Novel non-local behaviour of quasi-3D Wide Quantum Wells

We investigate the high magnetic field regime of wide quantum wells (WQW) for the case of a many valley host semiconductor. The complete system is described within a modified Landauer-Buettiker formalism and we demonstrate that a parallel contribution of two electron systems in different valleys of the band structure can lead to an edge channel related non-local behaviour even in the 3D-regime. From the obtained general result we derive also a simplified model which applies for the case of much different dissipation. It represents the most dissipative system by an Ohmic resistor network and the less dissipative system by an EC-system.Comment: postscript file including 3 figs, 4 page

Anomalous magnetotransport in wide quantum wells

We present magneto transport experiments of quasi 3D PbTe wide quantum wells. A plateau-like structure in the Hall resistance is observed, which corresponds to the Shubnikov de Haas oscillations in the same manner as known from the quantum Hall effect. The onsets of plateaux in Rxy do not correspond to 2D filling factors but coincide with the occupation of 3D (bulk-) Landau levels. At the same time a non-local signal is observed which corresponds to the structure in Rxx and Rxy and fulfils exactly the Onsager-Casimir relation (Rij,kl(B) = Rkl,ij(-B)). We explain the behaviour in terms of edge channel transport which is controlled by a permanent backscattering across a system of "percolative EC - loops" in the bulk region. Long range potential fluctuations with an amplitude of the order of the subband splitting are explained to play an essential role in this electron system.Comment: postscript file including 3 figs, 5 page

Can We Test for Bias in Scientific Peer-Review?

Science rests upon the reliability of peer review. This paper suggests a way to test for bias. It is able to avoid the fallacy -- one seen in the popular press and the research literature -- that to measure discrimination it is sufficient to study averages within two populations. The paper’s contribution is primarily methodological, but I apply it, as an illustration, to data from the field of economics. No scientific bias or favoritism is found (although the Journal of Political Economy discriminates against its own Chicago authors). The test’s methodology is applicable in most scholarly disciplines

Commentary on three papers

Let me start with “The Slump, the Recovery, and the New Normal” by Edmund Phelps. With this stone, I would like to hope that I am killing two birds: Ned Phelps’s paper is, in part, a non-mathematical version of the “Macroeconomic Effects of Over-Investment in Housing in an Aggregative Model of Economic Activity”, written by Hian Teck Hoon. The first paper is in words; the second has some words and, in parts, some Hamiltonians. Both papers are extraordinarily stimulating. Both bear on the issues of the day. A key thing to say, and admire, about the first paper is the fact that in a fairly readable way — not that it will be an effortless read for the non-economist — it addresses the great macroeconomic issue of our time. Why did the remarkable financial crisis of the first decade of the 2000s come about, and what happens next? Phelps begins by pointing out that we experienced a major contraction before in the post-war era, namely, during the severe downturn that began around the mid 1970s and took unemployment levels to a frightening point seen by few living worker (in my country, the UK, unemployment was 12% of the labour force by the year 1983). That crisis took place as I was in the middle of college; it encouraged in me an interest in economics

Happiness and economic performance

If a nation's economic performance improves, how much extra happiness does that buy its citizens? Most public debate assumes -- without real evidence -- that the answer is a lot. This paper examines the question by using information on well-being in Western countries. The data are of four kinds: on reported happiness, on reported life satisfaction, on reported job satisfaction, and on the number of suicides. These reveal patterns that are not visible to the anecdotal eye. In industrialized countries, well-being appears to rise as real national income grows. But the rise is so small as to be sometimes almost undetectable. Unemployment, however, seems to be a large source of unhappiness. This suggests that governments ought to be trying to reduce the amount of joblessness in the economy. In a country that is already rich, policy aimed instead at raising economic growth may be of comparatively little value

Magnetotransport in wide parabolic PbTe quantum wells

The 3D- and 2D- behaviour of wide parabolic PbTe single quantum wells, which consist of PbTe p-n-p-structures, are studied theoretically and experimentally. A simple model combines the 2D- subband levels and the 3D-Landau levels in order to calculate the density of states in a magnetic field perpendicular to the 2D plane. It is shown that at a channel width of about 300nm on can expect to observe 3D- and 2D-behaviour at the same time. Magnetotransport experiments in selectively contacted Hall bar samples are performed at temperatures down to T = 50 mK and at magnetic fields up to B = 17 T.Comment: postscript file including 2 figs, 4 pages, Paper presented at EP2DS-XI, Nottingham 199

Conductance Fluctuations in PbTe Wide Parabolic Quantum Wells

We report on conductance fluctuations which are observed in local and non-local magnetotransport experiments. Although the Hall bar samples are of macroscopic size, the amplitude of the fluctuations from the local measurements is close to e^2/h. It is shown that the fluctuations have to be attributed to edge channel effects.Comment: postscript file including 3 figs, 3 pages, Paper presented at 3rd Int. Symposium on "New Phenomena in Mesoscopic Structures" in Maui, Hawaii 199