27 research outputs found
Enhanced superconductivity in SnSb under pressure: A first principles study
First principles electronic structure calculations reveal both SnP and SnSb to be stable in the NaCl structure. In SnSb, a first order phase transition from NaCl to CsCl type structure is observed at around 13\,, which is also confirmed from enthalpy calculations and agrees well with experimental and other theoretical reports. Calculations of the phonon spectra and hence the electron-phonon coupling, , and superconducting transition temperature, , at zero pressure for both the compounds and at high pressure for SnSb were performed. These calculations report of 0.614 and 3.083 for SnP and SnSb respectively, in the NaCl structure, in good agreement with experiment whilst at the transition pressure, in the CsCl structure, a drastically increased value of around 9.18 (9.74 at 20 ) is found for SnSb together with a dramatic increase in the electronic density of states at this pressure. The lowest energy acoustic phonon branch in each structure also demonstrate some softening effects, which are well addressed in this work.
Electronic topological transitions in Nb3X (X = Al, Ga, In, Ge, and Sn) under compression investigated by first principles calculations
First principles electronic structure calculations of A-15 type Nb3X (X = Al, Ga, In, Ge, and Sn) compounds are performed at ambient and high pressures. Mechanical stability is confirmed in all the compounds both at ambient as well as under compression from the calculated elastic constants. We have observed four holes and two electron Fermi surfaces (FS) for all the compounds studied and FS nesting feature is observed at M and along X-Γ in all the compounds. A continuous change in the FS topology is observed under pressure in all the compounds which is also reflected in the calculated elastic constants and density of states under pressure indicating the Electronic topological transitions (ETT). The ETT observed at around 21.5 GPa, 17.5 GPa in Nb3Al and Nb3Ga are in good agreement with the anomalies observed by the experiments
Observation of Symmetry-Protected Dirac States in Nonsymmorphic -Antimonene
Two-dimensional (2D) Dirac states with linear band dispersion have attracted
enormous interest since the discovery of graphene. However, to date, 2D Dirac
semimetals are still very rare due to the fact that 2D Dirac states are
generally fragile against perturbations such as spin-orbit couplings.
Nonsymmorphic crystal symmetries can enforce the formation of Dirac nodes,
providing a new route to establishing symmetry-protected Dirac states in 2D
materials. Here we report the symmetry-protected Dirac states in nonsymmorphic
alpha-antimonene. The antimonene was synthesized by the method of molecular
beam epitaxy. Two Dirac cones with large anisotropy were observed by
angle-resolved photoemission spectroscopy. The Dirac state in alpha-antimonene
is of spin-orbit type in contrast to the spinless Dirac states in graphene. The
result extends the 'graphene' physics into a new family of 2D materials where
spin-orbit coupling is present.Comment: 4 figure
Nonlinear and nonreciprocal transport effects in untwinned thin films of ferromagnetic Weyl metal SrRuO
The identification of distinct charge transport features, deriving from
nontrivial bulk band and surface states, has been a challenging subject in the
field of topological systems. In topological Dirac and Weyl semimetals,
nontrivial conical bands with Fermi-arc surfaces states give rise to negative
longitudinal magnetoresistance due to chiral anomaly effect and unusual
thickness dependent quantum oscillation from Weyl-orbit effect, which were
demonstrated recently in experiments. In this work, we report the experimental
observations of large nonlinear and nonreciprocal transport effects for both
longitudinal and transverse channels in an untwinned Weyl metal of SrRuO
thin film grown on a SrTiO substrate. From rigorous measurements with
bias current applied along various directions with respect to the crystalline
principal axes, the magnitude of nonlinear Hall signals from the transverse
channel exhibits a simple sin dependent at low temperatures, where
is the angle between bias current direction and orthorhombic
[001], reaching a maximum when current is along orthorhombic
[1-10]. On the contrary, the magnitude of nonlinear and nonreciprocal
signals in the longitudinal channel attains a maximum for bias current along
[001], and it vanishes for bias current along [1-10]. The
observed -dependent nonlinear and nonreciprocal signals in longitudinal
and transverse channels reveal a magnetic Weyl phase with an effective Berry
curvature dipole along [1-10] from surface states, accompanied by 1D
chiral edge modes along [001].Comment: 24 pages, 6 figure
Tuberculosis chemotherapy: current drug delivery approaches
Tuberculosis is a leading killer of young adults worldwide and the global scourge of multi-drug resistant tuberculosis is reaching epidemic proportions. It is endemic in most developing countries and resurgent in developed and developing countries with high rates of human immunodeficiency virus infection. This article reviews the current situation in terms of drug delivery approaches for tuberculosis chemotherapy. A number of novel implant-, microparticulate-, and various other carrier-based drug delivery systems incorporating the principal anti-tuberculosis agents have been fabricated that either target the site of tuberculosis infection or reduce the dosing frequency with the aim of improving patient outcomes. These developments in drug delivery represent attractive options with significant merit, however, there is a requisite to manufacture an oral system, which directly addresses issues of unacceptable rifampicin bioavailability in fixed-dose combinations. This is fostered by the need to deliver medications to patients more efficiently and with fewer side effects, especially in developing countries. The fabrication of a polymeric once-daily oral multiparticulate fixed-dose combination of the principal anti-tuberculosis drugs, which attains segregated delivery of rifampicin and isoniazid for improved rifampicin bioavailability, could be a step in the right direction in addressing issues of treatment failure due to patient non-compliance