123 research outputs found
Effect of magnetic field on the spin resonance in FeTe(0.5)Se(0.5) as seen via inelastic neutron scattering
Inelastic neutron scattering and susceptibility measurements have been
performed on the optimally-doped Fe-based superconductor FeTe(0.5)Se(0.5),
which has a critical temperature, Tc of 14 K. The magnetic scattering at the
stripe antiferromagnetic wave-vector Q = (0.5,0.5) exhibits a "resonance" at ~
6 meV, where the scattering intensity increases abruptly when cooled below Tc.
In a 7-T magnetic field parallel to the a-b plane, Tc is slightly reduced to ~
12 K, based on susceptibility measurements. The resonance in the neutron
scattering measurements is also affected by the field. The resonance intensity
under field cooling starts to rise at a lower temperature ~ 12 K, and the low
temperature intensity is also reduced from the zero-field value. Our results
provide clear evidence for the intimate relationship between superconductivity
and the resonance measured in magnetic excitations of Fe-based superconductors.Comment: 4 pages, 3 figure
Short-range incommensurate magnetic order near the superconducting phase boundary in Fe(1+d)Te(1-x)Se(x)
We performed elastic neutron scattering and magnetization measurements on
Fe(1.07)Te(0.75)Se(0.25) and FeTe(0.7)Se(0.3). Short-range incommensurate
magnetic order is observed in both samples. In the former sample with higher Fe
content, a broad magnetic peak appears around (0.46,0,0.5) at low temperature,
while in FeTe(0.7)Se(0.3) the broad magnetic peak is found to be closer to the
antiferromagnetic (AFM) wave-vector (0.5,0,0.5). The incommensurate peaks are
only observed on one side of the AFM wave-vector for both samples, which can be
modeled in terms of an imbalance of ferromagnetic/antiferromagnetic
correlations between nearest-neighbor spins. We also find that with higher Se
(and lower Fe) concentration, the magnetic order becomes weaker while the
superconducting temperature and volume increase.Comment: Version as appeared in PR
TPH-2 polymorphisms interact with early life stress to influence response to treatment with antidepressant drugs
Background: Variation in genes implicated in monoamine neurotransmission may interact with environmental factors to influence antidepressant response. We aimed to determine how a range of single nucleotide polymorphisms in monoaminergic genes influence this response to treatment and how they interact with childhood trauma and recent life stress in a Chinese sample. An initial study of monoaminergic coding region single nucleotide polymorphisms identified significant associations of TPH2 and HTR1B single nucleotide polymorphisms with treatment response that showed interactions with childhood and recent life stress, respectively (Xu et al., 2012).
Methods: A total of 47 further single nucleotide polymorphisms in 17 candidate monoaminergic genes were genotyped in 281 Chinese Han patients with major depressive disorder. Response to 6 weeks’ antidepressant treatment was determined by change in the 17-item Hamilton Depression Rating Scale score, and previous stressful events were evaluated by the Life Events Scale and Childhood Trauma Questionnaire-Short Form.
Results: Three TPH2 single nucleotide polymorphisms (rs11178998, rs7963717, and rs2171363) were significantly associated with antidepressant response in this Chinese sample, as was a haplotype in TPH2 (rs2171363 and rs1487278). One of these, rs2171363, showed a significant interaction with childhood adversity in its association with antidepressant response.
