Rozprawy doktorskie na temat „Fermionic lattice models”
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Agostinelli, Chiara. "Edge states and zero modes in quadratic fermionic models on a 1-D lattice". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9344/.
Pełny tekst źródłaStenzel, Leo Johannes Martin [Verfasser], i Ulrich [Akademischer Betreuer] Schollwöck. "Quantum Hall effect in interacting fermionic lattice models / Leo Johannes Martin Stenzel ; Betreuer: Ulrich Schollwöck". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1225683025/34.
Pełny tekst źródłaLinnér, Erik. "Interplay of collective fluctuations in strongly correlated fermionic systems". Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAX090.
Pełny tekst źródłaStrongly correlated systems often display rich phase diagrams exhibiting different ordered phases involving spin, charge, pairing, or orbital degrees of freedom. The theoretical description of the competition between different instabilities in strongly correlated systems giving rise to this phenomenology, remains one of the holy grails of modern condensed matter theory. It poses a tremendous challenge of both conceptual and computational complexity, and thus the interplay of competing electronic fluctuations constitutes a roadblock to the understanding of the complex phase diagrams of a wide range of correlated quantum materials. This motivates the search for constructing simplified methods to study interplaying collective fluctuations.We introduce a multichannel extension of the recently developed fluctuating field approach to competing collective fluctuations in correlated electron systems. The method is based on a variational optimization of a trial action that explicitly contains the order parameters of the leading fluctuation channels. It gives direct access to the free energy of the system, facilitating the distinction between stable and metastable phases of the system.We apply our approach to the extended Hubbard model, a paradigmatic fermionic lattice model, occupying a prime place in condensed matter theory due to the potential relevance of its repulsive and attractive versions for both electronic materials and artificial systems.Utilising the technique to study the weak to intermediate coupling regime of the repulsive interaction, we find it to capture the interplay of competing charge density wave and antiferromagnetic fluctuations with qualitative agreement with more computationally expensive methods. In addition, the method allows access to excited-state properties, through the one-particle excitation spectrum, and many-body correlation effects, through the self-energy, directly on the real-frequency axis without using numerical analytic continuation techniques. The multichannel fluctuating field approach thus offers a promising route for a numerically low-cost treatment of the interplay between collective fluctuations in small to large systems.Using the introduced multichannel fluctuating field approach, we explore the phase diagram of the extended Hubbard model in both repulsive and attractive regimes, addressing the interplay of fluctuations in the antiferromagnetic, charge density wave, s-wave superconducting, and phase separation channels. Despite the fact that this model has been intensively studied for decades, our novel approach allows us to identify a novel phase that is characterised by the coexistence of collective s-wave superconducting and phase separation fluctuations. These findings resonate with previous observations of interplaying phase separation and superconducting phases in electronic systems, most importantly in high-temperature superconductors. In addition, the multichannel fluctuating field method allows to display the quintessential nature of the extended Hubbard model through the large variety of types of competitions which emerges from the interplaying instabilities. The general nature of the proposed theory, allowing to incorporate a variety of collective modes, makes it a promising tool for studying the interplay of collective fluctuations in strongly correlated fermionic systems
Bougenaya, Yamina. "Fermion models on the lattice and in field theory". Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7080/.
Pełny tekst źródłaZverev, Nikolai. "Algorithmic studies of compact lattice QED with Wilson fermions". Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963575082.
Pełny tekst źródłaKhamseh, Ava. "Lattice phenomenology of heavy quarks using dynamical fermions". Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28855.
Pełny tekst źródłaPlaum, Wätzold. "Numerical analysis using Generalised Pattern Search for a discrete fermionic lattice model of the vacuum". kostenfrei, 2009. http://epub.uni-regensburg.de/13587/.
Pełny tekst źródłaBjörnson, Kristofer. "Topological band theory and Majorana fermions : With focus on self-consistent lattice models". Doctoral thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-305212.
Pełny tekst źródłaGramsch, Christian [Verfasser], i Michael [Akademischer Betreuer] Potthoff. "A Memory-Kernel-Free Approach to Time-Dependent Lattice Fermion Models / Christian Gramsch ; Betreuer: Michael Potthoff". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1153884186/34.
Pełny tekst źródłaBozzato, Luca. "Two dimensional Kitaev model with long-range pairing". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13442/.
Pełny tekst źródłaO'Brien, Aroon. "Charge degrees of freedom on the kagome lattice". Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-71860.
Pełny tekst źródłaRizzi, Matteo. "Quantum Phase transitions in Hubbard lattices". Doctoral thesis, Scuola Normale Superiore, 2007. http://hdl.handle.net/11384/85848.
