arXiv subjects

Lucia Galisova

Publications and source records attributed to Lucia Galisova.

16 recordsLinked to original sources

arXiv2019

Pairwise entanglement in double-tetrahedral chain with different Landé g-factors of the Ising and Heisenberg spins

The pairwise entanglement is exactly examined in the spin-1/2 Ising-Heisenberg double-tetrahedral chain with different Landé g-factors of the Ising and Heisenberg spins at zero and finite temperatures. It is shown that the phenomenon present in quantum non-chiral ground states is twice as strong as in quantum chiral ground states and that it gradually diminishes with increasing temperature until it completely vanishes at a certain threshold temperature. It is also demonstrated that the strong magnetic field maintains a weak thermal entanglement quite far from the saturation field, although the ground state is non-entangled.

cond-mat.stat-mech↗

arXiv2019

Frustration phenomenon in the spin-1/2 Ising-Heisenberg planar model of inter-connected trigonal bipyramid structures

Ground-state and finite-temperature properties of the exactly solvable mixed spin-1/2 Ising-Heisenberg planar model composed of identical trigonal bipyramids that are arranged into a regular archimedean lattice are examined with the aim to clarify the frustration phenomenon at zero and finite temperatures. It is shown that the ground-state spin frustration persists even far above the second-order phase transition. If the interaction ratio between the Heisenberg and Ising exchange interactions is close enough to the ground-state boundaries between the neighboring phases, a remarkable re-entrance of the (non-)frustrated spin arrangement of the Heisenberg spins can be observed around the critical temperature of the model. It is also evidenced that entropy and specific heat show pronounced temperature variations not only around the critical temperature, but also in low-temperature regime if values of the interaction parameters are taken from neighborhood of the ground-state phase transitions, where energies of the neighboring phases are very close.

cond-mat.stat-mech↗

arXiv2018

Macroscopic ground-state degeneracy and magnetocaloric effect in the exactly solvable spin-1/2 Ising-Heisenberg double-tetrahedral chain

The ground-state degeneracy and magnetocaloric effect in the spin-$1/2$ Ising-Heisenberg double-tetrahedral chain are exactly investigated. It is demonstrated that the zero-temperature phase diagram involves two classical and two quantum chiral phases with distinct degrees of the macroscopic degeneracy. Different macroscopic degeneracies observed in the latter phases and at individual ground-state phase transitions are confirmed by multiple-peak dependencies of the specific heat and entropy on the magnetic field. The cooling capability of the model is well illustrated by the magnetic-field variations of the isothermal entropy change, temperature isotherms and the magnetic Grüneisen parameter.

cond-mat.stat-mech↗

arXiv2018

Magnetic and magnetocaloric properties of the exactly solvable mixed-spin Ising model on a decorated triangular lattice in a magnetic field

The ground state, zero-temperature magnetization process, critical behaviour and isothermal entropy change of the mixed-spin Ising model on a decorated triangular lattice in a magnetic field are exactly studied after performing the generalized decoration-iteration mapping transformation. It is shown that both the inverse and conventional magnetocaloric effect can be found near the absolute zero temperature. The former phenomenon can be found in a vicinity of the discontinuous phase transitions and their crossing, while the latter one occurs in some paramagnetic phases due to a spin frustration to be present at zero magnetic field. The inverse magnetocaloric effect can also be detected slightly above continuous phase transitions following the power-law dependence $|-Δ{\cal S}_{iso}^{min}|\propto h^n$, where $n$ depends basically on the ground-state spin ordering.

cond-mat.stat-mech↗

arXiv2017

Magnetization plateau as a result of the uniform and gradual electron doping in a coupled spin-electron double-tetrahedral chain

The double-tetrahedral chain in a longitudinal magnetic field, whose nodal lattice sites occupied by the localized Ising spins regularly alternate with triangular plaquettes with the dynamics described by the Hubbard model, is rigorously investigated. It is demonstrated that the uniform change of electron concentration controlled by the chemical potential in a combination with the competition between model parameters and the external magnetic field leads to the formation of one chiral and seven non-chiral phases at the absolute zero temperature. Rational plateaux at one-third and one-half of the saturation magnetization can also be identified in the low-temperature magnetization curves. On the other hand, the gradual electron doping results in eleven different ground-state regions which distinguish from each other by the evolution of the electron distribution during this process. Several doping-dependent magnetization plateaux are observed in the magnetization process as a result of the continuous change of electron content in the model.

cond-mat.str-el↗

arXiv2017

On the ground-state degeneracy and entropy in a double-tetrahedral chain formed by the localized Ising spins and mobile electrons

