Temperature-dependent Correction Research Articles

Metallicity and its low-temperature behavior in dilute two-dimensional carrier systems

We theoretically consider the temperature-dependent and density dependent transport properties of semiconductor-based two-dimensional (2D) carrier systems within the RPA-Boltzmann (RPA, random-phase approximation) transport theory, taking into account realistic screened charged impurity scattering in the semiconductor. We derive a leading behavior in the transport property, which is exact in the strict 2D approximation and provides a zeroth-order explanation for the strength of metallicity in various 2D carrier systems. By carefully comparing the calculated full nonlinear temperature dependence of electronic resistivity at low temperatures with the corresponding asymptotic analytic form obtained in the ${T/T}_{F}\ensuremath{\rightarrow}0$ limit, both within the RPA screened charged impurity scattering theory, we critically discuss the applicability of the linear temperature-dependent correction to the low-temperature resistivity in 2D semiconductor structures. We find quite generally that for charged ionized impurity scattering screened by the electronic dielectric function (within RPA or its suitable generalizations including local-field corrections), the resistivity obeys the asymptotic linear form only in the extreme low-temperature limit of ${T/T}_{F}<~0.05.$ We point out the experimental implications of our findings and discuss in the context of the screening theory the relative strengths of metallicity in different 2D systems.

Effects of electron-electron and electron-phonon interactions in weakly disordered conductors and heterostructures

We investigate quantum corrections to the conductivity due to the interference of electron-electron (electron-phonon) scattering and elastic electron scattering from impurities and defects in weakly disordered conductors. The interference corrections are proportional to the Drude conductivity and have various temperature dependences. The electron-electron interaction results in a ${T}^{2}\mathrm{ln}T$ correction in bulk conductors. In a quasi-two-dimensional (quasi-2D) conductor, $d<{L}_{T}{=v}_{F}/T$ $(d$ is the thickness, and ${v}_{F}$ is the Fermi velocity), with 3D electron spectrum ${(p}_{F}d>1)$ this correction is linear in temperature and differs from that for 2D electrons [G. Zala et al., Phys. Rev. B 64, 214204 (2001)] by a numerical factor. In quasi-one-dimensional conductors with 3D and 2D electron spectra (a wire with radius $r<{L}_{T}$ and a strip with width $b<{L}_{T}),$ temperature-dependent corrections are proportional to $\mathrm{ln}T.$ The value and sign of the corrections depend on the strength of the electron-electron interaction in the triplet channel. The electron interaction via exchange of virtual phonons gives the ${T}^{2}\mathrm{ln}T$ correction. In bulk semiconductors the interaction of electrons with thermal phonons via the screened deformation potential results in a ${T}^{6}$ term and via unscreened deformation potential leads to a ${T}^{2}$ term. For a two-dimensional electron gas in heterostructures, the screened deformation potential gives rise to a ${T}^{4}$ term and the unscreened deformation potential leads to a ${T}^{2}\mathrm{ln}T$ term. At low temperatures the interference of electron-electron and electron-impurity scattering dominates in the temperature-dependent conductivity. At higher temperatures the conductivity is determined by the electron-phonon-impurity interference, which prevails over pure electron-phonon scattering in a wide temperature range, which extends with increasing disorder.

Light-front Schwinger model at finite temperature

We study the light-front Schwinger model at finite temperature following the recent proposal of Alves, Das, and Perez. We show that the calculations are carried out efficiently by working with the full propagator for the fermion, which also avoids subtleties that arise with light-front regularizations. We demonstrate this with the calculation of the zero temperature anomaly. We show that temperature dependent corrections to the anomaly vanish, consistent with the results from the calculations in conventional quantization. The gauge self-energy is seen to have the expected nonanalytic behavior at finite temperature, but does not quite coincide with the conventional results. However, the two structures are exactly the same on shell. We show that the temperature does not modify the bound state equations and that the fermion condensate has the same behavior at finite temperature as that obtained in conventional quantization.

