Thermodynamic studies of the two dimensional Falicov-Kimball model on a triangular lattice (original) (raw)
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Phase transitions in a spinless, extended Falicov–Kimball model on the triangular lattice
Solid State Communications, 2013
A numerical diagonalization technique with canonical Monte-Carlo simulation algorithm is used to study the phase transitions from low temperature (ordered) phase to high temperature (disordered) phase of spinless Falicov-Kimball model on a triangular lattice with correlated hopping (t ′). It is observed that the low temperature ordered phases (i.e. regular, bounded and segregated) persist up to a finite critical temperature (T c). In addition, we observe that the critical temperature decreases with increasing the correlated hopping in regular and bounded phases whereas it increases in the segregated phase. Single and multi peak patterns seen in the temperature dependence of specific heat (C v) and charge susceptibility (χ) for different values of parameters like on-site Coulomb correlation strength (U), correlated hopping (t ′) and filling of localized electrons (n f) are also discussed.
Study of ground state phases for spin-1/2 Falicov–Kimball model on a triangular lattice
Solid State Communications, 2014
The spin-dependent Falicov-Kimball model (FKM) is studied on a triangular lattice using numerical diagonalization technique and Monte-Carlo simulation algorithm. Magnetic properties have been explored for different values of parameters: on-site Coulomb correlation U, exchange interaction J and filling of electrons. We have found that the ground state configurations exhibit long range Neèl order, ferromagnetism or a mixture of both as J is varied. The magnetic moments of itinerant (d) and localized (f) electrons are also studied. For the one-fourth filling case we found no magnetic moment from d-and f-electrons for U less than a critical value.
The European Physical Journal B, 2020
Ground state properties of the spin−1/2 Falicov-Kimball model on a triangular lattice in the presence of uniform external magnetic field are explored. Both the orbital and the Zeeman field-induced effects are taken into account and in each unit cell only rational flux fractions are considered. Numerical results, obtained with the help of Monte Carlo simulation algorithm, reveal that the ground state properties strongly depend on the onsite Coulomb correlation between itinerant and localized electrons, orbital magnetic field as well as the Zeeman splitting. Strikingly, for the on-site Coulomb correlation U/t ≈ 1, the Zeeman splitting produces a phase transition from paramagnetic metal/insulator to ferromagnetic insulator/metal transition in the itinerant electron subsystem accompanied by the phase segregation to the bounded/regular phase in the localized electrons subsystem. For the onsite Coulomb correlation U/t ≈ 5, although no metal to insulator transition is observed but a magnetic phase transition from paramagnetic phase to ferromagnetic phase in the itinerant electron subsystem is observed with the Zeeman splitting. These results are applicable to the layered systems e.g. cobaltates, rare earth and transition metal dichalcogenides, GdI 2 , N aT iO 2 , N aV O 2 and Be x Zn 1−x O etc. It has been also proposed that the results can be realized in the optical lattices with mixtures of light atoms and heavy atoms using the cold atomic techniques.
Solid State Communications, 2017
Ground state properties of spinless, extended Falicov-Kimball model (FKM) on a finite size triangular lattice with orbital magnetic field normal to the lattice are studied using numerical diagonalization and Monte-Carlo simulation methods. We show that the ground state configurations of localized electrons strongly depend on the magnetic field. Magnetic field induces a metal to insulator transition accompanied by segregated phase to an ordered regular phase except at density n f = 1/2 of localized electrons. It is proposed that magnetic field can be used as a new tool to produce segregated phase which was otherwise accessible only either with correlated hopping or with large on-site interactions.
Thermodynamic Properties of the Generalized Falicov–Kimball Model
Journal of Superconductivity, 2000
The thermodynamic properties: specific heat and magnetization are studied as a function of temperature, doping, and interlevel spacing within the two-dimensional extended Falicov-Kimball model for spinless fermions. It was recently shown that the strong coupling limit of the above model possesses electronically driven ferroelectric order. Thermodynamic quantities are calculated using the finite-temperature Lanczos method with additional phase-averaging for a system of 4 × 4 sites. Our results indicate that valence transition exists in the extended Falicov-Kimball model.