Ground-state properties of a hybrid double-tetrahedral chain, in which the localized Ising spins regularly alternate with triangular plaquettes occupied by a variable number of mobile electrons, are exactly investigated. We demonstrate that the zero-temperature phase diagram of the model involves several non-degenerate, two-fold degenerate and macroscopically degenerate chiral phases. Low-temperature dependencies of the entropy and specific heat are also examined in order to gain a deeper insight into the degeneracy of individual ground-state phases and phase transitions. It is shown that a diversity of the ground-state degeneracy manifests itself in multiple-peak structures of both thermodynamic quantities. A remarkable temperature dependencies of the specific heat with two and three Schottky-type maxima are discussed in detail.

cond-mat.str-el↗

arXiv2016

Reentrant phenomenon and inverse magnetocaloric effect in a generalized spin-(1/2,s) Fisher's super-exchange antiferromagnet

The thermodynamic and magnetocaloric properties of a generalized spin-$(1/2,s)$ Fisher's super-exchange antiferromagnet are exactly investigated by using the decoration-iteration mapping transformation. Besides the critical temperature, sublattice magnetization, total magnetization, entropy and specific heat, the isothermal entropy change and adiabatic temperature change are rigorously calculated in order to examine cooling efficiency of the model in a vicinity of the first- and second-order phase transitions. It is shown that an enhanced inverse magnetocaloric effect occurs around the temperature interval $T_c(B\neq 0) \lesssim T < T_c(B = 0)$ for any magnetic-field change $ΔB: 0 \to B$. The most pronounced inverse magnetocaloric effect can be found nearby the critical field, which corresponds to the zero-temperature phase transition from the long-range ordered ground state to the paramagnetic one. The observed phenomenon increases with the increasing value of decorating spins. Furthermore, sufficiently high values of decorating spins have also linked to a possibility of observing reentrant phase transitions at finite temperatures.

cond-mat.stat-mech↗

arXiv2016

Ground-state and magnetocaloric properties of a coupled spin-electron double-tetrahedral chain (exact study at the half filling)

Ground-state and magnetocaloric properties of a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with triangular clusters half filled with mobile electrons, are exactly investigated by using the transfer-matrix method in combination with the construction of the $N$th tensor power of the discrete Fourier transformation. It is shown that the ground state of the model is formed by two non-chiral phases with the zero residual entropy and two chiral phases with the finite residual entropy $S = Nk_{\rm B}\ln 2$. Depending on the character of the exchange interaction between the localized Ising spins and mobile electrons, one or three magnetization plateaus can be observed in the magnetization process. Their heights basically depend on the values of Landé $g$-factors of the Ising spins and mobile electrons. It is also evidenced that the system exhibits both the conventional and inverse magnetocaloric effect depending on values of the applied magnetic field and temperature.

cond-mat.stat-mech↗

arXiv2016

Inverse magnetocaloric effect in the spin-1/2 Fisher's super-exchange antiferromagnet

The isothermal entropy change and the adiabatic temperature change for the exactly solved spin-1/2 Fisher's super-exchange antiferromagnet are rigorously calculated in order to examine magnetocaloric properties of the model in a vicinity of the second-order phase transition. It is shown that the large inverse magnetocaloric effect occurs around the temperature interval $T_c(h\neq0) < T < T_c(h=0)$ for any magnetic-field change $Δh: 0 \to h$. The most pronounced inverse magnetocaloric effect can be found for the magnetic-field change, which coincides with the critical field of a zero-temperature phase transition from the antiferromagnetically ordered ground state to the paramagnetic one.

cond-mat.stat-mech↗

arXiv2015

Thermodynamics of the exactly solvable spin-electron tetrahedral chain

An exactly solvable spin-electron tetrahedral chain, where the Ising spins localized at nodal lattice sites regularly alternate with three equivalent lattice sites available for one mobile electron is considered. The system with ferromagnetic interaction between the Ising spins and electrons exhibits an enhanced magnetocaloric effect (MCE) in the limit $H/|J|\to 0$ when the entropy is very small, whereas the system with antiferromagnetic interaction between the Ising spins and electrons exhibits an enhanced MCE around the field $H/J=1$ when the entropy is sufficiently close to the value $S/2N = \ln[(1+\sqrt{5})/2]$. We study the thermodynamics of the system in these field regions.

cond-mat.stat-mech↗

arXiv2015

Magnetic Gruneisen parameter and magnetocaloric properties of a coupled spin-electron double-tetrahedral chain