A model for many-body interaction effects in open quantum dot systems

We discuss the influence of the electron–electron interaction on transportproperties of open quantum dot systems. Based on the idea of the Andersonmodel, we present interaction-induced temperature-dependent corrections to theconductance beyond the single-particle picture.

IMPURITIES IN A MAGNETIC-FIELD-INDUCED LUTTINGER LIQUID

We study the effect of dilute impurities on a system of interacting electrons subject to a quantizing magnetic field. For the case of point impurities, the calculation of the scattering cross section can be mapped onto a 1D problem of tunnelinng conductance through a barrier for interacting electrons. We find that the electron-electron interaction produces temperature-dependent corrections to the cross-section, and thus to the tensor of conductivities. Upon summation of the most diverging corrections in all orders of perturbation theory, a scaling behavior of the conductivities emerges. This behavior is similar to that of 1D Luttinger liquid. The scaling exponents depend on the magnetic field and are calculated explicitly in the weak-coupling limit. The limitations on the scaling behavior due to the formation of a charge-density wave are also discussed.

Finite temperature induced fermion number in the nonlinearσmodel in2+1dimensions

We compute the finite temperature induced fermion number for fermions coupled to a static nonlinear sigma model background in (2+1) dimensions, in the derivative expansion limit. While the zero temperature induced fermion number is well known to be topological (it is the winding number of the background), at finite temperature there is a temperature dependent correction that is nontopological -- this finite T correction is sensitive to the detailed shape of the background. At low temperature we resum the derivative expansion to all orders, and we consider explicit forms of the background as a CP^1 instanton or as a baby skyrmion.

Conductivity of a magnetic-field-induced Luttinger liquid

We study the effect of dilute impurities on a system of interacting electrons subject to a quantizing magnetic field. For the case of point impurities, the calculation of the scattering cross section can be mapped onto a 1D problem of tunneling conductance through a barrier for interacting electrons. We find that the electron–electron interaction produces temperature-dependent corrections to the cross-section, and thus to the tensor of conductivities. Upon summation of the most diverging corrections in all orders of the perturbation theory, a scaling behavior of the conductivities emerges. This behavior is similar to that of 1D Luttinger liquid. The scaling exponents depend on the magnetic field and are calculated explicitly in the weak-coupling limit. The limitations on the scaling behavior due to the formation of a charge-density wave are also discussed.

Corrections of Humidity Measurement Errors from the Vaisala RS80 Radiosonde—Application to TOGA COARE Data

A series of laboratory tests have been conducted on several different batches of Vaisala RS80 radiosondes to understand and develop methods to correct six humidity measurement errors, including chemical contamination, temperature dependence, basic calibration model, ground check, sensor aging, and sensor arm heating. The contamination and temperature-dependence (TD) errors dominate total errors. The chemical contamination error produces a dry bias, and is due to the occupation of binding sites in the sensor polymer by nonwater molecules emitted from the sonde packaging material. The magnitude of the dry bias depends on sensor polymer type (RS80-A and RS80-H), age of the sonde, relative humidity (RH), and temperature, and it exists throughout the troposphere. The contamination error generally increases with age and RH, and is larger for the RS80-H than the RS80-A. It is ∼2% and ∼10% at saturation for 1-yr-old RS80-A and RS80-H sondes, respectively. The TD error for the RS80-A results from an approximation of a linear function of temperature to the actual nonlinear temperature dependence of the sensor, and also introduces a dry bias. The TD error mainly exists at temperatures below −20°C, increases substantially with decreasing temperatures below −30°C, and is much larger for the RS80-A than the RS80-H. The RS80-A's TD correction (CTA) dominates the total correction at temperatures below −40°C and has a correction factor [CTA = (RH) (CTA_factor)] of 0.15, 0.75, and 2.3 at −40°, −60°, and −80°C, respectively. The correction methods are applied to 8129 Vaisala RS80 soundings collected during the Tropical Ocean and Global Atmosphere (TOGA) Coupled Ocean–Atmosphere Response Experiment (COARE) and are applicable to RS80 radiosonde data from other field experiments and historical and operational radiosonde datasets. The methods are validated by examining various summary plots of the TOGA COARE data and comparing them with other independent data. The corrections greatly improve the accuracy of the TOGA COARE radiosonde dataset. These correction methods have their own uncertainties and may not correct all errors in Vaisala RS80 humidity data. Analyses of these uncertainties are presented in the paper.

