156 research outputs found
Turning a Band Insulator Into an Exotic Superconductor
Understanding exotic, non s--wave--like states of Cooper pairs is important
and may lead to new superconductors with higher critical temperatures and novel
properties. Their existence is known to be possible but has always been thought
to be associated with non--traditional mechanisms of superconductivity where
electronic correlations play an important role. Here we use a first principles
linear response calculation to show that in doped BiSe an
unconventional p--wave--like state can be favored via a conventional
phonon--mediated mechanism, as driven by an unusual, almost singular behavior
of the electron--phonon interaction at long wavelengths. This may provide a new
platform for our understanding superconductivity phenomena in doped band
insulators.Comment: Published versio
Computational Design of Axion Insulators Based on 5d Spinels Compounds
Based on density functional calculation with LDA+U method, we propose that
hypothetical Osmium compounds such as CaOs2O4 and SrOs2O4 can be stabilized in
the geometrically frustrated spinel crystal structure. They also show some
exotic electronic and magnetic properties in a reasonable range of on-site
Coulomb correlation U such as ferromagnetism and orbital magnetoelectric effect
characteristic to Axion electrodynamics. Other electronic phases including 3D
Dirac metal and Mott insulator exist and would make perspective 5d spinels
ideal for applications.Comment: 5 pages, 3 figure
Electronic Structure and Linear Optical Properties of SrCuOCl Studied from the First Principles Calculation
First-principles calculations with the full-potential linearized augmented
plane-wave (FP-LAPW) method have been performed to investigate detailed
electronic and linear optical properties of SrCuOCl, which is
a classical low-dimensional antiferromagnet (AFM) charge transfer ({\it CT})
insulator. Within the local-spin-density approximation (LSDA) plus the on-site
Coulomb interaction (LADA+) added on Cu 3d orbitals, our calculated band
gap and spin moments are well consistent with the experimental and other
theoretical values. The energy dispersion relation agrees well with the angle
resolved photoemission measurements. Its linear optical properties are
calculated within the electric-dipole approximation. The absorption spectrum is
found to agree well with the experimental result.Comment: 5 pages, 5 figure
Efficient Topological Materials Discovery Using Symmetry Indicators
Although the richness of spatial symmetries has led to a rapidly expanding
inventory of possible topological crystalline (TC) phases of electrons,
physical realizations have been slow to materialize due to the practical
difficulty to ascertaining band topology in realistic calculations. Here, we
integrate the recently established theory of symmetry indicators of band
topology into first-principle band-structure calculations, and test it on a
databases of previously synthesized crystals. The combined algorithm is found
to efficiently unearth topological materials and predict topological properties
like protected surface states. On applying our algorithm to just 8 out of the
230 space groups, we already discover numerous materials candidates displaying
a diversity of topological phenomena, which are simultaneously captured in a
single sweep. The list includes recently proposed classes of TC insulators that
had no previous materials realization as well as other topological phases,
including: (i) a screw-protected 3D TC insulator, \b{eta}-MoTe2, with gapped
surfaces except for 1D helical "hinge" states; (ii) a rotation-protected TC
insulator BiBr with coexisting surface Dirac cones and hinge states; (iii)
non-centrosymmetric Z2 topological insulators undetectable using the
well-established parity criterion, AgXO (X=Na,K,Rb); (iv) a Dirac semimetal
MgBi2O6; (v) a Dirac nodal-line semimetal AgF2; and (vi) a metal with
three-fold degenerate band crossing near the Fermi energy, AuLiMgSn. Our work
showcases how the recent theoretical insights on the fundamentals of band
structures can aid in the practical goal of discovering new topological
materials
Robust Half-Metallic Character and Large Oxygen Magnetism in a Perovskite Cuprate
The new perovskite cuprate material SrCaReCuO, which
behaves ferrimagnetically and shows an unusually high Curie temperature ( 440 K), is found from density-functional theory calculation to display
several surprising properties after hole doping or chemical substitution: (1)
Half metal (HM) is realized by replacing Re with W or Mo while remains
high; (2) hole-doped SrCaReCuO is also HM with high
. Moreover, we find that the O atoms will carry a large magnetic moment
after hole doping, which is in sharp contrast with the generally accepted
concept that magnetism in solid requires partially filled shells of or
electrons in cations. The material SrCaReCuO is therefore
expected to provide a very useful platform for material design and development.Comment: 5 pages and 4 figure
- …