808 research outputs found
Debye relaxation in high magnetic fields
Dielectric relaxation is universal in characterizing polar liquids and
solids, insulators, and semiconductors, and the theoretical models are well
developed. However, in high magnetic fields, previously unknown aspects of
dielectric relaxation can be revealed and exploited. Here, we report low
temperature dielectric relaxation measurements in lightly doped silicon in high
dc magnetic fields B both parallel and perpendicular to the applied ac electric
field E. For B//E, we observe a temperature and magnetic field dependent
dielectric dispersion e(w)characteristic of conventional Debye relaxation where
the free carrier concentration is dependent on thermal dopant ionization,
magnetic freeze-out, and/or magnetic localization effects. However, for BperpE,
anomalous dispersion emerges in e(w) with increasing magnetic field. It is
shown that the Debye formalism can be simply extended by adding the Lorentz
force to describe the general response of a dielectric in crossed magnetic and
electric fields. Moreover, we predict and observe a new transverse dielectric
response EH perp B perp E not previously described in magneto-dielectric
measurements. The new formalism allows the determination of the mobility and
the ability to discriminate between magnetic localization/freeze out and
Lorentz force effects in the magneto-dielectric response.Comment: 19 pages, 6 figure
Substitution Effect by Deuterated Donors on Superconductivity in -(BEDT-TTF)Cu[N(CN)]Br
We investigate the superconductivity in the deuterated BEDT-TTF molecular
substitution system
-[(h8-BEDT-TTF)(d8-BEDT-TTF)]Cu[N(CN)]Br, where h8
and d8 denote fully hydrogenated and deuterated molecules, respectively.
Systematic and wide range ( = 0 -- 1) substitution can control chemical
pressure finely near the Mott boundary, which results in the modification of
the superconductivity. After cooling slowly, the increase of
observed up to 0.1 is evidently caused by the chemical pressure
effect. Neither reduction of nor suppression of
superconducting volume fraction is found below 0.5. This demonstrates
that the effect of disorder by substitution is negligible in the present
system. With further increase of , both and superconducting
volume fraction start to decrease toward the values in = 1.Comment: J. Phys. Soc. Jp
A new scheme to optimize irrigation depth using a numerical model of crop response to irrigation and quantitative weather forecasts
Irrigation management can be improved by utilizing advances in numerical models of water flow in soils that can consider future rainfall by utilizing data from weather forecasts. Toward this end, we developed a numerical scheme to determine optimal irrigation depth on scheduled irrigation days based on a concept of virtual net income as a function of cumulative transpiration over each irrigation interval; this scheme combines a numerical model of crop response to irrigation and quantitative weather forecasts. To evaluate benefits, we compared crop growth and net income of this proposed scheme to those of an automated irrigation method using soil water sensors. Sweet potato (Ipomoea batatas (L.), cv. Kintoki) was grown in 2016 in a sandy field of the Arid Land Research Center, Tottori University, Japan under either a non-optimized automated irrigation or the proposed scheme. Under the proposed scheme, 18% less water was applied, yield increased by 19%, and net income was increased by 25% compared with the results of the automated irrigation system. In addition, soil water content simulated by the proposed scheme was in fair agreement with observed values. Thus, it was shown that the proposed scheme may enhance net income and be a viable alternative for determining irrigation depths
A bulk 2D Pauli Limited Superconductor
We present a nearly perfect Pauli-limited critical field phase diagram for
the anisotropic organic superconductor \-(ET)NH(SCN) when
the applied magnetic field is oriented parallel to the conducting layers. The
critical fields ({H_{c_2}) were found by use of penetration depth
measurements. Because {H_{c_2} is Pauli-limited, the size of the
superconducting energy gap can be calculated. The role of spin-orbit scattering
and many-body effects play a role in explaining our measurements.Comment: 4 pages, 5 figures. V5, corrections were made to the text, present
data was include
Experimental observation of Frohlich superconductivity in high magnetic fields
Resistivity and irreversible magnetisation data taken within the
high-magnetic-field CDWx phase of the quasi-two-dimensional organic metal
alpha-(BEDT-TTF)2KHg(SCN)4 are shown to be consistent with a field-induced
inhomogeneous superconducting phase. In-plane skin-depth measurements show that
the resistive transition on entering the CDWx phase is both isotropic and
representative of the bulk.Comment: ten pages, four figure
Critical State Behaviour in a Low Dimensional Metal Induced by Strong Magnetic Fields
We present the results of magnetotransport and magnetic torque measurements
on the alpha-(BEDT-TTF)2KHg(SCN)4 charge-transfer salt within the high magnetic
field phase, in magnetic fields extending to 33 T and temperatures as low as 27
mK. While the high magnetic field phase (at fields greater than ~ 23 T) is
expected, on theoretical grounds, to be either a modulated charge-density wave
phase or a charge/spin-density wave hybrid, the resistivity undergoes a
dramatic drop below ~ 3 K within the high magnetic field phase, falling in an
approximately exponential fashion at low temperatures, while the magnetic
torque exhibits pronounced hysteresis effects. This hysteresis, which occurs
over a broad range of fields, is both strongly temperature-dependent and has
several of the behavioural characteristics predicted by critical-state models
used to describe the pinning of vortices in type II superconductors in strong
magnetic fields. Thus, rather than exhibiting the usual behaviour expected for
a density wave ground state, both the transport and the magnetic properties of
alpha-(BEDT-TTF)2KHg(SCN)4, at high magnetic fields, closely resembles those of
a type II superconductor
Responses of ring widths and maximum densities of Larix gmelinii to climate on contrasting north- and south-facing slopes in central Siberia
The original publication is available at www.springerlink.com.ArticleEcological Research. 22(4):582-592 (2007)journal articl
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