work deals with the implementation of transport measurements in mesoscopic spin glasses. The first part of the study is focused on the general charateristics of classical and quatum transport of these system. We have examined the resistivity as a function of the temperature and magnetic field and we show that these mesoscopic systems have a spin glass-like behaviour. In a second part, we have focused on the low field magnetoresistivity. We show that it presents a strong hysteresis, whose the amplitude is strongly depends, both of the temperature in the glassy phase and sweeping rate of the magnetic field. We argue that this particular behaviour is related to the out off-equilibrium of the system and we show how the temperature and the sweeping rate control the deviation to the equilibrium. In this part, we also examine by transport measurements how the system relaxes towards the equilibrium just after its excitation. In addition, we present surprinsing transport propreties that we observed, resulting of experimental protocols more sophisticated in temperatures and magnetic fields
Clémancey, Martin. „Etude RMN du système de spins quantiques CuHpCl“. Université Joseph Fourier (Grenoble), 2004. http://www.theses.fr/2004GRE10037.
Der volle Inhalt der QuelleWe present an NMR study of magnetic properties of Cu2(C5H12N2)2Cl4(CuHpCl). This system of quantum spins 1/2 has been considered for a long time as an experimental realization of a spin ladder system. Its phase diagram under magnetic field is very rich, in particular a spin liquid ground state in zero field and two quantum phase transitions at Hcl=7. 5Tesla and Hc2=13Tesla. The first goal of this study was a clarification of some specific parts of the phase diagram, in particular the low temperature regime beetwen Hcl and Hc2, where tridimensional magnetic order sets in. Trought the study of a compound deuterated on specific hydrogen bonds, we observed the commensurate nature of this ordered phase. The second-order phase transition was studied as a function of H and T. The main result of this study interactions, like observed in other spin liquid componds like NENP or SrCu(Bo3). This "anomalus" staggered magnetisation 3D magnetic order can be observed. We also observed by torque magnetometry anomalous features due to this staggered magnetisation. Last, in order to understand the magnetic exchange pathways in CuHpCl, we also undertook NMR and torque measurements of methylated of CuHpCl
Dimo, Panjio Claude. „Étude des modèles de Richardson-Gaudin de spin-½ avec champ magnétique arbitraire“. Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0154.
Der volle Inhalt der QuelleThis thesis is divided into three parts and extended over seven chapters between the general introduction and conclusion. Indeed, the first part, consisting of four chapters, is mainly focused on a static study of Richardson-Gaudin models of spin 1/2 with arbitrary magnetic field including the possibility of a totally anisotropic XYZ coupling such that the terms "S^x_jS^x_k , S^y_j S^y_k mathrm{and} S^z_j S^z_k" all have distinct coupling strengths. In this part we determine generically the energy spectrum, the central spin mean values, the wave functions and the two-point correlation functions of the considered models; which will be useful for an advanced dynamical analysis of these models. The calculation of the energy spectrum of the current system can exploit its integrability which is materialized by a set of equations constituting the integrability condition. This calculation is done independently of the symmetry of the model considered and involves the resolution of a system of quadratic equations that is relatively simple to solve numerically.The second part focuses on some examples of applications that could be implemented on the basis of the results obtained in part I. Indeed, it has recently been shown that the XX central spin model is integrable. It describes a particular spin coupled via XX spin-spin couplings to a bath of other spins while feeling a magnetic field along the "hat{z}" axis, i.e. perpendicular to the plane in which the coupling exists. What interests us here is first to demonstrate that the XX central spin model remains integrable in the presence of an arbitrarily oriented magnetic field. In a second step we study whether the dark states remain in this case. The U(1) symmetry of the considered model is broken by the addition of an external field component in the XY plane, which could lead to a radically different physics. Nevertheless, we show that, for a sufficiently strong coupling, the structure of the dark states reappears even in the presence of a magnetic field in the plane. A simple understanding of this result and the demonstration of the universality of the results by a finite size scale study and for a variety of distinct distributions of the coupling constants at the different spins of the bath. Another example of application which closes this second part is that of the XXX dark states with arbitrary magnetic field. These states, although having a different physics from the one encountered in the previously studied models, exist and a generic law has been established to count them.This law has been verified up to 12 spins in the bath, so we can assume that it also works beyond 12 spins in the bath, we can conjecture that it is valid for any value of N.The third part of this project is dedicated to a dynamic study of non-integrable models similar to those studied in the first part of this manuscript. Indeed, these models are just the representation of Richardson-Gaudin models immersed in a time dependent magnetic field oriented along "hat{z}".In a process of rotation around the "hat{z}" axis of the magnetic field associated to the central spin, it is possible to define a time dependent basis in which the time dependent problem reduces to an independent problem. The resulting Hamiltonian can then be integrable and require the use of the results found in the first part to be solved. For these models, by imagining for example that the system is initially prepared in a dark state of the static Hamiltonian, we clearly see that its dynamics is not trivial and leads to perfect oscillations of this state.Finite size systems resulting from the central spin models treated in this thesis depend strongly on the distribution of couplings between the central spin and each nuclear spin constituting the bath
Platini, Thierry. „Chaînes de spins quantiques hors de l'équilibre“. Phd thesis, Université Henri Poincaré - Nancy I, 2008. http://tel.archives-ouvertes.fr/tel-00439896.