Fusion Mechanism in Superheavy Mass Region

58 Fe + 248 Cm were carried out. 2 The mass and the total kinetic energy distributions of fission fragments of these reactions were measured. In this paper, we focus on the fusion-fission process and try to reproduce the experimental data by using a fluctuation-dissipation model taking into account the competition between the fusion and quasi-fission. We estimate the fusion-fission cross section σCN as σCN = π¯ h 2 2µ0Ecm ∞ ∑=0 (2l+ 1)TlPCN , (1) where µ0 denotes the reduced mass in the entrance channel and Ecm denotes the incident energy in center-of-mass frame. Tl is the barrier penetration coefficient of the lth partial wave through the potential barrier. Tl is calculated with parabolic approximation of the combined Coulomb potential and proximity potential. PCN is the probability of forming a compound nucleus in the competition with quasi-fission. In this work, we employ the Langevin equation. 3 We adopt the three-dimensional nuclear deformation space with the twocenter parametrization. As the three collective parameters to be described by the Langevin equation, we treat z0 (distance between two potential centers), δ (deformation), and α (mass asymmetry of the colliding partner); α =( A1 − A2)/(A1 + A2), where A1 and A2 denote the mass number of target and projectile, respectively. Hydrodynamical inertia tensor is adopted with the Werner-Wheeler approximation for the velocity field, and the wall-and-window one-body dissipation is adopted for the dissipation tensor. For the purpose of the calibration of our calculation, firstly we analyze the fusion-fission cross section for the 48 Ca + 208 Pb reaction, where we can utilize the enough data of fusion-fission cross section. 2 The calculation results of the mass distribution of the fission fragments and the excitation function of the fusionfission cross section give a good agreement with the experimental data beyond the Bass barrier region. 4 Next, we present the analysis of the 48 Ca + 244 Pu reaction. We assume that both shapes of the target and the projectile are spherical at touching point of the colliding system. We also take into account the temperature dependent shell correction energy for the potential energy surface. 3, 4 For example, at T = 0, the potential energy surface in the reaction 48 Ca + 244 Pu is shown in Figure 1. z = δ = α = 0 corresponds to a spherical compound nucleus. The contact point in the reaction and saddle points are denoted by (+) point and (×) points, respectively. The shadow box denotes the fusion box which is defined as the inside of the fission saddle point, {z< 0.6, δ< 0.2, |α|< 0.25}. We can see

Development of an universal group contribution equation of state: I. Prediction of liquid densities for pure compounds with a volume translated Peng–Robinson equation of state

With a view to the development of an universal group contribution equation of state, the Peng–Robinson (PR) equation of state (EOS) has been modified to obtain a better description of saturated liquid densities for the pure compounds. A simple improved volume translation together with a temperature dependent volume correction deliver an accurate representation of this property near and far from the critical point for polar and non-polar substances. The fitted parameters have been generalized as a function of the critical compressibility factor. The results are compared with the results of the original PR and the Soave–Redlich–Kwong (SRK) EOS.

Vapor Phase Homogeneous Nucleation of Higher Alkanes: Dodecane, Hexadecane, and Octadecane. 1. Critical Supersaturation and Nucleation Rate Measurements

The critical supersaturations and isothermal homogeneous nucleation rates of dodecane, hexadecane, and octadecane vapors have been measured over wide temperature ranges (e.g., 285−340 K) using an upward thermal diffusion cloud chamber. Dodecane shows the best agreement between the experiment and the classical nucleation theory. Hexadecane and octadecane exhibit critical supersaturations lower than those predicted by the theory. All three compounds show increasing deviation from theory with decreasing temperature. This trend is also observed in the measured nucleation rates where the predictions of the theory at lower temperatures are shifted to much lower values compared to the experimental data. Temperature dependence correction factors to the calculated rates have been evaluated based on the experimental rates of the studied higher alkanes. The classical theory predicts the correct supersaturation dependence of the nucleation rates of these compounds. Analysis of the supersaturation dependence of the nu...

