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Laser-Based Exitonic Circuits

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11:00 – 12:00 29 Feb 2016
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Room C1060
Dept of Physics and Energy
University of Limerick
Limerick

Speakers: Prof Mark Lusk, Colarado School of Mines

A combined theoretical and computational analysis is used to show that a laser can create coherent superpositions of excitons that move with a speed, profile and footprint engineered via pulse shaping. The resulting excitonic wave packet amounts to a quasiparticle with a speed that can be prescribed by adjusting the shape of the laser pulse. Superlattices composed of alternating layers of material can be used to induce band pass or band top filters that discriminate between excitonic quasiparticles with differing central wavenumber. Packet energy and information can be subsequently removed at a distant site by reversing the original procedure using a laser pulse to produce a stimulated emission. These properties constitute the building blocks for excitonic circuits with optical coupling at either end. The idea is subsequently extended to consider lattices with a tunable control site that can be used to create local quantum interference. This results in a form of Fano anti-resonance that blocks the transmission of the quasiparticles within an adjustable small band of wavenumbers. A potential bias can therefore be used to gate the motion of energy and information. When implemented within nanoscale assemblies, such control elements provide an additional means of creating excitonic circuits. Alternatively, transmission of electons but blocking of holes could be used to dissociate excitons. Two extremes of anti-resonant behaviour are identified: one in which the exciton moves as a single particle, and the other in which partial dissociation is an integral part of the quantum interference. Idealised implementations with Hubbard-like Hamiltonians are used to examine the basic physics of excitonic crystals, but time-dependent density functional theory implementations will be discussed as well. Mark Lusk studied solid state physics at the U.S. Naval Academy and was subsequently a naval nuclear engineer. He obtainedhis PhD in Applied Mathematics at the California Institute of Technology. Mark's research focuses on theoretical and computational queries, related to the exceited states of nano structured assemblies with an emphasis on quantum transport and optical interactions with matter. He is the lead theorist with with the NSF sponsored Renewable Energy Materials Research Science and Engineering Research Centre and the lead scientist for high performance computing research at the Colorado School of Mines.

Event type: Lecture/Talk
Sponsored by: IOP Ireland
Organised by: iop Ireland/UL
Contact details: Carol Ryan, e: carol.ryan@ul.ie t: 061 21 3113

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Location icon
Room C1060
Dept of Physics and Energy
University of Limerick
Limerick
Clock icon
11:00 – 12:00 29 Feb 2016
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