355 research outputs found
Quantum Correlation in One-dimensional Extend Quantum Compass Model
We study the correlations in the one-dimensional extended quantum compass
model in a transverse magnetic field. By exactly solving the Hamiltonian, we
find that the quantum correlation of the ground state of one-dimensional
quantum compass model is vanishing. We show that quantum discord can not only
locate the quantum critical points, but also discern the orders of phase
transitions. Furthermore, entanglement quantified by concurrence is also
compared.Comment: 8 pages, 14 figures, to appear in Eur. Phys. J.
Thermodynamic Properties of the One-Dimensional Extended Quantum Compass Model in the Presence of a Transverse Field
The presence of a quantum critical point can significantly affect the
thermodynamic properties of a material at finite temperatures. This is
reflected, e.g., in the entropy landscape S(T; c) in the vicinity of a quantum
critical point, yielding particularly strong variations for varying the tuning
parameter c such as magnetic field. In this work we have studied the
thermodynamic properties of the quantum compass model in the presence of a
transverse field. The specific heat, entropy and cooling rate under an
adiabatic demagnetization process have been calculated. During an adiabatic
(de)magnetization process temperature drops in the vicinity of a field-induced
zero-temperature quantum phase transitions. However close to field-induced
quantum phase transitions we observe a large magnetocaloric effect
Emergent phases in a compass chain with multisite interactions
We study a dimerised spin chain with biaxial magnetic interacting ions in the
presence of an externally induced three-site interactions out of equilibrium.
In the general case, the three-site interactions play a role in renormalizing
the effective uniform magnetic field. We find that the existence of zero-energy
Majorana modes is intricately related to the sign of Pfaffian of the
Bogoliubov-de Gennes Hamiltonian and the relevant topological invariant.
In contrast, we show that an exotic spin liquid phase can emerge in the compass
limit through a Berezinskii-Kosterlitz-Thouless (BKT) quantum phase transition.
Such a BKT transition is characterized by a large dynamic exponent , and
the spin-liquid phase is robust under a uniform magnetic field. We find the
relative entropy and the quantum discord can signal the BKT transitions. We
also uncover a few differences in deriving the correlation functions for the
systems with broken reflection symmetry.Comment: 12 pages, 10 figure
Ordered states in the Kitaev-Heisenberg model: From 1D chains to 2D honeycomb
We study the ground state of the 1D Kitaev-Heisenberg (KH) model using the
density-matrix renormalization group and Lanczos exact diagonalization methods.
We obtain a rich ground-state phase diagram as a function of the ratio between
Heisenberg ( and Kitaev () interactions. Depending on
the ratio, the system exhibits four long-range ordered states:
ferromagnetic- , ferromagnetic-, staggered-, N\'eel-, and two
liquid states: Tomonaga-Luttinger liquid and spiral-. The two Kitaev points
and are singular. The
-dependent phase diagram is similar to that for the 2D honeycomb-lattice
KH model. Remarkably, all the ordered states of the honeycomb-lattice KH model
can be interpreted in terms of the coupled KH chains. We also discuss the
magnetic structure of the K-intercalated RuCl, a potential Kitaev material,
in the framework of the 1D KH model. Furthermore, we demonstrate that the
low-lying excitations of the 1D KH Hamiltonian can be explained within the
combination of the known six-vertex model and spin-wave theory
Quantum phase transitions in exactly solvable one-dimensional compass models
We present an exact solution for a class of one-dimensional compass models
which stand for interacting orbital degrees of freedom in a Mott insulator. By
employing the Jordan-Wigner transformation we map these models on
noninteracting fermions and discuss how spin correlations, high degeneracy of
the ground state, and symmetry in the quantum compass model are visible
in the fermionic language. Considering a zigzag chain of ions with singly
occupied orbitals ( orbital model) we demonstrate that the orbital
excitations change qualitatively with increasing transverse field, and that the
excitation gap closes at the quantum phase transition to a polarized state.
This phase transition disappears in the quantum compass model with maximally
frustrated orbital interactions which resembles the Kitaev model. Here we find
that finite transverse field destabilizes the orbital-liquid ground state with
macroscopic degeneracy, and leads to peculiar behavior of the specific heat and
orbital susceptibility at finite temperature. We show that the entropy and the
cooling rate at finite temperature exhibit quite different behavior near the
critical point for these two models.Comment: 15 pages, 14 figure
Quantum Phase Transition in the One-Dimensional Extended Quantum Compass Model in a Transverse Field
Quantum phase transitions in the one-dimensional extended quantum compass
model in transverse field are studied by using the Jordan-Wigner
transformation. This model is always gapful except at the critical surfaces
where the energy gap disappears. We obtain the analytic expressions of all
critical fields which drive quantum phase transitions. This model shows a rich
phase diagram which includes spin-flop, strip antiferromagnetic and saturate
ferromagnetic phases in addition to the phase with anti parallel ordering of
spin component on odd bonds. However we study the universality and scaling
properties of the transverse susceptibility and nearest-neighbor correlation
functions derivatives in different regions to confirm the results obtained
using the energy gap analysis.Comment: 8 Page, 15 Figure
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