Brownian survival and Lifshitz tail in perturbed lattice disorder

AbstractWe study discrete random Schrödinger operators via the supersymmetric formalism. We develop a cluster expansion that converges at both strong and weak disorder. We prove the exponential decay of the disorder-averaged Green’s function and the smoothness of the local density of states either at weak disorder and at energies in proximity of the unperturbed spectrum or at strong disorder and at any energy. As an application, we establish Lifshitz-tail-type estimates for the local density of states and thus localization at weak disorder.

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Lattice disorder effect on magnetic ordering of iron arsenides

Scientific Reports ◽

10.1038/s41598-019-56301-5 ◽

2019 ◽

Vol 9 (1) ◽

Author(s):

Athena S. Sefat ◽

Xiaoping P. Wang ◽

Yaohua Liu ◽

Qiang Zou ◽

Mimgming Fu ◽

...

Keyword(s):

Magnetic Coupling ◽

Magnetic Ordering ◽

Structural Features ◽

Lattice Parameter ◽

Chemical Compositions ◽

Lattice Disorder ◽

Local Lattice ◽

Higher Temperature ◽

Disordered Crystal ◽

Planar Strain

AbstractThis study investigates magnetic ordering temperature in nano- and mesoscale structural features in an iron arsenide. Although magnetic ground states in quantum materials can be theoretically predicted from known crystal structures and chemical compositions, the ordering temperature is harder to pinpoint due to potential local lattice variations that calculations may not account for. In this work we find surprisingly that a locally disordered material can exhibit a significantly larger Néel temperature (TN) than an ordered material of precisely the same chemical stoichiometry. Here, a EuFe2As2 crystal, which is a ‘122’ parent of iron arsenide superconductors, is found through synthesis to have ordering below TN = 195 K (for the locally disordered crystal) or TN = 175 K (for the ordered crystal). In the higher TN crystals, there are shorter planar Fe-Fe bonds [2.7692(2) Å vs. 2.7745(3) Å], a randomized in-plane defect structure, and diffuse scattering along the [00 L] crystallographic direction that manifests as a rather broad specific heat peak. For the lower TN crystals, the a-lattice parameter is larger and the in-plane microscopic structure shows defect ordering along the antiphase boundaries, giving a larger TN and a higher superconducting temperature (Tc) upon the application of pressure. First-principles calculations find a strong interaction between c-axis strain and interlayer magnetic coupling, but little impact of planar strain on the magnetic order. Neutron single-crystal diffraction shows that the low-temperature magnetic phase transition due to localized Eu moments is not lattice or disorder sensitive, unlike the higher-temperature Fe sublattice ordering. This study demonstrates a higher magnetic ordering point arising from local disorder in 122.

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ELECTRON MICROSCOPE OBSERVATION OF LATTICE DISORDER IN ION‐IMPLANTED SILICON

Applied Physics Letters ◽

10.1063/1.1653654 ◽

1971 ◽

Vol 18 (6) ◽

pp. 257-259 ◽

Cited By ~ 10

Author(s):

M. Bertolotti ◽

D. Sette ◽

L. Stagni ◽

G. Vitali

Keyword(s):

Electron Microscope ◽

Microscope Observation ◽

Electron Microscope Observation ◽

Lattice Disorder ◽

Ion Implanted

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Defect Structure of MEV Si Implantation in GaAs

MRS Proceedings ◽

10.1557/proc-126-183 ◽

1988 ◽

Vol 126 ◽

Cited By ~ 12

Author(s):

S.-Tong Lee ◽

G. Braunstein ◽

Samuel Chen

Keyword(s):

Free Surface ◽

Defect Structure ◽

Room Temperature ◽

Surface Region ◽

Peak Position ◽

Lattice Disorder ◽

Depth Profiles ◽

Trim Calculation ◽

Good Agreement

ABSTRACTThe defect and atomic profiles for MeV implantation of Si in GaAs were investigated using He++ channeling, TEM, and SIMS. Doses of 1–10 × 1015Si/cm2 at 1–3 MeV were used. MeV implantation at room temperature rendered only a small amount of lattice disorder in GaAs. Upon annealing at 400°C for 1 h or 800°C for 30 a, we observed a ‘defect-free’ surface region (- 1 μ for 3 MeV implant). Below this region, extensive secondary defects were formed in a band which was 0.7 μ wide and centered at 2 μ for 3 MeV implant. These defects were mostly dislocations lying in the [111] plane. SIMS depth profiles of Si implants showed the Si peak to be very close to the peak position of the defects. The experimental profiles of Si were compared to the TRIM calculation; generally good agreement existed among the peak positions.

