Electron dephasing in homogeneous and inhomogeneous indium tin oxide thin films

The electron dephasing processes in two-dimensional homogeneous and inhomogeneous indium tin oxide thin films have been investigated in a wide temperature range 0.3--90 K. We found that the small-energy-transfer electron-electron ($e$-$e$) scattering process dominated the dephasing from a few K to several tens K. At higher temperatures, a crossover to the large-energy-transfer $e$-$e$ scattering process was observed. Below about 1--2 K, the dephasing time $\tau_\varphi$ revealed a very weak temperature dependence, which intriguingly scaled approximately with the inverse of the electron diffusion constant $D$, i.e., $\tau_\varphi (T \approx 0.3 \, {\rm K}) \propto 1/D$. Theoretical implications of our results are discussed. The reason why the electron-phonon relaxation rate is negligibly weak in this low-carrier-concentration material is presented.Comment: 10 pages, 7 figure

Two-Channel Kondo Effects in Al/AlOx_{x}/Sc Planar Tunnel Junctions

We have measured the differential conductances $G(V,T)$ in several Al/AlO$_{x}$/Sc planar tunnel junctions between 2 and 35 K. As the temperature decreases to $\sim$ 16 K, the zero-bias conductance $G(0,T)$ crosses over from a standard $-$ln$T$ dependence to a novel $- \sqrt{T}$ dependence. Correspondingly, the finite bias conductance $G(V,T)$ reveals a two-channel Kondo scaling behavior between $\sim$ 4 and 16 K. The observed two-channel Kondo physics is ascribed to originating from a few localized spin-$\frac12$ Sc atoms situated slightly inside the AlO$_x$/Sc interface.Comment: 4 pages, 3 figures. Phys. Rev. B (accepted

Geochronology and Tectonic Significance of Middle Proterozoic Granitic Orthogneiss, North Qaidam HP/UHP Terrane, Western China

Amphibolite-facies para- and orthogneisses near Dulan, in the southeast part of the North Qaidam terrane, enclose minor ultra-high pressure (UHP) eclogite and peridotite. Field relations and coesite inclusions in zircons from paragneiss suggest that felsic, mafic, and ultramafic rocks all experienced UHP metamorphism and a common amphibolite-facies retrogression. Ion microprobe U–Pb and REE analyses of zircons from two granitic orthogneisses indicate magmatic crystallization at 927 ± Ma and 921 ± 7 Ma. Zircon rims in one of these samples yield younger ages (397–618 Ma) compatible with partial zircon recrystallization during in-situ Ordovician-Silurian eclogite-facies metamorphism previously determined from eclogite and paragneiss in this area. The similarity between a 2496 ± 18 Ma xenocrystic core and 2.4–2.5 Ga zircon cores in the surrounding paragneiss suggests that the granites intruded the sediments or that the granite is a melt of the older basement which supplied detritus to the sediments. The magmatic ages of the granitic orthogneisses are similar to 920–930 Ma ages of (meta)granitoids described further northwest in the North Qaidam terrane and its correlative west of the Altyn Tagh fault, suggesting that these areas formed a coherent block prior to widespread Mid Proterozoic granitic magmatism. Included here is the post-print copy of this article. The final publication is available at Springer via http://dx.doi.org/10.1007/s00710-006-0149-1

Timing of eclogite-facies metamorphism of the Chuacús complex, Central Guatemala: Record of Late Cretaceous continental subduction of North America's sialic basement

A Late Cretaceous collision of the southernmost portion of the North American continental margin with an undetermined southern block was first established based on the sedimentation history of the plate's supracrustal cover, which is overthrust by harzburgite-dominated nappes of the Guatemala Suture Complex. The collision is also well registered in the metamorphic evolution of continental eclogites of the Chuacús complex, a geologic unit that represents Mesoproterozoic–Triassic sialic basement of North America at the boundary with the Caribbean plate. Garnet–clinopyroxene–phengite thermobarometry of eclogites hosted in Chuacús gneisses indicates near ultra-high-pressure conditions to ~ 700 °C and ~ 2.1–2.4 GPa. SHRIMP-RG U–Pb dating of eclogite metamorphic zircon yielded a 75.5 ± 2 Ma age (95% confidence level). Chondrite-normalized rare-earth element patterns of zircon lack Eu anomalies and show depletions in heavy rare earths, consistent with zircon growing in a plagioclase-free, garnet-rich, eclogite-facies assemblage. Additionally, a Sm–Nd clinopyroxene-two garnet–whole rock isochron from an eclogite band yielded a less precise but consistent age of 77 ± 13 Ma. The above features imply subduction to > 60 km depth of at least a portion of the North American sialic basement during Late Cretaceous collision. The Chuacús complex was overprinted by an amphibolite-facies event. For instance, mafic high-pressure paragneiss contains symplectite, resorbed garnet, and amphibole + plagioclase poikiloblasts. Zircon rims from the paragneiss sample show rare-earth patterns consistent with plagioclase growth and garnet breakdown. Their 74.5 ± 3.5 Ma SHRIMP-RG U–Pb age is therefore interpreted as the time of retrogression, which is consistent with previously published results. Within error, the ages of the eclogite-facies event and the amphibolite-facies retrogression are equivalent. Thus exhumation of the Chuacús slab from mantle to mid-crustal depth was quick, taking few million years. During exhumation, partial melting of Chuacús gneisses generated ubiquitous pegmatites. One of the pegmatites intruded the North Motagua mélange, which is a serpentinite-rich subduction complex of the Guatemala Suture Complex containing Early Cretaceous oceanic eclogites. U–Pb, Rb–Sr, and K–Ar ages of the pegmatite range ~ 76–66 Ma. Thus initial juxtaposition of continental and oceanic high-pressure belts of the Guatemala Suture Complex predates Tertiary–present strike-slip faulting between the North-American and Caribbean plates