Fermi-liquid theory for anisotropic superconductors

This article develops a quantitative quasiparticle model of the low-temperature properties of d-wave superconductors which incorporates both Fermi-liquid effects and band-structure effects. The Fermi-liquid interaction effects are found to be classifiable into strong and negligible renormalizaton effects, for symmetric and antisymmetric combinations of the energies of $k\uparrow$ and $-k\downarrow$ quasiparticles, respectively. A particularly important conclusion is that the leading clean-limit temperature-dependent correction to the superfluid density is not renormalized by Fermi-liquid interactions, but is subject to a Fermi velocity (or mass) renormalization effect. This leads to difficulties in accounting for the penetration depth measurements with physically acceptable parameters, and hence reopens the question of the quantitative validity of the quasiparticle picture.

Homogeneous Nucleation of H2O and D2O in Comparison: The Isotope Effect

In the past century, the homogeneous nucleation of light water (H2O) has repeatedly been studied using various experimental techniques. Generally, the onset of nucleation was recorded, while less frequently, the actual nucleation rates were determined. In contrast, the nucleation of heavy water (D2O) has been examined only in a single instance with no nucleation rates measured. Here, we report the first nucleation rate study of D2O along with nucleation rate measurements for H2O, which we repeated for comparison under identical conditions. We find that the nucleation rates for H2O and D2O differ by a factor of 2500, if compared at the same respective vapor pressure pv and temperature T, whereas the comparison at the same supersaturation S shows an agreement within experimental scatter. Also, the numbers of molecules in the critical clusters, which are determined from the slopes of the ln J versus ln S curves, are nearly the same for both isotopic waters. A satisfactory agreement with previous nucleation rate measurements of H2O made by Viisanen et al. (Viisanen, Y.; Strey, R.; Reiss, H. J. Chem. Phys. 1993, 99, 4680; 2000, 112, 8205) is observed, if the onset supersaturations S0 at nucleation rates of J0 = 107 cm-3 s-1 are compared. Using the most recent expressions for temperature-dependent vapor pressures, we calculated surface tensions and densities predictions by the classical Becker−Döring nucleation theory. Around T = 240 K, the predictions quantitatively agree with the experimental data. However, as in the case of other systems (e.g., alcohols and alkanes), classical theory shows a stronger temperature dependence than experimentally observed. A temperature-dependent correction of the classical theory is developed which permits analytical calculation of nucleation rates as function of supersaturation and temperature over extended ranges.

Quantum chaos at finite temperature

We use the quantum action to study quantum chaos at finite temperature. We present a numerical study of a classically chaotic 2-D Hamiltonian system — harmonic oscillators with anharmonic coupling. We construct the quantum action non-perturbatively and find temperature-dependent quantum corrections in the action parameters. We compare Poincaré sections of the quantum action at finite temperature with those of the classical action.

Inclusion of temperature dependent shell corrections in Landau theory for hot rotating nuclei

Landau theory used for studying hot rotating nuclei usually uses zero temperature Strutinsky smoothed total energy for the temperature dependent shell corrections. This is replaced in this work by the temperature dependent Strutinsky smoothed free energy. Our results show that this replacement has only marginal effect for temperatures greater than 1 MeV but plays significant role at lower temperatures.

