289 research outputs found
Growth, Characterization, Vortex Pinning and Vortex Flow Properties of Single Crystals of Iron Chalcogenide Superconductor FeCrSe
We report the growth and characterization of single crystals of iron
chalcogenide superconductor FeCrSe. There is an enhancement of the
superconducting transition temperature (T) as compared to the T of the single crystals of the parent compound FeSe by about 25%.
The superconducting parameters such as the critical fields, coherence length,
penetration depth and the Ginzburg-Landau parameter have been estimated for
these single crystals. Analysis of the critical current data suggests a
fluctuation in electronic mean free path induced () pinning mechanism
in this material. Thermally activated transport across the superconducting
transition in the presence of external magnetic fields suggests a crossover
from a single vortex pinning regime at low fields to a collective flux creep
regime at higher magnetic fields. The nature of charge carriers in the normal
state estimated from the Hall effect and thermal transport measurements could
provide crucial information on the mechanism of superconductivity in Fe-based
materials.Comment: 2 additional figures, additional discussion on nature of charge
carrier
Tunnelling Characteristics of Stone-Wales Defects in Monolayers of Sn and Group-V Elements
Topological defects in ultrathin layers are often formed during synthesis and
processing, thereby, strongly influencing their electronic properties . In this
paper, we investigate the role of Stone-Wales (SW) defects in modifying the
electronic properties of the monolayers of Sn and group-V elements. The
calculated results find the electronic properties of stanene (monolayer of Sn
atoms) to be strongly dependent on the concentration of SW-defects e.g.,
defective stanene has nearly zero band gap (~ 0.03 eV) for the defect
concentration of 2.2 x 10^13 cm^-2 which opens up to 0.2 eV for the defect
concentration of 3.7 x 10^13 cm^-2. In contrast, SW-defects appear to induce
conduction states in the semiconducting monolayers of group-V elements. These
conduction states act as channels for electron tunnelling, and the calculated
tunnelling characteristics show the highest differential conductance for the
negative bias with the asymmetric current-voltage characteristics. On the other
hand, the highest differential conductance was found for the positive bias in
stanene. Simulated STM topographical images of stanene and group-V monolayers
show distinctly different features in terms of their cross-sectional views and
distance-height profiles which can serve as fingerprints to identify the
topological defects in the monolayers of group-IV and group-V elements in
experiments.Comment: 18 pages, 5 figures, 1 tabl
Two Dimensional Allotropes of Arsenene with Wide Range of High and Anisotropic Carrier Mobility
Considering the rapid development of experimental techniques for fabricating
2D materials in recent years, various monolayers are expected to be
experimentally realized in the near future. Motivated by the recent research
activities focused on the honeycomb arsenene monolayers, stability and carrier
mobility of non-honeycomb and porous allotropic arsenene are determined using
first principles calculations. In addition to five honeycomb structures of
arsenene, a total of eight other structures are considered in this study. An
extensive analysis comprising energetics, phonon spectra and mechanical
properties confirms that these structures are energetically and dynamically
stable. All these structures are semiconductors with a broad range of band gap
varying from ~1 eV to ~2.5 eV. Significantly, these monolayer allotropes
possess anisotropic carrier mobilities as high as several hundred
cm^{2}V^{-1}s^{-1} which is comparable with the well-known 2D materials such as
black phosphorene and monolayer MoS_{2}. Combining such broad band gaps and
superior carrier mobilities, these monolayer allotropes can be promising
candidates for the superior performance of the next generation nanoscale
devices. We further explore these monolayer allotropes for photocatalytic water
splitting and find that arsenene monolayers have potential for usage as visible
light driven photocatalytic water splitting.Comment: 31 pages, 8 figures, 3 table
In-silico designing of an inhibitor against mTOR FRB domain: Therapeutic implications against breast cancer
Worldwide breast cancer causes significant fatalities in women. The effective therapeutic solution for treating the disease is using new and probable antagonistic biologically available ligands as anticancer drugs. To identify a successful therapeutic approach, the scientific community is now interested in creating novel ligands that in the future may be used as anticancer drugs. The mechanistic target of rapamycin (mTOR) is a protein kinase connected to several processes governing immunity, metabolism, cell development, and survival. The proliferation and metastasis of tumors have both been linked to the activation of the mTOR pathway. Female breast cancer represents about 15.3% of all new cancer cases in the U.S. alone and is frequently diagnosed among women aged 55 to 69 years. Given that the P13K/AKT/mTOR pathway is one of the most often activated in cancer, much attention has been paid to its resistance as a novel oncological treatment approach. mTOR/FRB Domain’s recruitment cleft as, well as substrate recruitment mechanism, was targeted using a structural-based approach. A series of selective inhibitory small molecules have been designed and screened for the best inhibiting target binding triad of the FRB Domain with better ADME and no detectable toxic effects
Macroscopic chirality of twist-bend nematic phase in bent dimers confirmed by circular dichroism
Many achiral bent molecules and some polymers with such repeat units exhibit a liquid crystal phase transition between a conventional nematic (N), and a second nematic (Nx) with periodically modulated orientation. Theory predicts several possible structures for the Nx phase, some of which are chiral (helical), and others achiral (e.g. zigzag). Experimentally distinguishing which modulation type is present is non-trivial and the structure is often assumed to be helical despite the other possibilities. Here we use circular dichroism (CD) spectroscopy to directly and unambiguously identify chirality in the Nx phase of two different dimer series, “DTC5Cn” and “CBCnCB”, which vary in (CH2)n spacer length (n=5, 7, 9). In doing so we have determined that the modulation type is helical in all samples. The temperature dependence of the CD signal was also investigated, suggesting that the helical structure progressively unwinds on approach to the high temperature N phas
Low-frequency dielectric processes in deformed helix ferroelectric liquid crystals
A low-frequency dielectric relaxation mode in deformed helix ferroelectric liquid crystal (DHFLC) has been observed at the interface of strongly rubbed substrates and DHFLC material which may find applications in low power consumption FLC devices. The surface-induced dielectric relaxation process at the interface of DHFLC and substrate is called the partially unwound helical mode (p-UHM) due to the unwinding of the helical structure at this interface. After investigation of the material under various parameters such as temperature, variation of the amplitude of probing ac voltage and dc bias voltage, the relaxation frequency of p-UHM is found to be shifted towards Goldstone mode and merged with it. The relaxation frequency of Goldstone mode is found to decrease, whereas the relaxation frequency of p-UHM process increases with the increase in temperature of DHFLC. Finally, both the modes merge and the resultant relaxation frequency is found to be lower than Goldstone mode in SmC* phase. It seems that phason mode and partial helical unwinding mode are coupled together due to dipole moment that is resulting in a new relaxation frequency. p-UHM process is significant for low-power displays and non-displays applications like a part of sensor where weak electric signal is required to be realized without pre-amplification
Magnetization hysteresis and time decay measurements in FeSeTe : Evidence for fluctuation in mean free path induced pinning
We present results of magnetic measurements relating to vortex phase diagram
in a single crystal of FeSeTe which displays second
magnetization peak anomaly for . The possible role of the
crystalline anisotropy on vortex pinning is explored via magnetic torque
magnetometry. We present evidence in favor of pinning related to spatial
variations of the charge carrier mean free path leading to small bundle vortex
pinning by randomly distributed (weak) pinning centers for both
and . This is further corroborated using magnetization data for in a single crystal of FeSeTe. Dynamical
response across second magnetization peak (SMP) anomaly in
FeSeTe has been compared with that across the well researched
phenomenon of peak effect (PE) in a single crystal of CeRu.Comment: 11 figures, provided additional data in another sample, added Fig.
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