arXiv subjects

Pavol Farkasovsky

Publications and source records attributed to Pavol Farkasovsky.

25 records · Page 2Linked to original sources

arXiv2003

Ferromagnetism in the Hubbard model with long-range and correlated hopping

The extrapolation of small-cluster exact-diagonalization calculations is used to examine ferromagnetism in the one-dimensional Hubbard model with long-range and correlated hopping. It is found that the correlated hopping term stabilizes the ferromagnetic state for a wide range of electron interactions $U$ and electron concentrations $n$. The critical value of the interaction strength $U_c$ above which the ferromagnetic state becomes stable is calculated numerically and the ground-state phase diagram of the model is presented for physically the most interesting cases.

cond-mat.str-el↗

arXiv2003

Momentum distribution of itinerant electrons in the one-dimensional Falicov-Kimball model

The momentum distribution $n_k$ of itinerant electrons in the one-dimensional Falicov-Kimball model is calculated for various ground-state phases. In particular, we examine the periodic phases with period two, three and four (that are ground-states for all Coulomb interactions) as well as the phase separated states (that are ground states for small Coulomb interactions). For all periodic phases examined the momentum distribution is a smooth function of $k$ with no sign of any discontinuity or singular behavior at the Fermi surface $k=k_F$. An unusual behavior of $n_k$ (a local maximum) is found at $k=3k_F$ for electron concentrations outside half-filling. For the phase separated ground states the momentum distribution $n_k$ exhibits discontinuity at $k=k_0 < k_F$. This behavior is interpreted in terms of a Fermi liquid.

cond-mat.str-el↗

arXiv2003

Phase transitions induced by correlated hopping in the Falicov-Kimball model

The extrapolation of finite-cluster calculations is used to examine properties of the one-dimensional Falicov-Kimball model with correla It is shown that the correlated hopping strongly influences both the transitions and the conducting properties of the model and so it sho neglected in the correct description of materials with correlated el This is illustrated for two selected values of the Coulomb interacti that represent typical behavior of the model for small and intermedi (strong) interactions. In both cases the insulator-metal transitions (accompanied by continuous or discontinuous valence transitions) ind correlated hopping are observed.

cond-mat.str-el↗

arXiv2003

The spectral properties of the Falicov-Kimball model in the weak-coupling limit

The $f$ and $d$ electron density of states of the one-dimensional Falicov-Kimball model are studied in the weak-coupling limit by exact diagonalization calculations. The resultant behaviors are used to examine the $d$-electron gap ($Δ_{d}$), the $f$-electron gap ($Δ_{f}$), and the $fd$-electron gap ($Δ_{fd}$) as functions of the $f$-level energy $E_f$ and hybridization $V$. It is shown that the spinless Falicov-Kimball model behaves fully differently for zero and finite hybridization between $f$ and $d$ states. At zero hybridization the energy gaps do not coincide ($Δ_{d}\neq Δ_{f} \neq Δ_{fd}$), and the activation gap $Δ_{fd}$ vanishes discontinuously at some critical value of the $f$-level energy $E_{fc}$. On the other hand, at finite hybridization all energy gaps coincide and vanish continuously at the insulator-metal transition point $E_f=E_{fc}$. The importance of these results for a description of real materials is discussed.

cond-mat.str-el↗

arXiv2002

Ferromagnetism in the Hubbard model with a generalized type of hopping

The extrapolation of small-cluster exact-diagonalization calculations is used to examine ferromagnetism in the one-dimensional Hubbard model with a generalized type of hopping. It is found that the long-range hopping with power decaying hopping amplitudes ($t_{ij}\sim q^{|i-j|}$) stabilizes the ferromagnetic state for a wide range of electron interactions $U$ and electron concentrations $n$. The critical value of the interaction strength $U_c(q)$ above which the ferromagnetic state becomes stable is calculated numerically and the ground-state phase diagram of the model (in the $U$-$q$ plane) is presented for physically the most interesting cases.

cond-mat.str-el↗

arXiv2001

Falicov-Kimball model and the problem of electronic ferroelectricity

The density matrix renormalization group method is used to examine possibilities of electronic ferroelectricity in the spinless Falicov-Kimball model. The model is studied for a wide range of parameters including weak and strong interactions as well as the symmetric and unsymmetric case. In all examined cases the $ $-expectation value vanishes for vanishing hybridization $V$, indicating that the spinless Falicov-Kimball model does not allow for a ferroelectric ground state with a spontaneous polarization.

cond-mat.str-el↗

arXiv2001

Ground-state properties of the Falicov-Kimball model with correlated hopping in two dimensions

A new numerical method, recently developed to study ground states of the Falicov-Kimball model (FKM), is used to examine the effects of correlated hopping on the ground-state properties of this model in two dimensions. It is shown that the ground-state phase diagram as well as the picture of metal-insulator transitions found for the conventional FKM (without correlated hopping) are strongly changed when the correlated hopping term is added. The effect of correlated hopping is so strong that it can induce the insulator-metal transition, even in the strong-coupling limit, where the ground states of the conventional FKM are insulating for all $f$-electron densities.

cond-mat.str-el↗