A5101430165- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Electronic and Structural Properties of Oxides
- Theoretical and Computational Physics
- Quantum many-body systems
- Quantum and electron transport phenomena
- Topological Materials and Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Superconducting Materials and Applications
- Spectroscopy and Quantum Chemical Studies
- ZnO doping and properties
- Parallel Computing and Optimization Techniques
- Quantum Computing Algorithms and Architecture
- Advanced Chemical Physics Studies
- Advanced Thermodynamics and Statistical Mechanics
- Quantum, superfluid, helium dynamics
- High-pressure geophysics and materials
- Solid-state spectroscopy and crystallography
- Distributed and Parallel Computing Systems
- Atomic and Subatomic Physics Research
- Inorganic Fluorides and Related Compounds
- Neural Networks and Reservoir Computing
Oak Ridge National Laboratory
2016-2025
Oak Ridge Associated Universities
2025
Florida International University
2024
Universidad Politécnica de Madrid
2023
Material Sciences (United States)
2018
Instituto de Investigaciones en Ciencia y Tecnología de Materiales
2011
National High Magnetic Field Laboratory
2002-2005
Florida State University
2002-2005
University of Tennessee at Knoxville
2004
Universidad de la República
1999
The one-orbital model for manganites with cooperative phonons and superexchange coupling ${J}_{\mathrm{AF}}$ is investigated via large-scale Monte Carlo simulations. results two orbitals are also briefly discussed. Focusing on the electron density $n=0.75$, a regime of competition between ferromagnetic metallic charge-ordered (CO) insulating states identified. In vicinity associated bicritical point, colossal magnetoresistance (CMR) effects observed. CMR development short-distance...
We propose a minimalist architecture for achieving various crystalline-symmetry-protected Majorana modes in an array of coupled quantum dots. Our framework is motivated by the recent experimental demonstrations two-site and three-site artificial Kitaev chains similar setup. find that introducing <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>π</a:mi></a:math>-phase domain wall chain leads to pair mirror-protected zero located at or near junction. Joining two <b:math...
Frequency-dependent correlations, such as the spectral function and dynamical structure factor, help illustrate condensed matter experiments. Within density matrix renormalization group (DMRG) framework, an accurate method for calculating functions directly in frequency is correction-vector method. The correction vector can be computed by solving a linear equation or minimizing functional. This paper proposes alternative to calculate vector: use Krylov-space approach. then studies accuracy...
Quantum computers hold the promise of solving certain problems that lie beyond reach conventional computers. Establishing this capability, especially for impactful and meaningful problems, remains a central challenge. One such problem is simulation nonequilibrium dynamics magnetic spin system quenched through quantum phase transition. State-of-the-art classical simulations demand resources grow exponentially with size. Here we show superconducting annealing processors can rapidly generate...
Phenomenological models for the antiferromagnetic (AF) versus $d$-wave superconductivity competition in cuprates are studied using conventional Monte Carlo techniques. The analysis suggests that may show a variety of different behaviors very underdoped regime: local coexistence or first-order transitions among competing orders, stripes, glassy states with nanoscale superconducting (SC) puddles. transition from AF to SC does not seem universal. In particular, state leads possibility...
The modulation of charge density and spin order in ${({\text{LaMnO}}_{3})}_{2n}/{({\text{SrMnO}}_{3})}_{n}$ $(n=1--4)$ superlattices is studied via Monte Carlo simulations the double-exchange model. $G$-type antiferromagnetic barriers ${\text{SrMnO}}_{3}$ regions with low are found to separate ferromagnetic ${\text{LaMnO}}_{3}$ layers high density. A metal-insulator transition increasing $n$ observed direction perpendicular interfaces. Our provide insight into how disorder-induced...
An undoped three-orbital spin-fermion model for the Fe-based superconductors is studied via Monte Carlo techniques in two-dimensional clusters. At low temperatures, magnetic and one-particle spectral properties are agreement with neutron photoemission experiments. Our main results resistance versus temperature curves that display same features observed BaFe(2)As(2) detwinned single crystals (under uniaxial stress), including a low-temperature anisotropy between two directions followed by...
Recent neutron scattering experiments addressing the magnetic state of two-leg ladder selenide compound BaFe$_2$Se$_3$ have unveiled a dominant spin arrangement involving ferromagnetically ordered 2$\times$2 iron-superblocks, that are antiferromagnetically coupled among them (the "block-AFM" state). Using electronic five-orbital Hubbard model, first principles techniques to calculate hopping amplitudes between irons, and real-space Hartree-Fock approximation handle many-body effects, here it...
The orbital-selective Mott phase of multiorbital Hubbard models has been extensively analyzed before using static and dynamical mean-field approximations. In parallel, the properties block states (antiferromagnetically coupled ferromagnetic spin clusters) in Fe-based superconductors have also much discussed. present effort uses numerically exact techniques one-dimensional systems to report observation within regime, connecting two seemingly independent areas research, providing analogies...
A lattice spin-fermion model for diluted magnetic semiconductors (DMS) is investigated numerically, improving on previously used mean-field approximations. Curie temperatures are obtained varying the Mn spin x and hole n densities, impurity-hole exchange J in units of hop-ping t. Optimal values found subtle intermediate regime between itinerant localized carriers. At large J/t, a "clustered" state observed above temperature ferromagnetism suppressed. Formal analogies DMS manganites discussed.