Pełny tekst źródłaAsadzadeh, Mohammad Zhian. "Interplay of Superconductivity and Magnetism in the Two Dimensional Kondo Lattice Model". Doctoral thesis, SISSA, 2013. http://hdl.handle.net/20.500.11767/4818.
Pełny tekst źródłaLeder, Björn. "The Schrödinger functional for Gross-Neveu models". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15660.
Pełny tekst źródłaGross-Neveu type models with a finite number of fermion flavours are studied on a two-dimensional Euclidean space-time lattice. The models are asymptotically free and are invariant under a chiral symmetry. These similarities to QCD make them perfect benchmark systems for fermion actions used in large scale lattice QCD computations. The Schrödinger functional for the Gross-Neveu models is defined for both, Wilson and Ginsparg-Wilson fermions, and shown to be renormalisable in 1-loop lattice perturbation theory. In two dimensions four fermion interactions of the Gross-Neveu models have dimensionless coupling constants. The symmetry properties of the four fermion interaction terms and the relations among them are discussed. For Wilson fermions chiral symmetry is explicitly broken and additional terms must be included in the action. Chiral symmetry is restored up to cut-off effects by tuning the bare mass and one of the couplings. The critical mass and the symmetry restoring coupling are computed to second order in lattice perturbation theory. This result is used in the 1-loop computation of the renormalised couplings and the associated beta-functions. The renormalised couplings are defined in terms of suitable boundary-to-boundary correlation functions. In the computation the known first order coefficients of the beta-functions are reproduced. One of the couplings is found to have a vanishing beta-function. The calculation is repeated for the recently proposed Schrödinger functional with exact chiral symmetry, i.e. Ginsparg-Wilson fermions. The renormalisation pattern is found to be the same as in the Wilson case. Using the regularisation dependent finite part of the renormalised couplings, the ratio of the Lambda-parameters is computed.
Meyer, Karsten. "Flussgleichungen für das Anderson-Gitter zur Beschreibung von Schwer-Fermion-Systemen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1079709122000-46905.
Pełny tekst źródłaThe physical properties of heavy-fermion systems are examined. These systems are mainly formed by rare earth or actinide compounds. Their essential physics can be characterized by the periodic Anderson model which describes the interplay of itinerant metal electrons and localized, but strongly correlated f-electrons. The present calculations are based on the flow equations approach proposed by Wegner. This method uses a continuous unitary transformation to derive an effective Hamiltonian of an easy to treat structure. Within this framework the electronic structure of heavy-fermion systems is calculated and the influence of external parameters is studied. Beside the derivation of static properties the density of states and dynamic magnetic susceptibilities are investigated in order to characterize the nature of collective excitations
Meyer, Karsten. "Flussgleichungen für das Anderson-Gitter zur Beschreibung von Schwer-Fermion-Systemen". Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24313.
Pełny tekst źródłaThe physical properties of heavy-fermion systems are examined. These systems are mainly formed by rare earth or actinide compounds. Their essential physics can be characterized by the periodic Anderson model which describes the interplay of itinerant metal electrons and localized, but strongly correlated f-electrons. The present calculations are based on the flow equations approach proposed by Wegner. This method uses a continuous unitary transformation to derive an effective Hamiltonian of an easy to treat structure. Within this framework the electronic structure of heavy-fermion systems is calculated and the influence of external parameters is studied. Beside the derivation of static properties the density of states and dynamic magnetic susceptibilities are investigated in order to characterize the nature of collective excitations.
Binz, Benedikt. "Weak-coupling instabilities of two-dimensional lattice electrons". Phd thesis, Université Paris-Diderot - Paris VII, 2002. http://tel.archives-ouvertes.fr/tel-00001981.
Pełny tekst źródłaSilva, Junior José Luiz Ferreira da. "Efeito Kondo e magnetismo em uma rede Kagome". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/53142.
Pełny tekst źródłaIn this work we study the Kondo Lattice model for the kagome lattice, in order to understand better the effects of geometrical frustration in heavy-fermion systems. In this context, we consider a mean field scheme valid for all the system’s phases. Firstly, we analyzed the nonmagnetic case. In this approximation the electron energies and spectral functions are reachable, then we use the density of states to calculate the occupations selfconsistently. Our results are qualitatively compared with previous works in other geometries. In the second part we introduce an approximation for magnestism, which takes into account the mean field scheme considered and the presence of geometrical frustration. Self-consistent calculations are done through the frequencies summation method. Our results show that the magnetism is supressed when the temperature is increased or the band filling deviates from half-filling. Besides, the coexistence of magnetic order and Kondo effect is not observable.
Bastide, Christophe. "Etude de quelques problèmes théoriques dans les phases normales et supraconductrices des fermions lourds". Grenoble 1, 1987. http://www.theses.fr/1987GRE10155.