Conclusions: These findings provide further evidence that variation in TPH2 is associated with antidepressant response and may also interact with childhood trauma to influence outcome of antidepressant treatment
Optical and Electronic Properties of Femtosecond Laser-Induced Sulfur-Hyperdoped Silicon N+/P Photodiodes
Impurity-mediated near-infrared (NIR) photoresponse in silicon is of great interest for photovoltaics and photodetectors. In this paper, we have fabricated a series of n+/p photodetectors with hyperdoped silicon prepared by ion-implantation and femtosecond pulsed laser. These devices showed a remarkable enhancement on absorption and photoresponse at NIR wavelengths. The device fabricated with implantation dose of 1014 ions/cm2 has exhibited the best performance. The proposed method offers an approach to fabricate low-cost broadband silicon-based photodetectors
One-Step Clustering with Adaptively Local Kernels and a Neighborhood Kernel
Among the methods of multiple kernel clustering (MKC), some adopt a neighborhood kernel as the optimal kernel, and some use local base kernels to generate an optimal kernel. However, these two methods are not synthetically combined together to leverage their advantages, which affects the quality of the optimal kernel. Furthermore, most existing MKC methods require a two-step strategy to cluster, i.e., first learn an indicator matrix, then executive clustering. This does not guarantee the optimality of the final results. To overcome the above drawbacks, a one-step clustering with adaptively local kernels and a neighborhood kernel (OSC-ALK-ONK) is proposed in this paper, where the two methods are combined together to produce an optimal kernel. In particular, the neighborhood kernel improves the expression capability of the optimal kernel and enlarges its search range, and local base kernels avoid the redundancy of base kernels and promote their variety. Accordingly, the quality of the optimal kernel is enhanced. Further, a soft block diagonal (BD) regularizer is utilized to encourage the indicator matrix to be BD. It is helpful to obtain explicit clustering results directly and achieve one-step clustering, then overcome the disadvantage of the two-step strategy. In addition, extensive experiments on eight data sets and comparisons with six clustering methods show that OSC-ALK-ONK is effective
VASP2KP: kp models and Lande g-factors from ab initio calculations
The method is significant in condensed matter physics for the
compact and analytical Hamiltonian. In the presence of magnetic field, it is
described by the effective Zeeman's coupling Hamiltonian with Land\'e -factors. Here, we develop an open-source package VASP2KP (including two
parts: vasp2mat and mat2kp) to compute parameters and Land\'e
-factors directly from the wavefunctions provided by the density functional
theory (DFT) as implemented in Vienna ab initio Simulation Package (VASP).
First, we develop a VASP patch vasp2mat to compute matrix representations of
the generalized momentum operator , spin operator , time reversal
operator and crystalline symmetry operators on the DFT
wavefunctions. Second, we develop a python code mat2kp to obtain the unitary
transformation that rotates the degenerate DFT basis towards the standard
basis, and then automatically compute the parameters and
-factors. The theory and the methodology behind VASP2KP are described in
detail. The matrix elements of the operators are derived comprehensively and
computed correctly within the projector augmented wave method. We apply this
package to some materials, e.g., BiSe, NaBi, Te, InAs and 1H-TMD
monolayers. The obtained effective model's dispersions are in good agreement
with the DFT data around the specific wave vector, and the -factors are
consistent with experimental data. The VASP2KP package is available at
https://github.com/zjwang11/VASP2KP
All-fiber normal-dispersion single-polarization passively mode-locked laser based on a 45°-tilted fiber grating
An all-fiber normal-dispersion Yb-doped fiber laser with 45- tilted fiber grating (TFG) isto the best of our knowledgeexperimentally demonstrated for the first time. Stable linearly-chirped pulses with the duration of 4 ps and the bandwidth of 9 nm can be directly generated from the laser cavity. By employing the 45 TFG with the polarization-dependent loss of 33 dBoutput pulses with high polarization extinction ratio of 26 dB are implemented in the experiment. Our result shows that the 45 TFG can work effectively as a polarizerwhich could be exploited to singlepolarization all-fiber lasers
Landau level splitting in Cd3As2 under high magnetic fields
Three-dimensional topological Dirac semimetals (TDSs) are a new kind of Dirac
materials that exhibit linear energy dispersion in the bulk and can be viewed
as three-dimensional graphene. It has been proposed that TDSs can be driven to
other exotic phases like Weyl semimetals, topological insulators and
topological superconductors by breaking certain symmetries. Here we report the
first transport experiment on Landau level splitting in TDS Cd3As2 single
crystals under high magnetic fields, suggesting the removal of spin degeneracy
by breaking time reversal symmetry. The detected Berry phase develops an
evident angular dependence and possesses a crossover from nontrivial to trivial
state under high magnetic fields, a strong hint for a fierce competition
between the orbit-coupled field strength and the field-generated mass term. Our
results unveil the important role of symmetry breaking in TDSs and further
demonstrate a feasible path to generate a Weyl semimetal phase by breaking time
reversal symmetry.Comment: 31 page
- …