A5049299387- Magnetic properties of thin films
- Advanced Chemical Physics Studies
- Atomic and Molecular Physics
- Quantum and electron transport phenomena
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- Topological Materials and Phenomena
- Graphene research and applications
- Force Microscopy Techniques and Applications
- Magneto-Optical Properties and Applications
- Advanced Electron Microscopy Techniques and Applications
- Superconductivity in MgB2 and Alloys
- Diamond and Carbon-based Materials Research
- Nuclear Materials and Properties
- Inorganic Fluorides and Related Compounds
- Nuclear physics research studies
- Cold Atom Physics and Bose-Einstein Condensates
- 2D Materials and Applications
- Advanced Physical and Chemical Molecular Interactions
- Electronic and Structural Properties of Oxides
- Quantum, superfluid, helium dynamics
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Spectroscopy and Quantum Chemical Studies
- Theoretical and Computational Physics
Uppsala University
2014-2024
Colorado State University
2020
Autonomous University of Campeche
2020
Universidad Politecnica del Estado de Morelos
2016
University of Córdoba
2008-2011
Universidad de Granada
2006-2010
Argonne National Laboratory
1970-1971
Unveiling new topological phases of matter is one the current objectives in condensed physics. Recent experimental discoveries Dirac and Weyl semimetals prompt to search for other exotic matter. Here we present a systematic angle-resolved photoemission spectroscopy (ARPES) study ZrSiS, prime nodal semimetal candidate. Our wider Brillouin zone (BZ) mapping shows multiple Fermi surface pockets such as diamond-shaped surface, ellipsoidal-shaped small electron pocket encircling at center (G)...
The discovery of a topological nodal-line (TNL) semimetal phase in ZrSiS has invigorated the study other members this family. Here, we present comparative electronic structure ZrSiX (where X = S, Se, Te) using angle-resolved photoemission spectroscopy (ARPES) and first-principles calculations. Our ARPES studies show that overall materials comprises diamond-shaped Fermi pocket, nearly elliptical-shaped small electron pocket encircling zone center ($\Gamma$) point, M point Brillouin zone,...
Hartree–Fock interaction energy curves have been calculated for the X 2Σ+, A 2Π, and B 2Σ+ states of neutral LiHe NaHe as well ground state 1Σ+ ions over a range distances from 3 to 10 a.u. Since it is intended apply these results scattering problems, variation dipole quadrupole moments electronic transition probabilities with internuclear distance were also obtained. Both Slater-type functions Gaussian-type used variational trial intention gauging efficacy Gaussian basis. Except situations...
Ultrafast heating of a ferrimagnet’s crystal lattice leads to new state matter with hot spins yet unchanged magnetization.
Ultrafast laser excitation of a metal causes correlated, highly nonequilibrium dynamics electronic and ionic degrees freedom, which are, however, only poorly captured by the widely used two-temperature model. Here we develop an out-of-equilibrium theory that captures full dynamic evolution phononic populations provides microscopic description transfer energy delivered optically into electrons to lattice. All essential processes, such as electron-phonon phonon-phonon interactions are taken...
Topological Dirac semimetals with accidental band touching between conduction and valence bands protected by time reversal inversion symmetry are at the frontier of modern condensed matter research. Theoretically one can get Weyl and/or nodal-line breaking either them. Most discovered topological nonmagnetic i.e respect symmetry. Here we report experimental observation a semi metallic state in GdSbTe using angle-resolved photoemission spectroscopy. Our systematic study reveals detailed...
Abstract A material’s magnetic state and its dynamics are of great fundamental research interest also at the core a wide plethora modern technologies. However, reliable access to magnetization in materials devices on technologically relevant ultrafast timescale, under realistic device-operation conditions, remains challenge. Here, we demonstrate method terahertz (THz) magnetometry, which gives direct (sub-)picosecond even encapsulated or contact-free fashion, fully calibrated manner, ambient...
We investigate femtosecond spin injection from an optically excited Ni top layer into Au bottom using time-resolved complex magneto-optical Kerr effect (C-MOKE) measurements. Employing the C-MOKE formalism, we are able to follow layer-resolved demagnetization in and simultaneous adjacent film, both occurring within $\ensuremath{\sim}40\phantom{\rule{0.16em}{0ex}}\mathrm{fs}$. confirm ballistic diffusive propagation of transfer process with ab initio theory superdiffusive transport...
Abstract Magnetostriction, the strain induced by a change in magnetization, is universal effect magnetic materials. Owing to difficulty unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how source of magnetostriction—the underlying magnetoelastic stress—can be separated time domain, opening door for an atomistic understanding. X-ray and electron diffraction are used separate sub-picosecond spin lattice responses FePt nanoparticles. Following...