Characterization and Correction of Relative Humidity Measurements from Vaisala RS80-A Radiosondes at Cold Temperatures

Radiosonde relative humidity (RH) measurements are known to be unreliable at cold temperatures. This study characterizes radiosonde RH measurements from Vaisala RS80-A thin-film capacitive sensors in the temperature range 0° to −70°C. Sources of measurement error are identified, and two approaches for correcting the errors are presented. The corrections given in this paper apply only to the Vaisala RS80-A sensor, although the RS80-H sensor is briefly discussed for comparison. A temperature-dependent correction factor is derived from statistical analysis of simultaneous RH measurements from RS80-A radiosondes and the NOAA cryogenic frostpoint hygrometer. The mean RS80-A measurement error is shown to be a dry bias that increases with decreasing temperature, and the multiplicative correction factor is about 1.3 at −35°C, 1.6 at −50°C, 2.0 at −60°C, and 2.4 at −70°C. The fractional uncertainty in the mean of corrected measurements, when large datasets are considered statistically, increases from 0.06 at 0°C to 0.11 at −70°C. The fractional uncertainty for correcting an individual sounding is about ±0.2, which is larger because this statistical approach considers only the mean value of measurement errors that are not purely temperature dependent. The correction must not be used outside the temperature range 0° to −70°C, because it is a meaningless extrapolation of a polynomial curve fit. Laboratory measurements of sensor response conducted at Vaisala are used to characterize some of the individual sources of RS80-A measurement error. A correction factor is derived for the dominant RS80-A measurement error at cold temperatures: an inaccurate approximation for the sensor’s temperature dependence in the data processing algorithm. The correction factor for temperature-dependence error is about 1.1 at −35°C, 1.4 at −50°C, 1.8 at −60°C, and 2.5 at −70°C. Dependences and typical magnitudes are given for measurement errors that result from the temperature dependence of the sensor’s time constant, and from several smaller bias errors and random uncertainties.

Computer-Aided Series Expansion for Phonon Self-Energy

In this paper we discuss an algorithm for calculation of the temperature-dependent anharmonic correction to the phonon spectrum in atomic and molecular crystals. We show how the equation of motion method can be used to compute corrections of arbitrary perturbation order to the phonon self-energy. Complete analytical expressions up to order λ6 are obtained as an application of the method.

W-Boson mass operator in an external magnetic field at high temperatures

By the Schwinger proper-time method, the one-loop contribution to the W-boson mass operator is calculated in a constant magnetic field at high temperatures. The static limit is investigated. By averaging the mass operator over the physical states of a vector particle, the temperature-dependent radiative corrections to the W-boson energy spectrum are obtained at high magnetic fields (eH/M 2≫1) for various values of the spin projection onto the field direction. These corrections are found to be positive. In particular, the correction to the ground-state level stabilizes the W-boson vacuum state at high temperatures.

Two-dimensional vibrational spectroscopy. VI. Higher-order contributions to the two-dimensional vibrational response functions

The temperature-dependent first-order quantum correction contributions to the two-dimensional vibrational response functions, that are linearly proportional to ℏ, are theoretically investigated. By carrying out the semiclassical expansion of the nonlinear response function in the limit of weak anharmonicity of the potential-energy surface, seventy nine quantum correction terms are obtained. Although it is the cubic anharmonic couplings that were found to be important at the level of classical calculation of the associated nonlinear response functions, it is found that the quartic anharmonic terms can play a role as the quantum contributions. For a three-Brownian-oscillator model system, various numerical calculations of the 2D (two-dimensional) spectra are carried out to show how these quantum correction terms depend on temperature as well as on relative amplitudes of the quartic and cubic anharmonic coupling constants.

Response of a Fermi gas in a disordered system to a phonon flux

Phonon-induced conductivity (PIC) in a strongly elastically scattered two-dimensional electron gas in $\ensuremath{\delta}$-doped GaAs was studied using the heat-pulse technique. The results of phonoconductivity behavior with carrier temperature as well as magnetic field are presented. It was established that PIC is due to the influence of phonon flux on the temperature-dependent quantum corrections to conductivity through carrier heating. It was shown that the value of PIC is determined both by the absorbed nonequilibrium phonon power and the energy losses to lattice. The value of phonon flux energy absorbed by carriers was estimated from experiment.