Dubeibe Marín, Fredy Leonardo - Bombas de espín clásicas y cuánticas - Classical and quantum spin pumps - 183154.2010Reportar como inadecuado




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Dubeibe Marín, Fredy Leonardo - Bombas de espín clásicas y cuánticas - Classical and quantum spin pumps - 183154.2010 - 53 Física - Physics


Introducción



Classical and Quantum Spin Pumps Disertaci´on para optar al t´ıtulo de Doctor en Ciencias-F´ısica de la Universidad Nacional de Colombia por Fredy Leonardo Dubeibe Mar´ın Bogot´ a, Junio de 2010 Classical and Quantum Spin Pumps Fredy Leonardo Dubeibe Mar´ın C´odigo 183154 Disertaci´on para optar al t´ıtulo de Doctor en Ciencias-F´ısica de la Universidad Nacional de Colombia Dirigido por Prof.
Thomas Dittrich Universidad Nacional de Colombia Facultad de Ciencias Departamento de F´ısica Bogot´ a, Junio de 2010 Abstract Directed transport in classical and quantum pumps is studied in a specific model, a magnetic dipole moving in a periodically modulated magnetic field confined to a compact region in space.
For the classical case, we show that this system is an irregular scatterer in large parts of its parameter space.
If all spatio-temporal symmetries are broken, directed transport of mass as well as angular momentum occurs.
The sensitive parameter dependence of the corresponding currents includes frequent sign reversals.
Zeros of either current quantity correspond to the exclusive occurrence of the other and thus give rise in particular to angular-momentum separation without mass transport as a classical analogue of spin-polarized currents.
For the quantum case, we show that the basic mechanism responsible for the separation of spins in the classical case carries over to the quantum level, giving rise to a spin pump capable of generating polarized spin currents.
We illustrate and confirm our theory with numerical data obtained from wave packet scattering as well as from a numerical solution of the Schr¨odinger equation with source term, and show how the scattering parameters for individual Floquet channels are extracted from the raw data. ii “In life, time is the solution to almost all the problems. In physics, time is the problem to almost all the solutions.” Acknowledgments I would like to thank all people who have helped a...






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