141 research outputs found
Floating Zone Growth of Sr Substituted Han Purple: BaSrCuSiO
We present a route to grow single crystals of
BaSrCuSiO suitable for inelastic neutron studies
via the floating zone technique. Neutron single crystal diffraction was
utilized to check their bulk quality and orientation. Finally, the high quality
of the grown crystals was proven by X-ray diffraction and magnetic
susceptibility
Structural and magnetic properties of -LiIrO after grazing-angle focused ion beam thinning
Manipulating the size and orientation of quantum materials is often used to
tune emergent phenomena, but precise control of these parameters is also
necessary from an experimental point of view. Various synthesis techniques
already exist, such as epitaxial thin film growth and chemical etching, that
are capable of producing specific sample dimensions with high precision.
However, certain materials exist as single crystals that are often difficult to
manipulate, thereby limiting their studies to a certain subset of experimental
techniques. One particular class of these materials are the lithium and sodium
iridates that are promising candidates for hosting a Kitaev quantum spin liquid
state. Here we present a controlled method of using a focused ion beam at
grazing incidence to reduce the size of a -LiIrO single crystal
to a thickness of 1 . Subsequent x-ray diffraction measurements show the
lattice remains intact, albeit with a larger mosaic spread. The integrity of
the magnetic order is also preserved as the temperature dependent magnetic
diffraction peak follows the same trend as its bulk counterpart with a
transition temperature at TN = 37.5 K. Our study demonstrates a technique that
opens up the possibility of nonequilibrium experiments where submicron thin
samples are often essential
Crystal-electric-field excitations in a quantum-spin-liquid candidate NaErS
The delafossite family of compounds with a triangular lattice of rare earth
ions has been recently proposed as a candidate host for quantum spin liquid
(QSL) states. To realize QSLs, the crystal-electric-field (CEF) ground state of
the rare earth ions should be composed of a doublet that allows sizable quantum
tunneling, but till now the knowledge on CEF states in the delafossite
compounds is still limited. Here we employ inelastic neutron scattering (INS)
to study the CEF transitions in a powder sample of the delafossite NaErS,
where the large total angular momentum of the Er ions and
the resulting plethora of CEF transitions enable an accurate fit of the CEF
parameters. Our study reveals nearly isotropic spins with large
components for the Er CEF ground states, which might facilitate the
development of a QSL state. The scaling of the obtained CEF Hamiltonian to
different rare earth ions suggests that sizable components are
generally present in the CEF ground states, supporting the ternary sulfide
delafossites as potential QSL hosts.Comment: 7 pages, 5 figures, with updated XRD refinement and CEF analysi
Nonlinear quantum magnetophononics in SrCu(BO)
Harnessing the most advanced capabilities of quantum technologies will
require the ability to control macroscopic quantum states of matter. Quantum
magnetic materials provide a valuable platform for realizing highly entangled
many-body quantum systems, and have been used to investigate phenomena ranging
from quantum phase transitions (QPTs) to fractionalization, topological order
and the entanglement structure of the quantum wavefunction. Although multiple
studies have controlled their properties by static applied pressures or
magnetic fields, dynamical control at the fundamental timescales of their
magnetic interactions remains completely unexplored. However, major progress in
the technology of ultrafast laser pulses has enabled the dynamical modification
of electronic properties, and now we demonstrate the ultrafast control of
quantum magnetism. This we achieve by a magnetophononic mechanism, the driving
of coherent lattice displacements to produce a resonant excitation of the
quantum spin dynamics. Specifically, we apply intense terahertz laser pulses to
excite a collective spin state of the quantum antiferromagnet
SrCu(BO) by resonance with the nonlinear mixing frequency of the
driven phonons that modulate the magnetic interactions. Our observations
indicate a universal mechanism for controlling nonequilibrium quantum many-body
physics on timescales many orders of magnitude faster than those achieved to
date.Comment: 24 pages, 9 figure
Statics and dynamics of weakly coupled antiferromagnetic spin-1/2 ladders in a magnetic field
We investigate weakly coupled spin-1/2 ladders in a magnetic field. The work
is motivated by recent experiments on the compound (C5H12N)2CuBr4 (BPCB). We
use a combination of numerical and analytical methods, in particular the
density matrix renormalization group (DMRG) technique, to explore the phase
diagram and the excitation spectra of such a system. We give detailed results
on the temperature dependence of the magnetization and the specific heat, and
the magnetic field dependence of the nuclear magnetic resonance (NMR)
relaxation rate of single ladders. For coupled ladders, treating the weak
interladder coupling within a mean-field or quantum Monte Carlo approach, we
compute the transition temperature of triplet condensation and its
corresponding antiferromagnetic order parameter. Existing experimental
measurements are discussed and compared to our theoretical results. Furthermore
we compute, using time dependent DMRG, the dynamical correlations of a single
spin ladder. Our results allow to directly describe the inelastic neutron
scattering cross section up to high energies. We focus on the evolution of the
spectra with the magnetic field and compare their behavior for different
couplings. The characteristic features of the spectra are interpreted using
different analytical approaches such as the mapping onto a spin chain, a
Luttinger liquid (LL) or onto a t-J model. For values of parameters for which
such measurements exist, we compare our results to inelastic neutron scattering
experiments on the compound BPCB and find excellent agreement. We make
additional predictions for the high energy part of the spectrum that are
potentially testable in future experiments.Comment: 35 pages, 26 figure
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