Experimental tests for boson condensation and superconductivity in semiconductors during pulsed beam annealing

Van Vechten and Compaan and, independently, Nagy and Noga have proposed that the high reflectivity state observed in pulsed laser/electron/ion beam annealing of Si and other semiconductors results when the electron-hole plasma created by the initial absorption of the ionizing radiation undergoes a boson condensation. The condensed state is described in the same form as the BCS superconductor and has many of the properties of the superconducting state. Lattice temperatures for the material during this phase have beeb measured by Raman scattering to lie in the range from 500 to 1000 K. At this writing no magnetic experiment has been completed to test this proposition further. In addition to the practical problems associated with such a test, there are theoretical questions such as whether or not the bipolar plasma ought to be able to expel a magnetic field within the 100 ns or so that it persists in the proposed boson condensed phase. If not, it does not exhibit perfect diamagnetism and the Meissner effect. An experiment is proposed that is argued to be both easy to perform and to offer a conclusive demonstration of boson condensation. The proposed experiment involves observation of the single plasmon mode by diffraction or from the appearance of linear ripples left on the solid surface and the rotation of this pattern. Preliminary observations seem to confirm the condensation.     

More about the energy spectrum and the function c(k) in the boson formulation of superconductivity

An analytical expression for the energy spectrum ω(k) of the collective mode is derived in the asymptotic region. In such a region the boson characteristic function c(k) is also suitable for an analytic expression.Calculations show that the function c(k) is exponentially damped: the electrodynamics of a superconductor is much more nonlocal than previously thought.     

Vector boson decays of the Higgs boson

We derive the width of the Higgs boson into vector bosons. General formulas are derived both for the on–shell decay as well for the off–shell decays, and , where . For the off-shell decays the width of the decaying vector boson is properly included. The formulas are valid both for the Standard Model as well as for arbitrary extensions. As an example we study in detail the gauge-invariant effective Lagrangian models where we can have sizable enhancements over the Standard Model that could be observed at LEP. Received: 31 July 1998 / Revised version: 23 September 1998 / Published online: 6 November 1998     

Surface superconductivity and twinning-plane superconductivity in aluminum

The critical supercooling field H _sc is measured in aluminum single crystals and twinned bicrystals in a temperature range slightly below T _c0 (T _c0 ? 0.055 K < T < T _c0), where T _c0 is the critical superconducting transition temperature. It is found that, even in this small temperature range, the H _sc(H _c) dependence, which is considered to be identical to the H _c3(H _c) dependence for single crystals, is substantially nonlinear. The H _sc(H _c) dependences of the twinned bicrystals and single crystals are shown to be significantly different. The qualitative features of the phase diagram of the twinned aluminum bicrystals coincide with those of the phase diagram of twinning-plane superconductivity obtained earlier for tin in [1]. These findings allow the conclusion that the phenomenon of twinning-plane superconductivity also exists in face-centered cubic crystal lattices.     

Derivation and application of quantum Hamilton equations of motion

Non‐relativistic quantum systems are analyzed theoretically or by numerical approaches using the Schrödinger equation. Compared to the options available to treat classical mechanical systems this is limited, both in methods and in scope. However, based on Nelson's stochastic mechanics, the mathematical structure of quantum mechanics has in some aspects been developed into a form analogous to classical analytical mechanics. We show here that finding the Nash equilibrium for a stochastic optimal control problem, which is the quantum equivalent to Hamilton's principle of least action, allows to derive two things: i) the Schrödinger equation as the Hamilton‐Jacobi‐Bellman equation of this optimal control problem and ii) a set of quantum dynamical equations which are the generalization of Hamilton's equations of motion to the quantum world. We derive their general form for the non‐stationary and the stationary case. For the harmonic oscillator, the stationary equations lead to the coherent states, and we establish a numerical procedure to solve for the ground state properties without using the Schrödinger equation.

     

Higgs boson production and weak boson structure

The influence of the QCD structure of the weak bosons on the Higgs boson production ine-p scattering is studied. The energy and Higgs boson mass dependence of the cross-section, following from the new contributions, is calculated. Work supported by the Polish State Committee for Scientifić Research (grant No. 2 P03B 081 09) and the Volkswagen-Stiftung     

Derivation of collective potential and mass from the generator coordinate method

The Hill-Wheeler equation of the generator coordinate method is approximated by a local collective Schrödinger equation. General expressions for the potential and the mass parameter are obtained by a symmetrized moment expansion. The validity of the approximation is tested for several examples where the exact solution is known. These include the Gaussian overlap with harmonic and anharmonic interaction, the Lipkin model, and monopole resonances of spherical light nuclei. In all cases, surprisingly close agreement with the exact solution is found. Other possible applications of the formalism are indicated.     