An extended Falicov-Kimball model on a triangular lattice
EPL (Europhysics Letters), 2011
The combined effect of frustration and correlation in electrons is a matter of considerable interest of late. In this context a Falicov-Kimball model on a triangular lattice with two localized states, relevant for certain correlated systems, is considered. Making use of the local symmetries of the model, our numerical study reveals a number of orbital ordered ground states, tuned by the small changes in parameters while quantum fluctuations between the localized and extended states produce homogeneous mixed valence. The inversion symmetry of the Hamiltonian is broken by most of these ordered states leading to orbitally driven ferroelectricity. We demonstrate that there is no spontaneous symmetry breaking when the ground state is inhomogeneous. The study could be relevant for frustrated systems like GdI2, N aT iO2 (in its low temperature C2/m phase) where two Mott localized states couple to a conduction band.
Thermodynamics of the two-dimensional Falicov-Kimball model: A classical Monte Carlo study
Physical Review B, 2006
The two-dimensional Falicov-Kimball (FK) model is analyzed using Monte Carlo method. In the case of concentrations of both itinerant and localized particles equal to 0.5 we determine temperature dependence of specific heat, charge density wave susceptibility and density-density correlation function. In the weak interaction regime we find a first order transition to the ordered state and anomalous temperature dependence of the correlation function. We construct the phase diagram of half-filled FK model. Also, the role of next-nearest-neighbor hopping on the phase diagram is analyzed. Lastly, we discuss the density of states and the spectral functions for the mobile particles in weak and strong interaction regime.
2015
Ground state magnetic properties are studied by incorporating the super-exchange interaction (J se) in the spindependent Falicov-Kimball model (FKM) between localized (f-) electrons on a triangular lattice for half filled case. Numerical diagonalization and Monte-Carlo simulation are used to study the ground state magnetic properties. We have found that the magnetic moment of (d-) and (f-) electrons strongly depend on the value of Hund's exchange (J), superexchange interaction (J se) and also depends on the number of (d-) electrons (N d). The ground state changes from antiferromagnetic (AFM) to ferromagnetic (FM) state as we decrease (N d). Also the density of d electrons at each site depends on the value of J and J se .
Thermal transport in the Falicov-Kimball model on a Bethe lattice
Physical Review B, 2004
We calculate thermal transport in the Falicov-Kimball model on an infinite-coordination-number Bethe lattice. We perform numerical calculations of the thermoelectric characteristics and concentrate on finding materials parameters for which the electronic thermoelectric figure-of-merit ZT is large, suggesting potential cooling and power generation applications. Surprisingly, the Bethe lattice has significant qualitative and quantitative differences with the previously studied hypercubic lattice. At low temperature it is unlikely that these systems can be employed in thermoelectric devices due to the low conductivities and due to a larger lattice contribution to the thermal conductivity κL, but at high temperature, the thermoelectric parameters appear more promising for devices due to a significant enhancement of ZT and a smaller relative contribution by the lattice thermal conductivity.
Ground-State Energy and Low-Temperature Behavior of the One-Dimensional Falicov-Kimball Model
Europhysics Letters (EPL), 1993
We consider the Falicov-Kimball model in the case of an equal number of classical > and quantum <> with Fermi statistics. In one dimension we find an exact formula for the leading behavior of the ground-state energy as a function of the attractive potential U between electrons and nuclei. For U > U, the system forms <<atoms. which have an effective repulsion between them. Similar results hold for a continuum model provided there is a sufficiently large hard core between the nuclei. Some low-temperature properties are also discussed. We consider the Falicov-Kimball model as a very primitive model of matter which retains two basic features of electrons and nuclei: the two types of constituents attract each other and the .electrons>> are subject to the Pauli principle. The auclei>> are considered as classical particles with a <<hard core),, occupying the sites of a lattice Z d. The electrons and nuclei interact by an attractive on-site potential. The kinetic energy of an electron is given by the lattice Laplacian Kq =-81i-jl, + 2d8ij. For a given configuration of M nuclei the single-electron Hamiltonian has the matrix elements h, = Kq-Unidq, U > 0, ni = 1, 0