Computational quantum transport in mesoscopic electronic waveguides
Zusammenfassung der Projektergebnisse
In the present project on quantum transport in two-dimensional mesoscopic structures, major progress has been achieved in understanding the interplay of general geometrical characteristics with the effects of magnetic fields on electronic propagation, and intriguing possibilities of current flow control have been demonstrated. We have performed extensive magnetotransport investigations of systems of two- or multiple-terminal quantum dots, as single scatterers or assembled into linear and lateral arrays. For the demanding transport calculations of connected-dot systems, a highly efficient computational approach was developed, based on the partition of the complete structure into modules which are subsequently inter- or intra-connected, while retaining the flexibility of multiterminal configuration and device design. In addition, a parallelization scheme was developed to lower the computational cost on the single-dot level. Our results show a remarkable controllability of transmission already through two-terminal single dots, based on their property to geometrically separate confined eigenstates from leaking states coupling strongly to the attached leads. The ability to enhance or suppress the electronic current by tuning the magnetic field at low field strengths, was explained through the phase-sensitive interfering process of quasi-degenerate such separate leaking states, making the mechanism unique for the elongated type of the studied scatterers. In a multiterminal configuration, the guiding and focusing property of curved boundary sections enabled us to design a device which transmits ingoing current flow exclusively to any other output terminal at low temperatures. Relying on the combination of geometry and symmetry considerations with magnetic deflection and edge state propagation, this presents a major advance in designing mesoscopic transport elements based on fundamental principles. The combination of dots into linear arrays was shown to further enhance the magnetotransport controllability which, in all considered cases, proved to remain robust under weak disorder of the device bulk or boundary. General features of coupled-dot arrays, such as the formation and detection of quasi one-dimensional Bloch electrons, the accompanied magnetic transmission bands, as well as the distinction between Fano resonances and coupled-resonator spectral peaks, were thoroughly analyzed and explained. The efficient assembly of scattering units into multiply connected lateral arrays has opened the perspective of studying generalized Aharonov–Bohm oscillations in coupled loops, in correlation with resonant transport through connected dots.
Projektbezogene Publikationen (Auswahl)
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Magnetically controlled current flow in coupled-dot arrays. J. Phys.: Condens. Matter 19, 326209 (2007)
P. Drouvelis, G. Fagas, and P. Schmelcher
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Tunable transmission via quantum state evolution in oval quantum dots. Europhys. Lett. 81, 37001 (2008)
D. Buchholz, P. Drouvelis, and P. Schmelcher
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Magnetoconductance switching in an array of oval quantum dots. Phys. Rev. B 80, 035301 (2009)
C. Morfonios, D. Buchholz, and P. Schmelcher
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Magnetic field-induced control of transport in multiterminal focusing quantum billiards. Phys. Rev. B 83, 205316 (2011)
C. Morfonios, D. Buchholz, and P. Schmelcher
