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We have performed a full self-consistent many-body study, within the framework of the random-phase approximation, on the intrinsic bistability in double-barrier resonant-tunneling structures. We found that the exchange-correlation effect can suppress the bistability which may be produced by the electrostatic feedback to the potential by the charge accumulated in the quantum well. Our self-consistent numerical results explain the existing contradiction between the affirmative theoretical prediction and the negative experimental observation on the occurrence of bistability in certain samples.

An analytical expression for shot noise in a correlated sequential tunneling current has been derived by solving the master equation exactly, with the Pauli correlation as a special case. Our theory is applied to the Coulomb-blockade single-electron tunneling system with two tunnel junctions. Given capacitances and resistances of the system, the temperature dependence and the bias-voltage dependence of the noise spectrum in the entire range of frequency have been analyzed in detail. We have demonstrated that the noise spectrum is more sensitive to the bias voltage than is the current itself to the voltage. Therefore, noise spectroscopy is a much more accurate tool to investigate the correlation in tunneling transport through ever smaller multiple-junction structures

The theory of inelastic electron resonant tunneling through a double-barrier nanostructure is extended to establish a theory of phonon-assisted resonant magnetotunneling when a magnetic field is applied parallel to the tunneling current. At higher temperatures we have discovered an interesting characteristic oscillation of the width and height of the main peak in the I-Y curve when the ratio ω 0 /ω c changes between integer (double resonant) and half integer (single resonant), where ω 0 is the LO phonon frequency and ω c is the cyclotron frequency in the well. If confirmed experimentally, our theoretical prediction provides an additional method to determine the electronic effective mass in the well

We have performed a detailed calculation of the I–V characteristic of a GaAs/Al x Ga 1−x As double barrier structure, with special emphasis on the phonon replica. For commonly used experimental samples (x≃0.3–0.4), the interface-like phonon modes produced by alloying and localized in barriers near the interfaces give the dominating contribution to the phonon replica. Our calculated I–V curves for samples of both symmetric and asymmetric barriers with or without bistability agree extremely well with experimental observations.

An analytical expression for shot noises in a correlated sequential tunneling current has been derived by solving the Master equation exactly. The existing result for the simplest case of Pauli correlation is easily reproduced. Our theory is applied to the Coulomb blockade single-electron tunneling system with two tunnel junctions. Given capacitances and resistances of the system, both the suppressed zero-frequency shot noise and the entire finite-frequency noise spectrum are obtained, which are much more complicated than the simplest Pauli correlation case. Our theoretical predictions, after being confirmed experimentally, will introduce the noise spectroscopy as a tool to investigate correlated tunneling current.

The lifetime τ e of an electron occupying the quasibound state in an Al x Ga 1-x As/GaAs doublebarrier structure has been calculated with both the tunneling Hamiltonian approach and the complex eigenvalue method. It is found that τ e is dominated by the barrier width, but is insensitive to the well width and the bias. We have also investigated the effect of the electron-LO-phonon interaction on the dynamics of the electron in the quasibound state

The inelastic scattering effect on electron tunneling through a double-barrier resonant tunneling device has been studied with a cumulant expansion on the electron transmission probability and the I-V characteristics using the Frohlich Hamiltonian which allows electron recoil enhances the incoherence process and so broadens the phonon replica, which is also shifted towards the main peak

We propose an iterative procedure to solve the linearized Gorkov equation and calculate the superconducting critical temperature of superconductor-normal metal superlattice in the whole region of layer thickness. We also give a discussion of the validity range of the local approximation made on the proximity effect of SN superlattice.

In the satellite remote sensing the resolution of the satellite image is always a restriction on the obtaining information and it is impossible that the resolution of pixel is unlimitedly raised. In the infrared region, the pixel values in a uniform picture element isn't effected by the resolution of pixel, but it is another case to some non- uniform picture elements. Each pixel value corresponds to the integration by the radiant excitance of the earth's surface inside of the pixel and is associated with not only the area of same radiation temperature but also the value of radiation temperature inside of the element. In this paper, the relationship between the pixel values and the area of same radiation temperature as well as the value of radiation temperature inside of the pixel was presented. A new train of ideas was given for the obtaining more information by today's resolution of pixel. With the help of this result, the monitor of some natural calamities (for example, the forest fire, the flood, the plant diseases and insect pests, etc.) will become much timely and they could be controlled as soon as possible.