Pełny tekst źródła"ground state of a mixture of two species of fermionic atoms in the one-dimensional optical lattice: a Bosonization study". 2009. http://library.cuhk.edu.hk/record=b5894170.
Pełny tekst źródłaThesis (M.Phil.)--Chinese University of Hong Kong, 2009.
Includes bibliographical references (p. 70-72).
Abstract also in Chinese.
Lu, Wenlong = Yi wei guang ge zi zhong Feimi xing yuan zi hun he wu ji tai xing wei de Bose hua yan jiu / Lu Wenlong.
Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Cold-atom systems --- p.1
Chapter 1.1.1 --- Optical lattices --- p.2
Chapter 1.1.2 --- Feshbach resonance --- p.3
Chapter 1.2 --- Outline of the thesis --- p.6
Chapter 2 --- Bosonization method --- p.8
Chapter 2.1 --- Special property of one-dimensional Fermion system --- p.9
Chapter 2.2 --- Bosonization techniques --- p.13
Chapter 2.2.1 --- Density operators as bosonic fields --- p.14
Chapter 2.2.2 --- Bosonization Identities --- p.17
Chapter 2.3 --- Renormalization analysis for Sine-Gordon field --- p.19
Chapter 2.4 --- Summary --- p.25
Chapter 3 --- Mass imbalance in the spin polarized fermion system --- p.26
Chapter 3.1 --- Kinetic term --- p.29
Chapter 3.2 --- Interaction term --- p.32
Chapter 3.3 --- Phase separation --- p.38
Chapter 3.4 --- Dominant order and pairing behavior --- p.47
Chapter 3.5 --- Summary --- p.49
Chapter 4 --- Mass imbalance in the strong repulsive interaction region --- p.50
Chapter 4.1 --- Effective Hamiltonian at large U limit --- p.50
Chapter 4.2 --- Bosonization of t-J-Jz model --- p.54
Chapter 4.3 --- Phase separation --- p.60
Chapter 4.4 --- Summary --- p.67
Chapter 5 --- Conclusions --- p.68
Bibliography --- p.70
Chapter A --- Proofs of Bosonization --- p.73
Chapter A.1 --- Anti-commutation relations between two branches of fermionic field operators --- p.73
Chapter A.2 --- Bosonization-identities checking --- p.74
Chapter B --- Diagonalization of Quadratic Hamiltonian with Two Bosonic Fields --- p.77
Chapter C --- Correlation functions --- p.82
Chatterjee, Sandeep. "Model Studies Of The Hot And Dense Strongly Interacting Matter". Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2518.
Pełny tekst źródłaChatterjee, Sandeep. "Model Studies Of The Hot And Dense Strongly Interacting Matter". Thesis, 2012. http://etd.iisc.ernet.in/handle/2005/2518.
Pełny tekst źródłaPrasad, Yogeshwar. "Studies of "clean" and "disordered" Bilayer Optical Lattice Systems Circumventing the 'fermionic Cooling-problem'". Thesis, 2018. http://etd.iisc.ac.in/handle/2005/4030.
Pełny tekst źródłaPrasad, Yogeshwar. "Studies of "clean" and "disordered" Bilayer Optical Lattice Systems Circumventing the 'fermionic Cooling-problem'". Thesis, 2018. http://etd.iisc.ernet.in/2005/4003.
Pełny tekst źródłaBodensiek, Oliver. "Superconductivity and Antiferromagnetism in the Kondo-Lattice Model". Doctoral thesis, 2013. http://hdl.handle.net/11858/00-1735-0000-0001-BBE3-3.
Pełny tekst źródłaGuo, Duo. "Fermion Low Modes in Lattice QCD: Topology, the η' Mass and Algorithm Development". Thesis, 2021. https://doi.org/10.7916/d8-knph-2598.
Pełny tekst źródłaSkolimowski, Jan. "Theoretical investigation of correlated fermions on optical lattice with spin-dependent disorder". Doctoral thesis, 2017. https://depotuw.ceon.pl/handle/item/2477.
Pełny tekst źródłaPlaum, Wätzold [Verfasser]. "Numerical analysis using generalised pattern search for a discrete fermionic lattice model of the vacuum / vorgelegt von Wätzold Plaum". 2009. http://d-nb.info/100196330X/34.
Pełny tekst źródłaO'Brien, Aroon. "Charge degrees of freedom on the kagome lattice". Doctoral thesis, 2010. https://monarch.qucosa.de/id/qucosa%3A19565.
Pełny tekst źródłaLenz, Benjamin. "Unconventional Phases in Two-Dimensional Hubbard and Kondo-Lattice Models by Variational Cluster Approaches". Doctoral thesis, 2016. http://hdl.handle.net/11858/00-1735-0000-0023-3DFC-1.
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