Search results for "Phase Transition"
showing 10 items of 1281 documents
The Topological Phase Transitions Related to Fermion Condensate
2014
In this chapter, we consider so-called topological phase transitions, taking place in normal Fermi liquid. In other words, here we are dealing with different instabilities of normal Fermi liquids relative to several kinds of perturbations of initial quasiparticle spectrum \(\varepsilon (p)\) and occupation numbers \(n(p)\) associated with the emergence of a multi-connected Fermi surface. Depending on the parameters and analytical properties of the Landau interaction, such instabilities lead to several possible types of restructuring of initial Landau Fermi liquid ground state. This restructuring generates topologically distinct phases. One of them is the FC discussed above, another one belo…
Vibrational properties of delafossiteCuGaO2at ambient and high pressures
2005
In this paper we investigate the vibrational properties of $\mathrm{Cu}\mathrm{Ga}{\mathrm{O}}_{2}$ delafossite by means of Raman experiments and ab initio calculations. Both investigations have been performed at ambient pressure and also at high pressure. The two Raman-active modes have frequencies ${w}_{{E}_{g}}=368\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and ${w}_{{A}_{1g}}=729\ifmmode\pm\else\textpm\fi{}1\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$, and pressure coefficients $2.78\ifmmode\pm\else\textpm\fi{}0.03\phantom{\rule{0.3em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}∕\mathrm{GPa}$ $({E}_{g})$ and $4.64\ifmmode\pm\else\text…
Ab initiostudy of compressedAr(H2)2: Structural stability and anomalous melting
2010
We study the structural stability and dynamical properties of $\text{Ar}{({\text{H}}_{2})}_{2}$ under pressure using first-principles and ab initio molecular-dynamics techniques. At low temperatures, $\text{Ar}{({\text{H}}_{2})}_{2}$ is found to stabilize in the cubic C15 Laves structure $({\text{MgCu}}_{2})$ and not in the hexagonal C14 Laves structure $({\text{MgZn}}_{2})$ as it has been assumed previously. Based on enthalpy energy and phonon calculations, we propose a temperature-induced ${\text{MgCu}}_{2}\ensuremath{\rightarrow}{\text{MgZn}}_{2}$ phase transition that may rationalize the existing discrepancies between the sets of Raman and infrared vibron measurements. Our AIMD simulati…
Exciton Gas Compression and Metallic Condensation in a Single Semiconductor Quantum Wire
2008
4 páginas, 5 figuras.-- PACS numbers: 78.67.Lt, 71.30.+h, 71.35. -y.-- Comunicación presentada a la International Conference on the Physics of Semiconductors (ICPS) celebrada en Rio de Jqaneiro (Brasil/2008).
Three dimensional hydrodynamics of ultrarelativistic heavy ion collisions
1988
We have utilized a 2+1 dimensional numerical code based on Flux Corrected Transport method to find a solution for 3+1 dimensional cylindrically symmetric hydrodynamic flow of hadronic matter which is assumed to be formed in extremely high energy heavy ion collisions. The hydrodynamics is supplemented with a decoupling calculation in order to produce measurable particle distributions. This numerical procedure is applied here to Landau type initial conditions which have been fixed using a simple geometrical picture for a central O+Pb collision at 200 GeV/nucleon. The bag equation of state for nonbaryonic matter is used to simulate the deconfinement phase transition to quark gluon plasma. The …
Noncritical generation of nonclassical frequency combs via spontaneous rotational symmetry breaking
2016
Synchronously pumped optical parametric oscillators (SPOPOs) are optical cavities containing a nonlinear crystal capable of down-converting a frequency comb to lower frequencies. These have received a lot of attention lately, because their intrinsic multimode nature makes them compact sources of quantum correlated light with promising applications in modern quantum information technologies. In this work we show that SPOPOs are also capable of accessing the challenging but interesting regime where spontaneous symmetry breaking plays a crucial role in the quantum properties of the emitted light, difficult to access with any other nonlinear optical cavity. Apart from opening the possibility of…
Renormalization group flows for Wilson-Hubbard matter and the topological Hamiltonian
2019
Understanding the robustness of topological phases of matter in the presence of interactions poses a difficult challenge in modern condensed matter, showing interesting connections to high energy physics. In this work, we leverage these connections to present a complete analysis of the continuum long-wavelength description of a generic class of correlated topological insulators: Wilson-Hubbard topological matter. We show that a Wilsonian renormalization group (RG) approach, combined with the so-called topological Hamiltonian, provide a quantitative route to understand interaction-induced topological phase transitions that occur in Wilson-Hubbard matter. We benchmark two-loop RG predictions …
First Versus Second Order Phase Transitions in the Three-Dimensional Three-State Potts Model in Random Fields
1995
The ordering of three-states Potts ferromagnets on the simple cubic lattice exposed to random fields is investigated by extensive Monte Carlo simulations. Evidence is presented that the transition is second order for intermediate strength of the fields, while it presumably is first order for large field strength. The implications for various theoretical predictions are briefly discussed.
Theory of orientational glasses models, concepts, simulations
1992
Abstract This review describes the various attempts to develop a theoretical understanding for ordering and dynamics of randomly diluted molecular crystals, where quadrupole moments freeze in random orientations upon lowering the temperature, as a result of randomness and competing interactions. While some theories attempt to model this freezing into a phase with randomly oriented quadrupole moments in terms of a bond-disorder concept analogous to the Edwards-Anderson model of spin glasses, other theories attribute the freezing to random field-like terms in the Hamiltonian. While models of the latter type have been studied primarily by microscopic molecular field-type treatments, the former…
Magnetic field and temperature dependent correlations in the singlet ground state system CsFeBr3
1992
Abstract In the singlet ground state system CsFeBr 3 the temperature and magnetic field dependence of the magnetic dispersion curves have been measured by inelastic neutron scattering. At a field of 4.1 T magnetic Bragg peaks appear at (⅓ ⅓ 1) and (⅔ ⅔ 1). The correlation lengths were derived from the experimental data by integrating the constant Q -scans over the energy transfer. The Q -dependence was fitted to Lorentzians and correlations lengths were extracted for different directions in the lattice. These correlation lengths decrease with increasing temperature and increase with increasing field. Above the phase transition the correlation lengths decrease again.