Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 35 for “"Triangular lattice"”.
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Strongly Correlated Electrons on a Triangular Lattice
In this thesis we are going to study the properties of strongly correlated electron systems (SCES) using analytical, phenomenological and computational methods. In the introductory chapter we will discuss generally the problem of strongly correlated electron systems and the methods that are used to …
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Bose-Hubbard physics in the kagome and triangular optical lattices at negative absolute temperature
… with ultracold bosonic ³⁹K in the kagome and triangular optical lattices. These lattices display geometric frustration, which manifests itself in a degeneracy at the upper edge of the ground band manifold. In the case of the triangular lattice, the band structure features two inequivalent …
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Nonreciprocal phenomena in superconductivity
… insulators in a magnetic field, described by a triangular-lattice Fermi-Hubbard model in the limit of strong interaction. This is relevant for many novel materials, such as moiré transition metal dichalcogenides bilayers. We predict a new bound state, spin polaron, formed by binding a doped hole …
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Magnetic properties of transition metal dichloride - graphite intercalation compounds
… a two-dimensional easy-plane ferromagnet on a triangular lattice. It is found to order in two iv steps, the higher-temperature phase showing no three-dimensional static correlations, and the lower phase exhibiting a weak antiferromagnetic correlation between neighboring intercalate layers . We …
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Negative temperature states of bosons in triangular and kagome lattices
… to study quantum many-body states in frustrated lattices. For the first time, we load the atoms into the optical triangular and kagome lattices at negative temperature, where most atoms occupy the states with the highest energy. Due to geometric frustration, the highest energy states are Bloch …
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Quantum simulations on square and triangular Hubbard models
… can be modeled by a two-dimensional square- and triangular-lattice Hubbard model respectively. The formation of the superconducting dome requires explanations of feasible scenarios. Generally speaking, pairing strength is provided by magnetic fl_x001D_uctuations in the strongly correlated region …
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Studies of protein designability using reduced models
… In particular, the 2D square and the 3D cubic lattices together with reduced amino acid alphabets have been examined extensively and have lead to interesting results that shed some light on evolutionary relationship among proteins. Here, additionally to the 2D square lattice, we study the 2D …
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The Q-closeness technique: an application to isoperimetric inequalities in 2-d lattices and to the Faber-Krahn inequality
… of two variational problems on periodic lattices, by exploiting the Q-closeness technique introduced by Cicalese and Leonardi, which enables us to lift discrete problems into the the continuous framework by associating suitable domains to configurations of points. In particular, in the …
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Design of a photonic crystal planar Luneburg lens for optical beam steering
… consisting of amorphous silicon patterned with a triangular lattice of holes layered on top of silicon nitride. Multiple waveguides can be placed along the focal circle of the lens and the lens is designed to collimate the beam from the waveguides. Through full-wave simulations, the lens is shown …
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Optical and core-level X-ray spectroscopy of correlated two-dimensional materials
… vdW materials. We first investigate the triangular lattice antiferromagnet NiI₂. Frustrated exchange interactions result in a helimagnetic ground state and spin-induced ferroelectric order, making bulk NiI₂ a type-II multiferroic. Using a combination of optical spectroscopic probes, …
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An inverted hydride-fueled pressurized water reactor concept
… oriented, cooling channels, arranged in a triangular lattice. A pin vs inverted comparison, performed at cell level, shows that an inverted geometry can attain the same fuel volume fraction of the pin geometry but with a much lower pressure drop and fuel temperature. Also, CHF performance …
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Transport in nanoscale systems
… the dots onto the frustrated spin model on the triangular lattice. A number of phases is identified for this system. Phase diagram is studied by means of the height field order parameter. Novel correlated fluid phase is identified, in which transport of classical charges exhibits correlated …
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Enhanced performance of optical sources in III-V materials using photonic crystals
… nonradiative surface recombination pathways, a triangular lattice photonic crystal in two-dimensions is etched into the top layer of an asymmetric InGaP/InGaAs quantum well structure emitting at 980 nm. Enhanced injection and external efficiency of the LED is demonstrated. Chapter 3 develops …
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Quantum simulation with an optical kagome lattice
… based quantum simulator for studying the kagome lattice and the associated flat band. Despite a copious amount of theoretical effort to elucidate the physics of the kagome lattice, experimental kagome physics is still in its infancy. In the case of ultracold atoms, this is mainly due to …
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A numerical assessment of architectural parameters for anisotropic behavior in idealised trabecular structures
… a complex, heterogeneous, anisotropic open cell lattice structure with a large variation in mechanical properties across anatomic site, species, sex, age, normal loading direction and disease state. A common attempt to account for this variation is to correlate the structure of the trabecular …
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Phase Stabilised Superlattices for Quantum Simulation
… in the future fermionic) atoms in interesting triangular superlattice structures. We show that this machine can reliably and stably produce samples of ultracold potassium and rubidium in the lowest band of the kagome lattice. We discuss the characterisation and validation of the apparatus as …
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A Study of Narrowband Noise Characteristics Associated with Vortex Motion in High Temperature Superconductors
… vortex densities, while for higher densities a triangular lattice is obtained along with a washboard signal and higher harmonics. For point defects a washboard signal with higher harmonics is always observed in the region investigated. These results suggest that power spectra for both point and …
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Exotic phenomena in rare-earth based geometrically frustrated magnets
… pyrochlore oxides (RE2TM2O7) and a 2D isosceles triangular lattice material K3Er(VO4)2. Spin-1/2 antiferromagnetic (AFM) 2D triangular lattice magnets are an archetype of geometric frustration. While these materials are theorized to host a variety of different ground states and exotic phases …
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On numerical methods in quantum spin systems
… of an extended Heisenberg model on a kagome lattice. Chapter 6 studies a quantum Heisenberg model on the stuffed honeycomb lattice. Phase transitions in quantum many body systems manifest themselves as a reorganization of low energy spectra of the system. They come in a variety of forms …
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Observing the 2D Bose glass in an optical quasicrystal
… a two-dimensional (2D) quasicrystalline optical lattice for ultracold atoms and conduct matter-wave diffraction experiment using shot, intense lattice pulses. We reveal the different diffraction dynamics between periodic and quasiperiodic lattices and demonstrate the capability to simulate …
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