1,720,984 research outputs found
Bulk photovoltaic effect in ferroelectric and antiferroelectric phases of antimony sulphoiodide investigated by means of ab-initio simulations
No full textWe employ first-principles calculations to investigate the ferroelectric properties and the bulk photovoltaic effect (BPVE) of antimony sulfur iodide (SbSI). The BPVE enables direct sunlight-to-electricity conversion in homogeneous materials and, in ferroelectric compounds, can be tuned via an electric field controlling the polarization. However, most ferroelectrics are oxides with large band gaps exceeding the energy of visible light, thereby limiting their photovoltaic performance. SbSI, featuring a visible-range band gap, combines remarkable photovoltaic capabilities with a spin-textured band structure, coupling charge and spin degrees of freedom. Our calculations predict ferroelectric and antiferroelectric phases with comparable band gaps but distinct spin textures, relevant for spintronics applications. The BPVE is driven by the linear and circular photogalvanic effects, exhibiting high photoconductivities under visible light. Furthermore, it serves as a diagnostic tool to identify the material phase, with the circular photogalvanic effect reflecting spin texture changes. Thanks to its multifunctional properties, SbSI emerges as a promising candidate for solar energy conversion and advanced electronics, with potential applications extending to spintronics
Low energy bands and transport properties of chromium arsenide
No full textWe apply a method that combines the tight-binding approximation and the Lö wdin down-folding procedure to evaluate the electronic band structure of the newly discovered pressure-induced superconductor CrAs. By integrating out all low-lying arsenic degrees of freedom, we derive an effective Hamiltonian model describing the Cr d bands near the Fermi level. We calculate and make predictions for the energy spectra, the Fermi surface, the density of states and transport and magnetic properties of this compound. Our results are consistent with local-density approximation calculations and they also show good agreement with available experimental data for resistivity and the Cr magnetic moment
Tuning interchain ferromagnetic instability in A2Cr3As3 ternary arsenides by chemical pressure and uniaxial strain
No full textA minimal tight-binding model for the quasi-one-dimensional superconductor K2Cr3As3
Full text linkWe present a systematic derivation of a minimal five-band tight-binding model for the description of the electronic structure of the recently discovered quasi-one-dimensional superconductor K2Cr3As3. Taking as a reference the density-functional theory (DFT) calculation, we use the outcome of a Löwdin procedure to refine a Wannier projection and fully exploit the predominant weight at the Fermi level of the states having the same symmetry of the crystal structure. Such states are described in terms of five quasi-atomic d orbitals: four planar orbitals, two d xy and two , and a single out-of-plane one, . We show that this minimal model reproduces with great accuracy the DFT band structure in a broad energy window around the Fermi energy. Moreover, we derive an explicit simplified analytical expression of such model, which includes three nearest-neighbor (NN) hopping terms along the z direction and one NN term within the xy plane. This model captures very efficiently the energy spectrum of the system and, consequently, can be used to study transport properties, superconductivity and dynamical effects in this novel class of superconductors
Multiple band crossings and Fermi surface topology: Role of double nonsymmorphic symmetries in MnP-type crystal structures
Full text linkIntrachain collinear magnetism and interchain magnetic phases in Cr3As3−K-based materials
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Magnetic instabilities in quasi-one-dimensional Cr-based material
Full text linkThe magnetic response of a K2Cr3As3 sample has been studied by means of dc
magnetization measurements as a function of magnetic field (H) at different
temperatures ranging from 5 K up to 300 K. Looking at the magnetic hysteresis
loops m(H), a diamagnetic behavior of the sample has been inferred at
temperatures higher than 60 K, whereas at lower temperatures the sample shows a
hysteresis loop compatible with the presence of ferrimagnetism. Moreover,
several spike-like magnetization jumps, both positive and negative, have been
observed at certain fields in the range -1000 Oe < H < 1000 Oe, regardless of
the temperature considered. The field position of the magnetization jumps has
been studied at different temperatures, and their distribution can be described
by a Lorentzian curve.Comment: 6 pages, 3 figure
Dirac surface states, multiorbital dimerization and superconductivity in Nb- and Ta-based A15 compounds
Full text linkUsing first-principle calculations, we investigate the electronic,
topological and superconducting properties of NbX (X = Ge, Sn, Sb) and
TaY (Y = As, Sb, Bi) A15 compounds. We demonstrate that these compounds
host Dirac surface states which are related to a nontrivial Z topological
value. The spin-orbit coupling (SOC) splits the eightfold degenerate R point
close to the Fermi level enhancing the amplitude of the spin Hall conductance.
Indeed, despite the moderate spin-orbit of the Nb-compounds, a large spin Hall
effect is also obtained in NbGe and NbSn compounds. We show that the
Coulomb interaction opens the gap at the R point thus making more evident the
occurrence of Dirac surface states. We then investigate the superconducting
properties by determining the strength of the electron-phonon BCS coupling. The
evolution of the critical temperature is tracked down to the 2D limit
indicating a reduction of the transition temperature which mainly arises from
the suppression of the density of states at the Fermi level. Finally, we
propose a minimal tight-binding model based on three coupled
Su-Schrieffer-Heeger chains with t Ta- and Nb-orbitals reproducing the
spin-orbit splittings at the R point among the -bond bands in this class
of compounds. We separate the kinetic parameters in and -bonds,
in intradimer and interdimer hoppings and discuss their relevance for the
topological electronic structure. We point out that NbGe might represent a
Z topological metal with the highest superconducting temperature ever
recorded.Comment: 16 pages, 12 figures in main text, 3 figures in appendix, Paper
submitted to Physical Review
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