The recent discovery of superconductivity under high pressure in the two-leg ladder compound BaFe$_2$S$_3$ [H. Takahashi et al., Nature Materials 14, 1008 (2015)] opens a broad avenue research, because it represents first report pairing tendencies quasi one-dimensional iron-based critical temperature superconductor. Similarly as case cuprates, ladders and chains can be far more accurately studied using many-body techniques model Hamiltonians than their layered counterparts, particularly if...
Iron-based superconductors display a variety of magnetic phases originating in the competition between electronic, orbital, and spin degrees freedom. Previous theoretical investigations multi-orbital Hubbard model one dimension revealed existence an orbital-selective Mott phase (OSMP) with block order. Recent inelastic neutron scattering (INS) experiments on BaFe$_2$Se$_3$ ladder compound confirmed relevance block-OSMP. Moreover, powder INS spectrum reveled unexpected structure, containing...
Abstract Resonant Inelastic X-Ray Scattering (RIXS) experiments on the iron-based ladder BaFe 2 Se 3 unveiled an unexpected two-peak structure associated with local orbital ( dd ) excitations in a block-type antiferromagnetic phase. A mixed character between correlated band-like and localized was also reported. Here, we use density matrix renormalization group method to calculate momentum-resolved charge- orbital-dynamical response functions of multi-orbital Hubbard chain. Remarkably, our...
Using ab initio density functional theory and single-orbital Hubbard model calculations via the matrix renormalization group method, we systematically studied monolayer ${\mathrm{VOI}}_{2}$ with a $3{d}^{1}$ electronic configuration. Our phonon indicate that orthorhombic $Pmm2$ FE-II phase is most likely ground state, involving ferroelectric (FE) distortion along $a$ axis V-V dimerization $b$ axis. Specifically, ``pseudo Jahn-Teller'' effect caused by coupling between empty V (${d}_{xz/yz}$...
Abstract Motivated by the recent experimental realization of minimal Kitaev chains using quantum dots, we investigate Majorana zero modes (MZM) in Y -shape wires. We solve associated models analytically at sweet spot ( t h = Δ) and derive exact form MZM wave-functions this geometry. observed exotic multi-site MZMs located near junction center, on nearby edge sites each leg. This result is important for potential braiding Majoranas performance -junctions made from arrays dots. Furthermore,...
A model recently introduced for diluted magnetic semiconductors by Berciu and Bhatt (PRL 87, 107203 (2001)) is studied with a Monte Carlo technique, the results are compared to Hartree-Fock calculations. For doping rates close experimentally observed metal-insulator transition, picture dominated ferromagnetic droplets formed below T* scale emerges. The moments of these align as temperature lowered critical value Tc<T*. Our investigations provide temperatures considerably smaller than...
Large-scale Monte Carlo simulation results for the two-orbital model manganites, including Jahn-Teller lattice distortions, are presented here. At hole density x=1/4 and in vicinity of region competition between ferromagnetic metallic spin-charge-orbital ordered insulating phases, colossal magnetoresistance (CMR) phenomenon is observed with a ratio ∼10,000%. Our main result that this CMR transition found to be first order some portions phase diagram, agreement early from neutron scattering,...
Inelastic neutron scattering recently confirmed the theoretical prediction of a ↑↑↓↓-magnetic state along legs quasi-one-dimensional iron-based ladders in orbital-selective Mott phase (OSMP). We show here that electron doping OSMP induces whole class novel block states with variety periodicities beyond previously reported π/2 pattern. discuss magnetic diagram regime could be tested by neutrons once appropriate quasi-1D quantum materials dopings are identified.
We present the first open release of DCA++ project, a high-performance research software framework to solve quantum many-body problems with cutting edge cluster algorithms. implements dynamical approximation (DCA) and its DCA$^+$ extension continuous self-energy. The algorithms capture nonlocal correlations in strongly correlated electron systems, thereby giving insight into high-$T_c$ superconductivity. code's scalability allows efficient usage systems at all scales, from workstations...
An insulating ferromagnetic (FM) phase exists in the quasi-one-dimensional iron oxychalcogenide ${\mathrm{Ce}}_{2}{\mathrm{O}}_{2}{\mathrm{FeSe}}_{2}$, but its origin is unknown. To understand FM mechanism, here a systematic investigation of this material provided, analyzing competition between and antiferromagnetic tendencies interplay hoppings, Coulomb interactions, Hund's coupling, crystal-field splittings. Our intuitive analysis based on second-order perturbation theory shows that large...
We calculate the dynamical spin structure factor of generalized spin-$1/2$ compass chain using density matrix renormalization group. The model, also known as twisted Kitaev chain, was recently proposed to be relevant for description compound CoNb$_2$O$_6$. It features bond-dependent interactions and interpolates between an Ising a one-dimensional variant Kitaev's honeycomb model. factor, in turn, is found interpolate from gapped non-dispersive limit gapless with non-trivial continua limit....
The physics of manganites appears to be dominated by phase competition among ferromagnetic metallic and charge-ordered antiferromagnetic insulating states. Previous investigations [Burgy et al., Phys. Rev. Lett. 87, 277202 (2001)] have shown that quenched disorder is important smear the first-order transition between those competing states, induce nanoscale inhomogeneities produce colossal magnetoresistance effect. Recent studies [Motome 91, 167204 (2003)] provided further evidence crucial...