Investigation of semiconductor based particle interferometers as quantum switches

Afif Sıddıki

İstanbul Universitesi Fizik Bölümü

Abstract/Özet: At low temperatures, low-dimensional electron systems show numerous peculiar quantum transport properties. One of the most interesting of such transport systems are the particle interferometers.Interferometers like Mach-Zehnder and Aharanov-Bohm are induced in a two-dimensional electron system (2DES) by metallic gate electrodes or chemical etching. The strong magnetic field applied perpendicular to the plane of the interferometers, quantize the current carrying statesand generates edge states where the current is carried without back-scattering, i.e. ballistic transport. These quantized edge states replace the (monochromatic) light beams at the optical versions of the optical interferometer(s), therefore a coherent transport takes place. Various unexpected findings of recent experiments performed at these (quantum Hall based) interferometers, indicate that an accurate treatment of interaction effects, taking full and realistic account of sample and geometry dependent details, is essential for a satisfactory understanding of the observed phenomena, such as the path length independent interference pattern. In this talk I will report on the findings of a promising theoretical candidate, namely the screening/interaction theory of the integer Hall effect. This approach was able to explain microscopically, both the vanishing Longitudinal resistance and the exact quantization of the plateaus, together with the transition between the plateaus. The measurements under quantized Hall conditions (B>2 Tesla and T<4 Kelvin) are not only performed considering integer charged particles, however, are also performed using fractionally charged (quasi-) particles which present interference patterns as well, and the patterns cannot be explained within non-interacting single particle theories. Here, I will address these issues using the self-consistent solution schemes of the Schrödinger-Poisson equations concerning the particle interferometers in various complex geometries (such as Mach-Zehnder and Aharonov-Bohm), within Hartree and spin dependent generalizations thereof, utilizing density functional theories. In doing so, we build on our previous work with this method, which was shown to describe successfully various subtle geometry-dependent effects observed in quantum Hall systems, and investigate different working regimes of the interferometers such as high/low temperature and magnetic field.

Yer : MSGSÜ Bomonti Binası, Fizik Bölümü.
Tarih : 22 Kasım 2012 Perşembe, 15:00
Ayrıntılı bilgi : msgsufizik.net