463 research outputs found
Berry phase induced dimerization in one-dimensional quadrupolar systems
We investigate the effect of the Berry phase on quadrupoles that occur for
example in the low-energy description of spin models. Specifically we study
here the one-dimensional bilinear-biquadratic spin-one model. An open question
for many years about this model is whether it has a non-dimerized fluctuating
nematic phase. The dimerization has recently been proposed to be related to
Berry phases of the quantum fluctuations. We use an effective low-energy
description to calculate the scaling of the dimerization according to this
theory, and then verify the predictions using large scale density-matrix
renormalization group (DMRG) simulations, giving good evidence that the state
is dimerized all the way up to its transition into the ferromagnetic phase. We
furthermore discuss the multiplet structure found in the entanglement spectrum
of the ground state wave functions.Comment: 4.5 pages + 4 pages supplementary material, 4 figure
Ground-state phase diagram of an anisotropic spin- model on the triangular lattice
Motivated by the recent experiment on a rare-earth material YbMgGaO [Y.
Li \textit{et al.}, Phys. Rev. Lett. \textbf{115}, 167203 (2015)], which found
that the ground state of YbMgGaO is a quantum spin liquid, we study the
ground-state phase diagram of an anisotropic spin- model that was proposed
to describe YbMgGaO. Using the density-matrix renormalization group method
in combination with the exact diagonalization, we calculate a variety of
physical quantities, including the ground-state energy, the fidelity, the
entanglement entropy and spin-spin correlation functions. Our studies show that
in the quantum phase diagram there is a phase and two distinct
stripe phases. The transitions from the two stripe phases to the
phase are of the first order. However, the transition between the two stripe
phases is not the first order, which is different from its classical
counterpart. Additionally, we find no evidence for a quantum spin liquid in
this model. Our results suggest that additional terms may be also important to
model the material YbMgGaO. These findings will stimulate further
experimental and theoretical works in understanding the quantum spin liquid
ground state in YbMgGaO.Comment: minor change
Ground-state phase diagram of the frustrated spin-1/2 two-leg honeycomb ladder
We investigate a spin- two-leg honeycomb ladder with frustrating
next-nearest-neighbor (NNN) coupling along the legs, which is equivalent to two
- spin chains coupled with at odd rungs. The full parameter
region of the model is systematically studied using conventional and infinite
density-matrix renormalization group as well as bosonization. The rich phase
diagram consists of five distinct phases: A Haldane phase, a NNN-Haldane phase
and a staggered dimer phase when ; a rung singlet phase and a
columnar dimer phase when . An interesting reentrant behavior
from the dimerized phase into the Haldane phase is found as the frustration
increases. The universalities of the critical phase transitions are fully
analyzed. Phase transitions between dimerized and disordered phases belong to
the two-dimensional Ising class with central charge . The transition
from the Haldane phase to NNN-Haldane phase is of a weak topological first
order, while the continuous transition between the Haldane phase and rung
singlet phase has central charge .Comment: 14 pages, 17 figures, for latest version and additional information
see https://www.physik.uni-kl.de/eggert/papers/index.htm
Accurate determination of the Gaussian transition in spin-1 chains with single-ion anisotropy
The Gaussian transition in the spin-one Heisenberg chain with single-ion
anisotropy is extremely difficult to treat, both analytically and numerically.
We introduce an improved DMRG procedure with strict error control, which we use
to access very large systems. By considering the bulk entropy, we determine the
Gaussian transition point to 4-digit accuracy, , resolving a long-standing debate in quantum magnetism. With
this value, we obtain high-precision data for the critical behavior of
quantities including the ground-state energy, gap, and transverse string-order
parameter, and for the critical exponent, . Applying our
improved technique at highlights essential differences in
critical behavior along the Gaussian transition line.Comment: 4 pages and 4 figure
The evolution of magnetic structure driven by a synthetic spin-orbit coupling in two-component Bose-Hubbard model
We study the evolution of magnetic structure driven by a synthetic spin-orbit
coupling in a one-dimensional two-component Bose-Hubbard model. In addition to
the Mott insulator-superfluid transition, we found in Mott insulator phases a
transition from a gapped ferromagnetic phase to a gapless chiral phase by
increasing the strength of spin-orbit coupling. Further increasing the
spin-orbit coupling drives a transition from the gapless chiral phase to a
gapped antiferromagnetic phase. These magnetic structures persist in superfluid
phases. In particular, in the chiral Mott insulator and chiral superfluid
phases, incommensurability is observed in characteristic correlation functions.
These unconventional Mott insulator phase and superfluid phase demonstrate the
novel effects arising from the competition between the kinetic energy and the
spin-orbit coupling.Comment: 9 fig; English polished, note adde
(R)-(−)-N-Isovalerylcamphorsultam
The title compound, C15H25NO3S, was prepared from (R)-(−)camphorsultam and isovaleryl chloride. The asymetric unit contains two independent molecules with slightly different conformations. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link molecules into two independent hydrogen-bonded chains propagating along the a and b axes
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