Der volle Inhalt der QuelleAtas, Yasar Yilmaz. „Quelques aspects du chaos quantique dans les systèmes de N-corps en interaction : chaînes de spins quantiques et matrices aléatoires“. Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112221/document.
Der volle Inhalt der QuelleMy thesis is devoted to the study of some aspects of many body quantum interacting systems. In particular we focus on quantum spin chains. I have studied several aspects of quantum spin chains, from both numerical and analytical perspectives. I addressed especially questions related to the structure of eigenfunctions, the level densities and the spectral properties of spin chain Hamiltonians. In this thesis, I first present the basic numerical techniques used for the computation of eigenvalues and eigenvectors of spin chain Hamiltonians. Level densities of quantum models are important and simple quantities that allow to characterize spectral properties of systems with large number of degrees of freedom. It is well known that the level densities of most integrable models tend to the Gaussian in the thermodynamic limit. However, it appears that in certain limits of coupling of the spin chain to the magnetic field and for finite number of spins on the chain, one observes peaks in the level density. I will show that the knowledge of the first two moments of the Hamiltonian in the degenerate subspace associated with each peak give a good approximation to the level density. Next, I study the statistical properties of the eigenvalues of spin chain Hamiltonians. One of the main achievements in the study of the spectral statistics of quantum complex systems concerns the universal behaviour of the fluctuation of measure such as the distribution of spacing between two consecutive eigenvalues. These fluctuations are very well described by the theory of random matrices but the comparison with the theoretical prediction generally requires a transformation of the spectrum of the Hamiltonian called the unfolding procedure. For many-body quantum systems, the size of the Hilbert space generally grows exponentially with the number of particles leading to a lack of data to make a proper statistical study. These constraints have led to the introduction of a new measure free of the unfolding procedure and based on the ratio of consecutive level spacings rather than the spacings themselves. This measure is independant of the local level density. By following the Wigner surmise for the computation of the level spacing distribution, I obtained approximation for the distribution of the ratio of consecutive level spacings by analyzing random 3x3 matrices for the three canonical ensembles. The prediction are compared with numerical results showing excellent agreement. Finally, I investigate eigenfunction statistics of some canonical spin-chain Hamiltonians. Eigenfunctions together with the energy spectrum are the fundamental objects of quantum systems: their structure is quite complicated and not well understood. Due to the exponential growth of the size of the Hilbert space, the study of eigenfunctions is a very difficult task from both analytical and numerical points of view. I demonstrate that the groundstate eigenfunctions of all canonical models of spin chain are multifractal, by computing numerically the Rényi entropy and extrapolating it to obtain the multifractal dimensions
Dillenschneider, Raoul. „Effects of a strict site-occupation constraint in the description of quantum spin systems at finite temperature“. Université Louis Pasteur (Strasbourg) (1971-2008), 2006. https://publication-theses.unistra.fr/public/theses_doctorat/2006/DILLENSCHNEIDER_Raoul_2006.pdf.
Der volle Inhalt der QuelleWendenbaum, Pierre. „Intrication et dynamique de trempe dans les chaînes de spins quantiques“. Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0170/document.