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Thermal relaxation of lattice disorder in graphite induced by He+ irradiation

Solid State Communications ◽

10.1016/0038-1098(92)90234-z ◽

1992 ◽

Vol 82 (7) ◽

pp. 569-571 ◽

Cited By ~ 2

Author(s):

Kazutaka G. Nakamura ◽

Eiji Asari ◽

Masahiro Kitajima

Keyword(s):

Thermal Relaxation ◽

Lattice Disorder

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HPHT synthesis and enhanced TE performance of Te and Sn/Se elements binary-doped CoSb3

Functional Materials Letters ◽

10.1142/s1793604718501059 ◽

2019 ◽

Vol 12 (01) ◽

pp. 1850105 ◽

Cited By ~ 1

Author(s):

Hairui Sun ◽

Pin Lv ◽

Chao Wang ◽

Yunxian Liu ◽

Xiaopeng Jia ◽

...

Keyword(s):

Experimental Data ◽

Thermal Conductivity ◽

High Pressure ◽

High Temperature ◽

Seebeck Coefficient ◽

Grain Boundaries ◽

Preparation Methods ◽

Synthesis Time ◽

Lattice Disorder ◽

Positive Effect

A series of binary-doped CoSb3 with Te and Se/Sn bulk compounds Co4Sb[Formula: see text]TexSny/Sey ([Formula: see text] and 0.6, [Formula: see text] and 0.3), have been successfully prepared via a simple high pressure and high-temperature (HPHT) method. And, the influence of the doping elements on the microstructure of the samples synthesized under diverse pressures and the corresponding TE performance were studied in detail. Comparing with other preparation methods, the synthesis time of HPHT was acutely shortened. The obtained samples contain more grain boundaries, lattice disorder, dislocations and the possible “nanodot”, which have positive effect on reducing thermal conductivity. The experimental data indicate that the absolute values of Seebeck coefficient increases with pressure. What’s more, the thermal conductivities show a monotone decreasing trend as the synthesis pressure rises. The minimum value obtained is 1.93[Formula: see text]Wm[Formula: see text]K[Formula: see text] at normal temperature for Co4Sb[Formula: see text]Te[Formula: see text]Se[Formula: see text] prepared under 3[Formula: see text]GPa.

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Fractal aggregates of lanthanide-doped Y2O3 nanoparticles obtained by propellant synthesis

Journal of Materials Research ◽

10.1557/jmr.2001.0025 ◽

2001 ◽

Vol 16 (1) ◽

pp. 146-154 ◽

Cited By ~ 22

Author(s):

Stefano Polizzi ◽

Giuliano Fagherazzi ◽

Marino Battagliarin ◽

Marco Bettinelli ◽

Adolfo Speghini

Keyword(s):

Building Blocks ◽

Compositional Gradient ◽

Fractal Aggregates ◽

Scaling Properties ◽

X Ray ◽

Lattice Disorder ◽

Average Value ◽

X Ray Scattering ◽

20 Nm ◽

Ray Scattering

Y2-xLnxO3 (Ln 4 Ce, Pr, Nd, Eu, Gd, Ho, and Er) powders obtained by propellant synthesis have been characterized using small-angle x-ray scattering, wide-angle x-ray scattering, and transmission and scanning electron microscopy. All the samples showed a very porous, open microstructure with fractal scaling properties. The building blocks of the fractal aggregates are nanocrystallites of lanthanide-doped Y2O3, with variations in the cubic lattice constant proportional to the composition of the solid solution and to the lanthanide ionic radius. The particles had a narrow distribution of sizes with an average value in the 20–50 nm range. They are made of a core of 10–20 nm, consisting of almost perfectly ordered crystals and a “fuzzy” layer, characterized by either a growing lattice disorder or by a compositional gradient. From this dimension, up to at least 200 nm, the particle aggregate is a mass fractal with a fractal dimension, DMf, in the 1.6–2.0 range.

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