摘要 :
In this paper we propose an exactly solvable model of a topological insulator defined on a spin-1/2 square decorated lattice. Itinerant fermions defined in the framework of the Haldane model interact via the Kitaev interaction wit...
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In this paper we propose an exactly solvable model of a topological insulator defined on a spin-1/2 square decorated lattice. Itinerant fermions defined in the framework of the Haldane model interact via the Kitaev interaction with spin-1/2 Kitaev sublattice. The presented model, whose ground state is a non-trivial topological phase, is solved exactly. We have found out that various phase transitions without gap closing at the topological phase transition point outline the separate states with different topological numbers. We provide a detailed analysis of the model's ground-state phase diagram and demonstrate how quantum phase transitions between topological states arise. We have found that the states with both the same and different topological numbers are all separated by the quantum phase transition without gap closing. The transition between topological phases is accompanied by a rearrangement of the spin subsystem's spectrum from band to flat-band states
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We study a spin- 1/2 chain with six sites per unit cell, in which four spins are located at the vertices of a tetragon and two spins within the center of the cell. There is exchange interaction along links. The model presented has...
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We study a spin- 1/2 chain with six sites per unit cell, in which four spins are located at the vertices of a tetragon and two spins within the center of the cell. There is exchange interaction along links. The model presented has an exact solution for arbitrary values of the exchange integrals and the absence of an external magnetic field. There are two types of local conserved operators for spins in each unit cell. The ground-state phase diagram consists of two topological states with different static uniform Z_2 gauge fields. The Majorana fermions propagate in the background of these fields. In the ground-state flat-band and band, states of the Majorana fermions exist in the chain with different uniform flux sectors. We find that at a critical value of an external magnetic field a phase transition between topological states occurs, accompanied by a fundamental rearrangement of the spectrum. We also provide a detailed analysis of the zero-temperature phase diagram of the model, and demonstrate how this unusual coincidence of a phase transition with a spectrum rearrangement arises.
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A two parametric family of the models of two coupled nondegenerate fermion chains is proposed and solved by the means of the Bethe ansatz. We give a detailed analysis of the exact zero-temperature phase diagram at half filling for...
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A two parametric family of the models of two coupled nondegenerate fermion chains is proposed and solved by the means of the Bethe ansatz. We give a detailed analysis of the exact zero-temperature phase diagram at half filling for different parameters of the interactions. It is shown that insulator and "interchain ferromagnetic" phase states are separated by "intermediate metallic" state, these phase states coexist in a tricritical point. The critical fluctuations are described by a conformal field theory with the central charge c=1. In the tricritical point the fermion state is described as a Luttinger liquid state with one gapless mode that is characterized by abnormal large density-density correlations and correlations of the momentum distribution function.
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A two-band fermion model with boundary fields describing the band structure of a single-walled carbon nanotube (SWNT) is proposed and solved exactly by the nested Bethe ansatz. The fermions, occupying two degenerate subbands that ...
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A two-band fermion model with boundary fields describing the band structure of a single-walled carbon nanotube (SWNT) is proposed and solved exactly by the nested Bethe ansatz. The fermions, occupying two degenerate subbands that are shifted relative to each other, interact via inner- and interband on-site Coulomb interactions, and one-particle and correlated on-site hybridizations. The critical exponents of the correlation functions are calculated using the Bethe ansatz solution and conformal field theory. It is found that a two-component electron liquid state, one of which is defined by an attractive effective electron-electron interaction, is realized for strong hybridized interaction. The attractive interaction leads to the formation of a spinless bound state of Cooper-type pairs and dominating correlations of singlet pairs for arbitrary band fillings. We suggest that this electron pairing mechanism may be the key to resolving the nature of superconductivity in SWNT's.
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The supersymmetric t-J model with boundary hopping integrals and fields is proposed and solved exactly by means of the Bethe ansatz method. We find that for certain values of the boundary hopping integrals and fields the ground st...
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The supersymmetric t-J model with boundary hopping integrals and fields is proposed and solved exactly by means of the Bethe ansatz method. We find that for certain values of the boundary hopping integrals and fields the ground state contains boundary bound states, as new solutions of the Bethe ansatz equations in a charge sector called boundary charge strings. The boundary states define the thermodynamic properties of the boundary, such as the boundary charge, magnetic moment, that have been calculated numerically as a function of the magnetic field and chemical potential. We show that the boundary charge strings lead to a logarithmic divergent behavior of boundary magnetic moment in a weak magnetic field limit.
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摘要 :Highlights?Proposed a new approach for description of phase transitions in topological insulators.?Considered the mechanism of spontaneous breaking of time-reversal symmetry in topological insulators.?The Haldane mo...
展开Highlights?Proposed a new approach for description of phase transitions in topological insulators.?Considered the mechanism of spontaneous breaking of time-reversal symmetry in topological insulators.?The Haldane model can be implemented in real compounds of the condensed matter physics.AbstractThe system of spinless fermions on a hexagonal lattice is studied. We have considered tight-binding model with the hopping integrals between the nearest-neighbor and next-nearest-neighbor lattice sites, that depend on the direction of the link. The links are divided on three types depending on the direction, the hopping integrals are defined by different phases along the links. The energy of th
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The electronic transport properties of single-walled nanotubes (SWNTs) are characterized by the critical exponent Θ, describing the behavior of the single-particle spectral function near the Fermi energy as ρ(ω) ∝ |ω|~Θ. Exp...
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The electronic transport properties of single-walled nanotubes (SWNTs) are characterized by the critical exponent Θ, describing the behavior of the single-particle spectral function near the Fermi energy as ρ(ω) ∝ |ω|~Θ. Experimentally obtained Θ values have been reported in the range of 0.43-0.48 for metallic SWNTs. However, these values are much larger than the theoretical upper limit of the exponent, Θ_(max)=1/8, for the Hubbard model. Here, we show that the observed electronic transport properties can be explained by taking into account a specific hard-core Coulomb interaction. For a many-body system with a hard-core potential, we analytically calculate the critical exponents using the Bethe ansatz and conformal field theory. We find strongly interacting Luttinger liquid states that are characterized by large Θ values, consistent with the empirical results, suggesting that these states are actually realized in metallic SWNTs and organic conductors.
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The two-band model describing strongly hybridized degenerated electron states in a chain is proposed and solved exactly by means of the Bethe ansatz. The fermions of the subbands interact with each other via one-particle and one-p...
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The two-band model describing strongly hybridized degenerated electron states in a chain is proposed and solved exactly by means of the Bethe ansatz. The fermions of the subbands interact with each other via one-particle and one-particle correlated on-site hybridized interactions. The chain of electrons is reduced to the model with two noninteracting subbands with a given total number of electrons, in which fermions interact via different effective constants of interactions. In the case of strong hybridized interaction the on-site repulsive interaction is compensated by hybridized interaction, which leads to an effective attractive interaction between particles and the formation of spinless bound states of Cooper type. This electron liquid component determines both heavy fermion- and superconducting-type behavior of electron properties.
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