Wu Hang-Sheng

High-Tc superconductor

Abstract In this Communication, we point out that it is possible to realize a high- T c superconductor with the electron-phonon interaction. A model for it is proposed and the possibility whether the recently discovered superconducting material with T c = 100K is the superconductor of this kind is discussed.

Peculiarity of high-Tc oxide superconductors

Abstract The following conclusions are arrived through analyzing the experiments: 1) The peculiarity of the high-Tc oxide superconductors BaPbBiO, LaSrCuO and YBaCuO is that their pseudo-Coulomb potentials μ∗ are negative quantities. 2) The superconductivity of these three oxides can be understood within the framework of the conventional BCS-Eliashberg theory if the said peculiarity is taken into account in the theory.

A possible effect caused by spin fluctuations in CuO2 planes in HTSC

In the present letter, we study the magnetic contribution to the thermal expansion of Cu−O layer in YBa2Cu3O7−δ with the nearly antiferromagnetic Fermi liquid model. Our analysis suggest that this additional thermal expansion due to antiferromagnetic spin fluctuation is the origin of the Cu−O plane buckling.

Influence of the Pseudogap on the Inelastic Neutron Scattering Spectra of the Underdoped Lanthanum Cuprate

The influence of pseudogap on the inelastic neutron scattering spectra of the underdoped lanthanum cuprate is studied on the basis of the model which incorporates both the superconducting state and pseudogap state. It is found that the striking effects of the influence of the pseudogap on the incommensurability of the spin excitation spectrum are that in the superconducting state the pseudogap makes the intensity of the incommensurate peak increase, in the normal state the pseudogap not only makes the intensity of the incommensurate peak increase, but also sharpens the incommensurate peak and increases incommensurability.

Classical Theory of Hot-Electron Transport in Electric and Magnetic Fields

Balance equation approach to the hot-electron transport in electric and magnetic fields is reformulated. The balance equations are re-derived from the Boltzmann equation. A new expression for the distribution function is reported in the present paper. It is homogeneous steady solution of the Boltzmann equation in constant relaxation time approximation. It holds when or . As an example, the mobility of 2D electron gas in the GaAs-AlGaAs heterojunction is computed as a function of electric field and magnetic field.

The c-Axis Infrared Conductivity of a dx2-y2-Wave Superconductor with the Hopping Assisted by the Spin Fluctuations*

A theory of the c-axis infrared conductivity of a dx2-y2-wave superconductor due to the competition between the interlayer direct hopping and the hopping assisted by the spin fluctuations has been developed. The prediction of our theory captures the main feature of the experiment. Thus we argue that the anomalous behavior of the c-axis infrared conductivity of the underdoped cuprates in superconducting state may be properly understood within the theory.

Study of Pseudogap in Underdoped Cuprate

A mean-field spin-density wave (SDW) analysis of pseudogap in the underdoped cuprates is proposed on the basis of the Hubbard model. It is surprised to find that a simple term will do the trick to introduce the momentum dependence of the energy gap which mimics the pseudogap near point at least. It implies that the pseudogap structure near is not sensitive to the long-range order and will survive leading to the pseudogap phenomenon in the underdoped metallic phase. On the other hand, in the long-range ordering antiferromagnetic region, the mean-field SDW theory holds and the pseudogap structure predicated by the theory should be observable experimentally. Then one prediction is that the pseudogap would smoothly extrapolate between itinerant antiferromagnetic phase and underdoped metallic phase.

Two-dimensional hot-electron transport in GaAs-AlGaAs heterojunctions

The mobility of a two-dimensional electron gas in GaAs-AlGaAs heterojunction is recomputed through solving numerically the balance equation. The peculiarity of the present study lies in that a new expression for the distribution function and the renormalized phonon frequency are used in the computation. Compared with those reported by previous authors, our result shows better agreement with the experimental data.

A Possible Origin of Cu-O Plane Buckling in YBa2Cu3O7

The magnetic contribution to the thermal expansion of Cu-O layer in YBa2Cu3O7-δ is studied with the nearly antiferromagnetic Fermi liquid model. Our analysis suggests that this additional thermal expansion due to antiferromagnetic spin fluctuation is the origin of the Cu-O plane buckling.

RVB-Itinerant P Hole Model for High-Tc Copper Oxides

A model for the high-Tc Copper Oxides is studied. The localized nature of Cu 3d electrons is described as the RVB quantum spin liquid and the doped O 2p holes are described with an itinerant band. Our analysis shows that the virtual exchange of two spinons induces a pairing interaction between two holes.