Locality and topology in the molecular Aharonov-Bohm effect

It is shown that the molecular Aharonov-Bohm effect is neither nonlocal nor topological in the sense of the standard magnetic Aharonov-Bohm effect. It is further argued that there is a close relationship between the molecular Aharonov-Bohm effect and the Aharonov-Casher effect for an electrically neutral spin$-{1/2}$ particle encircling a line of charge.Comment: 3 pages, no figure

The Born-Oppenheimer Approach to the Matter-Gravity System and Unitarity

The Born-Oppenheimer approach to the matter-gravity system is illustrated and the unitary evolution for matter, in the absence of phenomena such as tunnelling or other instabilities, verified. The Born-Oppenheimer approach to the matter-gravity system is illustrated in a simple minisuperspace model and the corrections to quantum field theory on a semiclassical background exhibited. Within such a context the unitary evolution for matter, in the absence of phenomena such as tunnelling or other instabilities, is verified and compared with the results of other approaches. Lastly the simplifications associated with the use of adiabatic invariants to obtain the solution of the explicitly time dependent evolution equation for matter are evidenced.Comment: Latex, 12 pages. Revised version as accepted for publication by Class. and Quant. Grav. Some points explained and misprints correcte

Experimental Determination of E−k Relationship in Electron Tunneling

We report here measurements of electron tunneling through thin AlN films in which the imaginary component of the propagation vector in the forbidden band has been determined as a function of energy from the dependence of the tunneling current upon insulator thickness. The relationship so derived agrees well with Franz's empirical relationship for a material with the 4.2-eV forbidden-band energy of AlN. These results allow the prediction of voltage-current characteristics over the entire range of experimental variables with no arbitrary adjustable parameters, and also subject to several internal self-consistency checks. In each case complete consistency is observed, To the authors' knowledge, this represents the first unambiguous demonstration of such consistency in thin-film tunneling

Energy-Momentum Relationship in InAs

We have performed surface-barrier tunneling measurements on p-type InAs and found the energy dependence of the wave vector in the forbidden gap to be in agreement with Franz's relationship based on a two-band model

Tunneling in CdTe Schottky Barriers

The tunneling characteristics of metal contacts on n−CdTe have been measured. Both the forward- and reverse-bias characteristics are in good agreement with the two-band model for the energy-complex-momentum relationship. The presence of trapping states increased the magnitude of the tunneling current at low levels by providing a two-step transition. The slope of the forward-bias log_e J−versus−V curves for tunneling through the intermediate states was reduced by a factor of 2

Fermi Level Position at Semiconductor Surfaces

There have been several recent reports of barrier height studies on metal-semiconductor interfaces. Metals of widely different work functions evaporated onto Si and GaAs surfaces indicated that in each case the energy difference between the semiconductor conduction band edge and Fermi level at the interface,φ_(Bn), was essentially independent of the metal, which indicates that the Fermi level is fixed by surface states. In the present work barrier height measurements have been made on a number of zinc-blende semiconductors to determine (a) if the barriers are in all cases determined by surface states, and (b) the relation between the Fermi energy at the interface and the band gap E_g

Conduction Band Minima in AlAs and AlSb

The photoresponse of surface barrier rectifiers made by evaporating a metal such as gold or platinum on a cleaved surface of AlAs and AlSb has been measured in the front wall configuration. The photoresponse of such units for hv > E_g, where E_g is the energy gap, will be proportional to the absorption coefficient as long as the optical attenuation length is large compared to both the width of the space-charge region and the minority carrier diffusion length. The analysis is essentially the same as that for p-n junctions with the exception that the barrier is at the surface and hence more sensitive to photons of high absorption coefficient. Photoinjection of carriers from the metal into the semiconductor for photon energies where hv < E_g can also be observed

Voltage Dependence of Barrier Height in AIN Tunnel Junctions

We report measurements of barrier heights on AI-AIN-Mg thin-film structures as a function of applied voltage and insulator thickness. These results are in disagreement with currently accepted theories based upon image potential and/or field penetration of the electrodes

The Effect of Trapping States on Tunneling in Metal Semiconductor Junctions

The tunneling behavior of Schottky barriers has been investigated by several authors. The I-V characteristics exhibit an exponential form in the forward direction which can be used to determine the energy vs complex momentum dispersion relation for charge carriers in the forbidden gap. In this paper we show that under proper conditions the presence of traps can increase the tunneling probability and result in a reduction in the slope of the log I vs V characteristic by a factor of 2