We have studied the current I(\ensuremath{\omega},t)=${\mathit{I}}_{0}$(\ensuremath{\omega})+${\mathit{I}}_{1}$(\ensuremath{\omega},t) through a double-barrier resonant tunneling system (DBRTS) under a dc-ac bias. With a 2D emitter, the ac shift of the resonant level can be determined from ${\mathit{I}}_{0}$(\ensuremath{\omega}), and the intrinsic inductance of a DBRTS is unambiguously defined from ${\mathit{I}}_{1}$(\ensuremath{\omega},t). For presently available DBRT diodes under maximum operation frequency, the photon replica cannot be observed in the I-V curve. With a 3D emitter, a quantum-equivalent-circuit model can be constructed to calculate the maximum operation frequency of the diode, with good agreement with the measured value.

We consider electrons tunneling through a double-barrier resonant-tunneling structure (DBRTS) and interacting with a defect which has internal degrees of freedom. Usually such a defect has two (or more) metastable configurations and can switch between them due to its interaction with a thermal bath. Interaction between the tunneling electron and the dynamic defect creates a noisy environment surrounding the DBRTS, and leads to fluctuations in time of the resonant level. Such fluctuations result in inelastic tunneling and low-frequency noise. This paper is focused on the problem of inelastic resonant tunneling. We have calculated the average transparency for various relations between the switching rate of the dynamic defect, the escape rate of the electron from the resonant level in the well, the coupling strength between the electron and the dynamic defect, and the temperature. The results derived here are entirely different from those found in phonon-assisted resonant tunneling, because phonons obey the Bose statistics but a two-level fluctuator behaves as an effective spin.

Several aspects of the electronic properties of a three-tile model of one-dimensional quasiperiodic lattices have been studied. A canonical procedure to obtain the trace map is presented. The numerical simulation shows that the electronic energy spectra are also Cantor-like, but have different self-similarity from that of the Fibonacci lattice. We have provided a P, Q matrix approach to study the zero-energy eigenstates, and a pseudo-seven-cycle of the matrix map has been found. An exact real-space renormalization-group decimation approach has been used to calculate the local density of states. The numerically obtained spectra are in good agreement with previous analytical results

We study the phonon modes and melting properties of two-dimensional Penrose lattices with fivefold rotational symmetry. We use a similarity transformation to reduce the numerical calculations, which also helps us determine analytically the degeneracies of the phonon modes. It is found that two-thirds of the modes are doubly degenerate and the remaining one-third nondegenerate. Using the mean-square atomic-displacement criterion of Lindemann, we have studied the melting properties of two-dimensional Penrose lattices and found that the boundary atoms always have a lower melting temperature than those in the bulk.

With the help of the renormalization method we have calculated the low-temperature expansion series of free energy for the Ising models that are based on a fractal structure and with zero critical temperature. The results show that there exists a critical value of vd\ifmmode\bar\else\textasciimacron\fi{} such that, when vd\ifmmode\bar\else\textasciimacron\fi{} is larger than the critical value, scaling theory fails and the hyperscaling law is broken. We also found that the Ising models with zero critical temperature belong to two series of universality classes, respectively, one of which mainly corresponds to the Ising models based on the lattices generated in a site self-similar manner, which are named site-hierarchical lattices. Another series involves all Ising models that are based on other fractal structures. These two universality classes have different critical conditions of scaling and approach different thermal exponents \ensuremath{\alpha} when vd\ifmmode\bar\else\textasciimacron\fi{} becomes larger than the critical value.

Although there may exist a large intrasite Coulomb repulsion, the local mode can still induce a attractive interaction between electrons through oxygen breathing mode. This interaction plays an imporatnt role in raising Tc. The result approaches that of experiment by a combination of the local mode and the Van Hove singularity.

We proposed that BCS-like Hamiltonian with quasi-two-dimensional tight-binding electrons describe the Ba-La-Cu-O system approximately. Tc was calculated under the cases both negligible and non-negligible weak coupling between neighbor layers. It is found that the results we obtained approach that of experiments.

From nearly half-filled Hubbard model, under second order degenerate perturbation, we obtained an approximate effective Hamiltonian defined in non-doubly occupied space, Which is the same as that proposed by P.W. Anderson et al(1, 2). A little different considerations from that in Ref.2 have been made, which causes the relation between chemical potential u and doping parameter δ is different. Tc/t was calculated at different t/U. The results we obtained are also different from that in Ref.2 at some extent, especially for δ→0. It is found that Tc is in the region of experiment results under reasonable parameter t and U.