We develop the anisotropic Eliashberg framework for superconductivity in presence of an applied magnetic field. Using as input ab initio calculated electron and phonon band structures electron-phonon coupling, we solve self-consistently equations archetypal superconductor ${\mathrm{MgB}}_{2}$. find two self-consistent solutions, time-even two-band superconductivity, well unconventional time-odd $s$-wave spin triplet emerging with provide full momentum, frequency, spin-resolved dependence...
Femtosecond laser excitation of solid-state systems creates non-equilibrium hot electrons that cool down by transferring their energy to other degrees freedom and ultimately lattice vibrations the solid. By combining ab initio calculations with ultrafast diffuse electron scattering we gain a detailed understanding complex transfer between phonons in laser-excited Ni metal. Our experimental results show wavevector resolved population dynamics phonon modes is distinctly different throughout...
We use femtosecond time-resolved hard x-ray scattering to detect coherent acoustic phonons excited during ultrafast laser demagnetization of bcc Fe films. determine the lattice strain propagating through film analysis oscillations in signal as a function momentum transfer. The width wavefront is ~100 fs, similar timescales. First-principles calculations show that high-frequency Fourier components strain, which give rise sharp wavefront, could part originate from non-thermal dynamics not...
Ultrashort light pulses can selectively excite charges, spins, and phonons in materials, providing a powerful approach for manipulating their properties. Here we use femtosecond laser to coherently manipulate the electron phonon distributions, couplings, charge-density wave (CDW) material 1T-TaSe2 After exciting with pulse, fast spatial smearing of laser-excited electrons launches coherent lattice breathing mode, which turn modulates temperature. This finding is contrast all previous...
The experimental discovery of the topological Dirac semimetal establishes a platform to search for various exotic quantum phases in real materials. ZrSiS-type materials have recently emerged as nodal-line semimetals where gapped Dirac-like surface states are observed. Here, we present systematic angle-resolved photoemission spectroscopy (ARPES) study ZrGeTe, nonsymmorphic symmetry protected semimetal. We observe two gapless at same $\overline{X}$ point Brillouin zone. Our theoretical...
Magnetic nanoparticles such as FePt in the L1 0 phase are bedrock of our current data storage technology. As grains become smaller to keep up with technological demands, superparamagnetic limit calls for materials higher magnetocrystalline anisotropy. This, turn, reduces magnetic exchange length just a few nanometers, enabling structures be induced within nanoparticles. Here, we describe existence spin-wave solitons, dynamic localized bound states excitations, We show time-resolved x-ray...
Identifying the microscopic nature of non-equilibrium energy transfer mechanisms among electronic, spin, and lattice degrees freedom is central to understanding ultrafast phenomena such as manipulating magnetism on femtosecond timescale. Here, we use time- angle-resolved photoemission spectroscopy go beyond often-used ensemble-averaged view dynamics in terms quasiparticle temperature evolutions. We show for ferromagnetic Ni that electron spin display pronounced variations with momentum,...
Femtosecond laser-induced magnetization dynamics has recently been related to superdiffusive spin transport. With the aim accurately compute superdiffusion in complex geometries of layered heterostructures and free standing layers, we develop here a dedicated numerical scheme. We introduce discretization technique solve equation numerically on time space grid. The scheme facilitates an explicit treatment total reflection at vacuum-material surfaces as well partial reflections interfaces...
In the safety case for geological disposal of nuclear waste, release radioactivity from repository is controlled by dissolution spent fuel in groundwater. There remain several uncertainties associated with understanding dissolution, including contribution energetically reactive surface sites to rate. this study, we investigate how features influence rate synthetic CeO2 and ThO2, analogues that approximate as closely possible microstructure characteristics fuel-grade UO2 but are not sensitive...
The dynamics of electrons and phonons in metals upon laser excitation are often described by the two-temperature model, which assumes that both subsystems individually thermal equilibrium. However, recent experiments show this description is not sufficient to describe out-of-equilibrium on ultrashort timescales. Here, assuming a thermalized electronic system, we extend apply parameter-free microscopic model ultrafast laser-induced phonon electron temperature various metallic systems such as...
Utilizing first-principle simulations [based on density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U)], we develop a model to explain the experimental stability in solution of materials having fluorite structure, such as CaF2 and CeO2. It is shown that surface mainly dependent its atomic structure presence sites where atoms are deficiently bonded. Using reference planes surfaces with low formation energies, viz., (111), (100), (110), our results reveal relation...
Using first-principles simulations, we study the temperature- and pressure-dependent adsorption reaction of water on flat (111) (211) (221) stepped surfaces uranium dioxide. Our calculations are based density functional theory (DFT) corrected for on-site Coulomb interactions (DFT+U) describing chemical interaction with UO2, in combination ab initio molecular dynamics simulations to capture temperature dependence reaction. We compute pressure–temperature phase diagrams establish thermodynamic...