25,198 research outputs found
Optical properties of in the normal state
We present the optical reflectance and conductivity spectra for non-oxide
antiperovskite superconductor at different temperatures. The
reflectance drops gradually over a large energy scale up to 33,000 cm,
with the presence of several wiggles. The reflectance has slight temperature
dependence at low frequency but becomes temperature independent at high
frequency. The optical conductivity shows a Drude response at low frequencies
and four broad absorption features in the frequency range from 600 to
33,000 . We illustrate that those features can be well understood from
the intra- and interband transitions between different components of Ni 3d
bands which are hybridized with C 2p bands. There is a good agreement between
our experimental data and the first-principle band structure calculations.Comment: 4 pages, to be published in Phys. Rev.
The upper critical field and its anisotropy in LiFeAs
The upper critical field of LiFeAs single crystals has
been determined by measuring the electrical resistivity using the facilities of
pulsed magnetic field at Los Alamos. We found that of LiFeAs
shows a moderate anisotropy among the layered iron-based superconductors; its
anisotropic parameter monotonically decreases with decreasing
temperature and approaches as . The upper
critical field reaches 15T () and 24.2T () at
1.4K, which value is much smaller than other iron-based high
superconductors. The temperature dependence of can be
described by the Werthamer-Helfand-Hohenberg (WHH) method, showing orbitally
and (likely) spin-paramagnetically limited upper critical field for and , respectively.Comment: 5 pages,5 figure
Controllable coupling between a nanomechanical resonator and a coplanar-waveguide resonator via a superconducting flux qubit
We study a tripartite quantum system consisting of a coplanar-waveguide (CPW)
resonator and a nanomechanical resonator (NAMR) connected by a flux qubit,
where the flux qubit has a large detuning from both resonators. By a unitray
transformation and a second-order approximation, we obtain a strong and
controllable (i.e., magnetic-field-dependent) effective coupling between the
NAMR and the CPW resonator. Due to the strong coupling, vacuum Rabi splitting
can be observed from the voltage-fluctuation spectrum of the CPW resonator. We
further study the properties of single photon transport as inferred from the
reflectance or equivalently the transmittance. We show that the reflectance and
the corresponding phase shift spectra both exhibit doublet of narrow spectral
features due to vacuum Rabi splitting. By tuning the external magnetic field,
the reflectance and the phase shift can be varied from 0 to 1 and to
, respectively. The results indicate that this hybrid quantum system can
act as a quantum router.Comment: 8 pages, 6 figure
Field study on the influence of spatial and environmental characteristics on the evaluation of subjective loudness and acoustic comfort in underground shopping streets
A large-scale measurement and subjective survey was undertaken in five underground
shopping streets to determine the influence of spatial and environmental characteristics on
users’ subjective loudness and acoustic comfort. The analysis on the spatial characteristics
shows that the subjective loudness is higher in “street type” than in “square type”
underground shopping streets when the equivalent continuous A-weighted sound pressure
level (LAeq) is relatively high (75 dBA). Acoustic comfort is higher in “square type” than in
“street type” underground shopping streets where LAeq is relatively low (55 dBA).
Considering spatial functions, it is found that acoustic comfort is higher in a dining area than
in a shopping area. In terms of environmental characteristics where air temperature, relative
humidity, luminance and visual aspect were considered, the subjective loudness is influenced
by humidity and luminance, with correlation coefficients of 0.10 to 0.30. The evaluation of
acoustic comfort is influenced by air temperature, humidity, and luminance, with correlation
coefficients of 0.1 to 0.4. There are significant correlations between the evaluation of
environmental factors and subjective loudness, as well as, acoustic comfort. The correlation
coefficients are 0.1 to 0.5. Moreover, respondents’ attitude to sound environment could
influence their evaluation of subjective loudness and acoustic comfort
Effects of individual sound sources on the subjective loudness and acoustic comfort in underground shopping streets
Previous studies have demonstrated that human evaluation of subjective loudness and
acoustic comfort depends on a series of factors in a particular situation rather than only on
sound pressure levels. In the present study, a large-scale subjective survey has been
undertaken on underground shopping streets in Harbin, China, to determine how individual
sound sources influence subjective loudness and acoustic comfort evaluation. Based on the
analysis of case study results, it has been shown that all individual sound sources can increase
subjective loudness to a certain degree. However, their levels of influence on acoustic comfort
are different. Background music and the public address system can increase acoustic comfort,
with a mean difference of 0.18 to 0.32 and 0.21 to 0.27, respectively, where a five-point
bipolar category scale is used. Music from shops and vendor shouts can decrease acoustic
comfort, with a mean difference of -0.11 to -0.38 and -0.39 to -0.62, respectively. The
feasibility of improving acoustic comfort by changing certain sound sources is thus
demonstrated
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