818,871 research outputs found
Dimensionality, nematicity and Superconductivity in Fe-based systems
Study of Fe based compounds have drawn much attention due to the discovery of
superconductivity as well as many other exotic electronic properties. Here, we
review some of our works in these materials carried out employing density
functional theory and angle resolved photoemission spectroscopy. The results
presented here indicate that the dimensionality of the underlying electronic
structure plays important role in deriving their interesting electronic
properties. The nematicity found in most of these materials appears to be
related to the magnetic long range order. We argue that the exoticity in the
electronic properties are related to the subtlety in competing structural and
magnetic instabilities present in these materials.Comment: 7 figure
Electronic Correlation and Transport Properties of Nuclear Fuel Materials
Actinide elements, such as uranium and plutonium, and their compounds are
best known as nuclear materials. When engineering optimal fuel materials for
nuclear power, important thermophysical properties to be considered are melting
point and thermal conductivity. Understanding the physics underlying transport
phenomena due to electrons and lattice vibrations in actinide systems is a
crucial step toward the design of better fuels. Using first principle LDA+DMFT
method, we conduct a systematic study on the correlated electronic structures
and transport properties of select actinide carbides, nitrides, and oxides,
many of which are nuclear fuel materials. We find that different mechanisms,
electrons--electron and electron--phonon interactions, are responsible for the
transport in the uranium nitride and carbide, the best two fuel materials due
to their excellent thermophysical properties. Our findings allow us to make
predictions on how to improve their thermal conductivities.Comment: Main article: 5 pages, 3 figures. Supplementary info: 2 pages, 1
figur
Electron-phonon interaction and transport properties of metallic bulk and monolayer transition metal dichalcogenide TaS
Transition metal dichalcogenides have recently emerged as promising
two-dimensional materials with intriguing electronic properties. Existing
calculations of intrinsic phonon-limited electronic transport so far have
concentrated on the semicondcucting members of this family. In this paper we
extend these studies by investigating the influence of electron-phonon coupling
on the electronic transport properties and band renormalization of prototype
inherent metallic bulk and monolayer TaS. Based on density functional
perturbation theory and semi-classical Boltzmann transport calculations,
promising room temperature mobilities and sheet conductances are found, which
can compete with other established 2D materials, leaving TaS as promising
material candidate for transparent conductors or as atomically thin
interconnects. Throughout the paper, the electronic and transport properties of
TaS are compared to those of its isoelectronic counterpart TaSe and
additional informations to the latter are given. We furthermore comment on the
conventional su- perconductivity in TaS, where no phonon-mediated
enhancement of TC in the monolayer compared to the bulk state was found.Comment: accepted in IOPscience 2D Materials, supplemental material is
available on the publishers pag
Tailoring electronic properties of multilayer phosphorene by siliconization
Controlling a thickness dependence of electronic properties for
two-dimensional (2d) materials is among primary goals for their large-scale
applications. Herein, employing a first-principles computational approach, we
predict that Si interaction with multilayer phosphorene (2d-P) can result in
the formation of highly stable 2d-SiP and 2d-SiP compounds with a weak
interlayer interaction. Our analysis demonstrates that these systems are
semiconductors with band gap energies that can be governed by varying the
thickness and stacking order. Specifically, siliconization of phosphorene
allows to design 2d-SiP materials with significantly weaker thickness
dependence of electronic properties than that in 2d-P and to develop ways for
their tailoring. We also reveal the spatial dependence of electronic properties
for 2d-SiP highlighting difference in effective band gaps for different
layers. Particularly, our results show that central layers in the multilayer 2d
systems determine overall electronic properties, while the role of the
outermost layers is noticeably smaller
Novel approaches to spectral properties of correlated electron materials: From generalized Kohn-Sham theory to screened exchange dynamical mean field theory
The most intriguing properties of emergent materials are typically
consequences of highly correlated quantum states of their electronic degrees of
freedom. Describing those materials from first principles remains a challenge
for modern condensed matter theory. Here, we review, apply and discuss novel
approaches to spectral properties of correlated electron materials, assessing
current day predictive capabilities of electronic structure calculations. In
particular, we focus on the recent Screened Exchange Dynamical Mean-Field
Theory scheme and its relation to generalized Kohn-Sham theory. These concepts
are illustrated on the transition metal pnictide BaCoAs and elemental
zinc and cadmium.Comment: Accepted for publication in the Journal of the Physical Society of
Japa
Tuning the Dirac Cone of Bilayer and Bulk Structure Graphene by Intercalating First Row Transition Metals using First Principles Calculations
Modern nanoscience has focused on two-dimensional (2D) layer structure
materials which have garnered tremendous attention due to their unique
physical, chemical and electronic properties since the discovery of graphene in
2004. Recent advancement in graphene nanotechnology opens a new avenue of
creating 2D bilayer graphene (BLG) intercalates. Using first-principles DFT
techniques, we have designed 20 new materials \textit{in-silico} by
intercalating first row transition metals (TMs) with BLG, i.e. 10 layered
structure and 10 bulk crystal structures of TM intercalated in BLG. We
investigated the equilibrium structure and electronic properties of layered and
bulk structure BLG intercalated with first row TMs (Sc-Zn). The present DFT
calculations show that the 2 sub-shells of C atoms in graphene and the
3 sub-shells of the TM atoms provide the electron density near the
Fermi level controlling the material properties of the BLG-intercalated
materials. This article highlights how the Dirac point moves in both the BLG
and bulk-BLG given a different TM intercalated materials. The implications of
controllable electronic structure and properties of intercalated BLG-TM for
future device applications are discussed. This work opens up new avenues for
the efficient production of two-dimensional and three-dimensional carbon-based
intercalated materials with promising future applications in nanomaterial
science.Comment: 60 pages, 9 figures. arXiv admin note: text overlap with
arXiv:1701.03936 by other author
- …