分子动力学方法中速度标度因子的推导

在使用分子动力学方法对微正则系综进行模拟的情况下,以单原子粒子系统为例,给出了标度因子在国际单位制下的数学表达式.然后说明了如何把物理量重新标度得到无量纲公式,使得在模拟中计算更加方便.给出了无量纲化操作中时间单位的物理意义.最后,推导了趋衡过程的速度标度因子在教材中常用的数学表达式.     

On the connection between the generator coordinate method and boson expansions for odd-particle systems

The generator coordinate method is used to derive a boson expansion for odd-particle systems which is equivalent to the Yamamura and Marshalek expansions.     

Derivation,properties and application of Coulomb Sturmians defined in spheroidal coordinates

Coulomb Sturmian amplitude functions are derived in prolate spheroidal coordinates and are presented in a closed algebraic form. Spheroidal Sturnian functions are revealed to be related to the polynomial solutions of Heun's confluent equation. A reduction of symmetry from spherical to axial leads to the coupling of spherical polar orbitals and the formation of hybrid orbitals. The contribution of each spherical orbital into a hybrid orbital depends strongly on distance R from a nucleus to the dummy centre, and substantially alters when R varies. At two limiting cases R = 0 and R → ∞ spheroidal Sturmians are purely atomic orbitals, whereas at intermediate R they contain many features intrinsic to diatomic molecular orbitals. Applications of spheroidal Sturmian basis are discussed; Coulomb spheroidal Sturmians are asserted to be the most appropriate basis functions for diatomic molecular calculations.     

Application of the Dyson boson expansion method to the treatment of the pairing force

The treatment of the separable pairing interaction in the context of the BRST formalism and in the Dyson boson expansion method is discussed. The approach is based on the use of the vacuum expectation value of the boson number operator to define a suitable mean field. Received: 10 April 2000 / Accepted: 6 July 2001     

Derivation of collective potentials and mass parameters from the generator coordinate method

By expanding the overlap and the hamiltonian kervels in the Hill-Wheeler equation into a series of hermitian differential operators, expressions for the collective potential and mass parameter are derived.     

Superfluidity and superconductivity in the universe

The paper aims to elucidate the current status of the problem concerning the existence and observation of superfluid and superconducting states in the universe, that is, under cosmic conditions. Following an introduction, the paper discusses Bose-Einstein condensation, superfluidity, and superconductivity; possibilities for the occurrence of superfluidity and superconductivity under cosmic conditions; superconductivity of dense, degenerate electron plasma (large planets, white dwarfs); superfluidity and superconductivity in neutron stars; and finally superfluidity in a cosmological neutrino “sea.”     

Topological change of the Fermi surface in low-density Rashba gases: application to superconductivity

In this Letter we show how, for small values of the Fermi energy compared to the spin-orbit splitting of Rashba type, a topological change of the Fermi surface leads to an effective reduction of the dimensionality in the electronic density of states in the low charge density regime. We investigate its consequences on the onset of the superconducting instability. We show that the superconducting critical temperature is significantly tuned in this regime by the spin-orbit coupling. We suggest that materials with strong spin-orbit coupling are good candidates for enhanced superconductivity.     

Bosonic mode interpretation of novel scanning tunnelling microscopy and related experimental results,within boson–fermion modelling of cuprate high-temperature superconductivity

This paper seeks to synthesize much recent work on the cuprate high-temperature superconductors around the latest energy-resolved scanning tunnelling microscopy (STM) results from Davis and co-workers. The STM conductance diffuse scattering results in particular are employed as point of entry to discuss bosonic modes, of both condensed and uncondensed form. The bosonic mode picture is essential to understanding an ever-growing range of observations within the high-temperature superconductivity field (HTSC). The work is expounded within the context of the site-inhomogeneous negative-U boson–fermion modelling long advocated by the present author. This general approach is at present seeing much theoretical development, into which I have looked to couple many of the experimental advances. While this formal theory is not yet sufficiently detailed to cover adequately all the experimental complexities presented by the real cuprate systems, it is clear that it affords very appreciable support to the line taken. An attempt is made throughout to clarify why and how it is that these novel circumstances and phenomena are tied so very closely to this particular set of materials.     

正交曲线坐标系中加速度的矢量求法

利用矢量法,给出一种求解正交曲线坐标系中加速度的简捷方法。     

Derivation and application of the reciprocity relations for radiative transfer with internal illumination

A Green's function formulation is used to derive basic reciprocity relations for planar radiative transfer in a general medium with internal illumination. Reciprocity (or functional symmetry) allows an explicit and generalized development of the equivalence between source and probability functions. Assuming similar symmetry in three-dimensional space, a general relationship is derived between planar-source intensity and point-source total directional energy. These quantities are expressed in terms of standard (universal) functions associated with the planar medium, while all results are derived from the differential equation of radiative transfer.