Magnetocaloric effect in a double-tetrahedral chain, in which nodal lattice sites occupied by the localized Ising spins regularly alternate with three equivalent lattice sites available for mobile electrons, is exactly investigated by considering the one-third electron filling and the ferromagnetic Ising exchange interaction between the mobile electrons and their nearest Ising neighbours. The entropy and the magnetic Gruneisen parameter, which closely relate to the magnetocaloric effect, are exactly calculated in order to investigate the relation between the ground-state degeneracy and the cooling efficiency of the hybrid spin-electron system during the adiabatic demagnetization.

cond-mat.stat-mech↗

arXiv2015

Magnetocaloric effect in the symmetric spin-1/2 diamond chain with different Landé g-factors of Ising and Heisenberg spins

The symmetric spin-1/2 Ising-Heisenberg diamond chain with different Landé g-factors of Ising and Heisenberg spins is exactly solved by combining the generalized decoration-iteration transformation and transfer-matrix method. The ground state of the system and magnetocaloric effect during the adiabatic (de)magnetization are particularly examined. It is evidenced that the considered mixed-spin diamond chain exhibits an enhanced magnetocaloric effect during the adiabatic (de)magnetization in the vicinity of field-induced phase transitions as well as in the zero-field limit if the frustrated phase constitutes the zero-field ground state, but the cooling efficiency depends on whether the system is macroscopically degenerate in these parameter regions or not.

cond-mat.stat-mech↗

arXiv2015

Vigorous thermal excitations in a double-tetrahedral chain of localized Ising spins and mobile electrons mimic a temperature-driven first-order phase transition

A hybrid spin-electron system defined on one-dimensional double-tetrahedral chain, in which the localized Ising spin regularly alternates with two mobile electrons delocalized over a triangular plaquette, is exactly solved with the help of generalized decoration-iteration transformation. It is shown that a macroscopic degeneracy of ferromagnetic and ferrimagnetic ground states arising from chiral degrees of freedom of the mobile electrons cannot be lifted by a magnetic field in contrast to a macroscopic degeneracy of the frustrated ground state, which appears owing to a kinetically-driven frustration of the localized Ising spins. An anomalous behavior of all basic thermodynamic quantities can be observed on account of massive thermal excitations, which mimic a temperature-driven first-order phase transition from the non-degenerate frustrated state to the highly degenerate ferrimagnetic state at non-zero magnetic fields. A substantial difference in the respective degeneracies is responsible for an immense low-temperature peak of the specific heat and very abrupt (almost discontinuous) thermal variations of the entropy and sublattice magnetizations.

cond-mat.stat-mech↗

arXiv2012

On the compressibility of deformable spin chains in a vicinity of quantum critical points

We calculate the ground-state compressibility of a deformable spin-1/2 Heisenberg-Ising chain with Dzyaloshinskii-Moriya interaction to discuss how a quantum critical point inherent in this spin system may manifest itself in the elastic properties of the underlying lattice. We compare these results with the corresponding ones for the spin-1/2 Ising chain in a longitudinal or transverse field and the spin-1/2 $XX$ chain in a transverse field. The inverse compressibility of the spin-1/2 $XX$ chain in a transverse field exhibits a hysteresis in a vicinity of quantum critical point that is accompanied with the finite jump of compressibility. Contrary to this, the inverse compressibility diminishes continuously close to a quantum critical point of the spin-1/2 Ising chain in a transverse field and the spin-1/2 Heisenberg-Ising bond alternating chain.

cond-mat.str-el↗

arXiv2012

Magnetic properties of the spin-1/2 Ising-Heisenberg diamond chain with the four-spin interaction

A symmetric spin-1/2 Ising-Heisenberg diamond chain with the Ising four-spin interaction is exactly solved by means of the generalized decoration-iteration mapping transformation. The ground state, the magnetization process and thermodynamics are particularly examined for the case of antiferromagnetic pair interactions (Ising and isotropic Heisenberg ones). It is shown that an interplay between pair interactions, the four-spin interaction and the external magnetic field gives rise to several quantum ground states with entangled spin states in addition to some semi-classically ordered ones. Besides, the temperature dependence of the magnetic susceptibility multiplied by the temperature is studied and the interesting triple-peak specific heat curve is also detected when considering the zero-field region rather close to the triple point, where three different ground states coexist.

cond-mat.stat-mech↗

arXiv2010

Effect of on-site Coulomb repulsion on phase transitions in exactly solved spin-electron model

A hybrid lattice-statistical model on doubly decorated planar lattices, which have localized Ising spins at their nodal lattice sites and two itinerant electrons at each pair of decorating sites, is exactly solved by the use of a generalized decoration-iteration transformation. Our main attention is focused on an in uence of the on-site Coulomb repulsion on ground-state properties and critical behavior of the investigated system.

cond-mat.stat-mech↗