Thermodynamic properties and structural stability of thorium dioxide

Using density functional theory (DFT) calculations, we have systematically investigated the thermodynamic properties and structural stabilities of thorium dioxide (ThO$_2$). Based on the calculated phonon dispersion curves, we calculate the thermal expansion coefficient, bulk modulus, and heat capacities at different temperatures for ThO$_2$ under the quasi-harmonic approximation. All the results are in good agreement with corresponding experiments proving the validity of our methods. Our theoretical studies can help people more clearly understand the thermodynamic behaviors of ThO$_2$ at different temperatures. In addition, we have also studied possible defect formations and diffusion behaviors of helium in ThO$_2$, to discuss its structural stability. It is found that in intrinsic ThO$_2$ without any Fermi energy shifts, the interstitial Th$_i^{4+}$ defect other than oxygen or thorium vacancies, interstitial oxygen, and any kinds of Frenkel pairs, is most probable to form with an energy release of 1.74 eV. However, after upshifting the Fermi energy, the formation of the other defects also becomes possible. For helium diffusion, we find that only through the thorium vacancy can it happen with the small energy barrier of 0.52 eV. Otherwise, helium atoms can hardly incorporate or diffuse in ThO$_2$. Our results indicate that people should prevent upshifts of the Fermi energy of ThO$_2$ to avoid the formation of thorium vacancies and so as to prevent helium caused damages.Comment: 11 pages, 11 figure

Measurement of inner wall limiter SOL widths in KSTAR tokamak

https://doi.org/10.1016/j.nme.2016.12.001.Scrape-off layer (SOL) widths λq are presented from the KSTAR tokamak using fast reciprocating Langmuir probe assembly (FRLPA) measurements at the outboard mid-plane (OMP) and the infra-Red (IR) thermography at inboard limiter tiles in moderately elongated (κ = 1.45 – 1.55) L-mode inner wall-limited (IWL) plasmas under experimental conditions such as BT = 2.0 T, PNBI = 1.4 – 1.5 MW, line averaged densities 2.5 – 5.1 × 1019 m−3) and plasma current Ip = 0.4 − 0.7 MA. There is clear evidence for a double exponential structure in q||(r) from the FRLPA such that, for example at Ip = 0.6 MA, a narrow feature, λq,near (=3.5 mm) is found close to the LFCS, followed by a broader width, λq,main (=57.0 mm). Double exponential profiles (λq,near = 1.5 – 2.8 mm, λq,main = 17.0 – 35.0 mm) can be also observed in the IR heat flux mapped to the OMP throughout the range of Ip investigated. In addition, analysis of SOL turbulence statistics obtained with the FRLPA shows high relative fluctuation levels and positively skewed distributions in electron temperature and ion particle flux across the SOL, with both properties increasing for longer distance from the LCFS, as often previously observed in the tokamaks. Interestingly, the fluctuation character expressed in terms of spectral distributions remains unchanged in passing from the narrow to the broad SOL heat flux channel

Homeownership and Wealth in Switzerland and Germany

Property wealth represents the most important wealth component in nearly all OECD countries. Homeownership is linked to wealth accumulation in several ways: Wealthier households are more likely to buy a house or apartment, home owners tend to save more and rising house values typically yield higher returns than money in a bank account. Moreover, owners can borrow on a mortgage to finance, e.g., the formation of an enterprise or other economic activities. At the aggregate level, these relations can explain why countries with low rates of homeownership tend to have a high wealth inequality. This paper looks at wealth and homeownership in Germany and Switzerland. These countries show the lowest proportion of owner-occupiers in Europe and a high wealth inequality. We analyse to what extent this high inequality can be explained by homeownership status. In the first part of this contribution, we review explanations for the low share of owner-occupiers in the two countries. In the second part, we analyse wealth and homeownership empirically using data of the SHP and the German Socio-Economic Panel (SOEP) from 2012. We make use of decomposition methods to analyse how renter and owner households differ in wealth levels and wealth inequality

Development of the upgraded single crystal dispersion interferometer (SCDI-U) and its first measurements of the line integrated electron densities in KSTAR during shattered pellet injections

Dispersion interferometers (DI) are widely used to measure line integrated electron densities in many fusion devices. A recent development of a heterodyne single crystal DI (SCDI) with a laser wavelength of 1064 nm (Lee et al 2021 Rev. Sci. Instrum. 92 033536) allows an easier and simpler optical setup by using only one, instead of two, nonlinear crystal. It is found that the reported heterodyne SCDI with an acoustic-optical modulator (AOM) has different beam paths between the frequency-shifted, via the AOM, fundamental and second harmonics which act as the reference beams. Such a separation of the reference beams inevitably produces non-removable phase shifts associated with mechanical vibrations, resulting in a reduction of the removing efficiency of the mechanical vibrations that DI systems can provide. By utilizing the fact that the diffraction angle due to the AOM is inversely proportional to the frequency of the laser beam and linearly proportional to an order of the frequency-shift, the SCDI-Upgrade (SCDI-U), which has complete overlap of the optical paths for both probing and reference beams from the laser source to the detectors, is proposed in this work. Its first measurements in KSTAR during shattered pellet injections are reported, and results obtained by the SCDI-U are compared with those from the existing two-color interferometer (TCI) in KSTAR. It is found that the SCDI-U measures the electron density more reliably during such an abrupt and large density change than the TCI does. Qualitative analyses on the effects of different injection schemes of the shattered pellets and possible application of the SCDI-U for ITER are also discussed