Der volle Inhalt der QuelleThe study carried in this thesis concerns the dynamics of out-Of-Equilibrium quantum systems, and more particularly their entanglement properties. Indeed, entanglement became a fundamental concept in modern physics, especially with the development of quantum information. We have in a first part studied the dynamics of a model of bosons on a lattice after the quench of their trapping potential. In the hard-Core limit, we developed an hydrodynamical theory which perfectly reproduced the observed behavior. Then, we have looked at the dynamics of two defect spins coupled to an Ising chain. When these defects have been prepared into a separable state, we have established a formula giving the evolution of the reduced density matrix, allowing us to have access to the entanglement create through the coupling to the chain. We considered then the case of two initially entangled defect spins, and we studied the influence of a non-Equilibrium environment on the disentanglement properties. Finally, the last part of this thesis is devoted to the study of a system coupled to an environment by means of the repeated interactions process. We studied the relaxation of the system in two different time regimes. For short times, the state is well described by a non-Equilibrium-Steady-State, in which we highlighted the scaling properties of some observables. For long times, the system reaches an equilibrium steady state made of a product of Bell states
Anfray, Valentin. „Étude numérique du point critique de systèmes quantiques de spin désordonnés en dimensions élevées“. Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0127.
Der volle Inhalt der QuelleSeveral random quantum spin models have been numerically studied in dimension D>1 by Strong Disorder Renormalisation Group (SDRG). We have implemented an efficient algorithm to be able to consider a system with up to a billion spins independently of its spatial dimension. Critical properties of the 2D and 3D random quantum Potts model with q=2,3,5,10,20 and 50 states are shown to be governed by an infinite disorder fixed point. We have computed the correlation-length exponent u, the magnetization exponent d_f and the energy gap exponent psi. Using finite-size scaling and taking into account finite-size corrections, critical properties of the Potts model are shown to be q-independent. Random quantum Clock models with q=2,3,5,8 and 10 states have been also studied in 2D and 3D. A minimum amount of initial disorder strength is required to flow to an infinite disorder fixed point. Despite large error bars on psi exponent, our estimates for the critical exponents u and psi for all q are compatible with those of the random transverse-field Ising model. Our estimates for the critical exponent d_f are incompatible within error bar but very close. Lastly, the tricritical point of the random quantum Ashkin-Teller model has been studied in dimension two and three. We have shown that the correlation-length exponent associated with one of the two unstable directions does not belong to the university class of the random transverse-field Ising model
Bocquet, Marc. „Chaînes de Spins, Fermions de Dirac, et Systèmes Désordonnés“. Phd thesis, Ecole Polytechnique X, 2000. http://tel.archives-ouvertes.fr/tel-00001560.
Der volle Inhalt der QuelleCapron, Thibaut. „Transport quantique dans les verres de spin“. Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00686330.
Der volle Inhalt der QuelleBücher zum Thema "Système quantique de spins"
Kinslow, Frank J. Le système quantique de Kinslow. Paris: Le Courrier du livre, 2015.
Den vollen Inhalt der Quelle findenPilote, Lomer. Les faussetés d'Einstein et de la théorie quantique: Système spirituel mathématico-philosophique. Montréal: Éditions Quebecor, 2012.
Den vollen Inhalt der Quelle findenN, Christopeit, Helmes K und Kohlmann M, Hrsg. Stochastic differential systems: Proceedings of the 3rd Bad Honnef conference, June 3-7, 1985. Berlin: Springer-Verlag, 1986.
Den vollen Inhalt der Quelle findenBuchteile zum Thema "Système quantique de spins"
„L'état d'un système“. In Comprendre la mécanique quantique, 137–48. EDP Sciences, 2001. http://dx.doi.org/10.1051/978-2-7598-0175-6.c016.
Der volle Inhalt der Quelle„IV APPLICATION DES POSTULATS À DES CAS SIMPLES : SPIN 1/2 ET SYSTÈMES À DEUX NIVEAUX“. In Mécanique Quantique - Tome 1, 397–500. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2288-1-006.
Der volle Inhalt der Quelle„IV APPLICATION DES POSTULATS À DES CAS SIMPLES : SPIN 1/2 ET SYSTÈMES À DEUX NIVEAUX“. In Mécanique Quantique - Tome 1, 397–500. EDP Sciences, 2020. http://dx.doi.org/10.1051/978-2-7598-2288-1.c006.
Der volle Inhalt der Quelle„Chapitre 4 Corrigés des exercices du Chapitre IV (Complément JIV). Application des postulats à des cas simples : spin 1/2 et systèmes à deux niveaux“. In Corrigés des exercices de Mécanique Quantique tome 1, 173–226. EDP Sciences, 2023. http://dx.doi.org/10.1051/978-2-7598-3160-9.c004.
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