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Resonant Tunnelling Studies of Chaos in Quantised Systems

100%

Eaves L., Fromhold T., Wilkinson P., Sheard F.

Acta Physica Polonica A

1997

vol. 92

issue 4

609-619

This paper gives a brief introductory overview of quantum chaology, with particular reference to recent experimental work involving the use of semiconductor heterostructures. In the presence of a tilted magnetic field, a double-barrier resonant-tunnelling device incorporating a quantum well produces a chaotic stadium for electron motion. The basic properties of this system are described. It is shown how resonant magnetotunnelling spectroscopy provides firm experimental evidence for the effect of scarred wave functions on a physically-measurable property, in this case the measured current-voltage characteristics of the device. The paper concludes with some speculations concerning for the development of this field.

Stochastic Carrier Dynamics in Semiconductor Superlattices

52%

Fromhold T., Bujkiewicz S., Patanè A., Stapleton S., Sherwood D., Fowler D., Cooper J., Eaves L., Belyaev A., Krokhin A., Neumann A., Wilkinson P., Sankeshwar N., Henini M., Sheard F.

Acta Physica Polonica A

2006

vol. 109

issue 1

43-52

We explore a new regime of hot carrier dynamics, in which electrons in a superlattice miniband exhibit a unique type of stochastic motion when a magnetic field is tilted at an angleθ to the superlattice axis. Remarkably, the dynamics of a miniband electron in a tilted magnetic field reduce to a one-dimensional simple harmonic oscillator, of angular frequencyω_C cosθ, whereω_C is the cyclotron frequency, driven by a time-dependent plane wave whose angular frequency equals the Bloch frequencyω_B. At bias voltages for whichω_B=nω_C cosθ, where n is an integer, the electron orbits change from localised Bloch-like trajectories to unbounded stochastic orbits, which diffuse rapidly through intricate web patterns in phase space. To quantify how these webs affect electron transport, we make drift-diffusion calculations of the current-voltage curves including the effects of space-charge build up. When the magnetic field is tilted, our simulations reveal a large resonant peak, which originates from stochastic delocalisation of the electron orbits. We show that the corresponding quantised eigenstates change discontinuously from a highly localised character when the system is off resonance to a fully delocalised form when the resonance condition is satisfied.

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2 Acta Physica Polonica A

1 2006

1 1997

2 Eaves L.

2 Fromhold T.

2 Sheard F.

2 Wilkinson P.

1 Belyaev A.

1 Bujkiewicz S.

1 Cooper J.

1 Fowler D.

1 Henini M.

1 Krokhin A.

1 Neumann A.

1 Patanè A.

1 Sankeshwar N.

1 Sherwood D.

1 Stapleton S.

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Resonant Tunnelling Studies of Chaos in Quantised Systems

Stochastic Carrier Dynamics in Semiconductor Superlattices