Biomedical subjects

Alexander Punnoose

Publications and source records attributed to Alexander Punnoose.

3 recordsLinked to original sources

PubMed2006

Spin relaxation in the presence of electron-electron interactions.

The D'yakonov-Perel' spin relaxation induced by the spin-orbit interaction is examined in disordered two-dimensional electron gas. It is shown that, because of the electron-electron interactions, substantially different spin relaxation rates may be observed depending on the technique used to extract them. It is demonstrated that the relaxation rate of a spin population is proportional to the spin-diffusion constant D(s), while the spin-orbit scattering rate controlling the weak-localization corrections is proportional to the diffusion constant D, i.e., the conductivity. The two diffusion constants get strongly renormalized by the electron-electron interactions, but in different ways. As a result, the corresponding relaxation rates are different, with the difference between the two being especially strong near a magnetic instability or near the metal-insulator transition.

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PubMed2005

Metal-insulator transition in disordered two-dimensional electron systems.

We present a theory of the metal-insulator transition in a disordered two-dimensional electron gas. A quantum critical point, separating the metallic phase, which is stabilized by electronic interactions, from the insulating phase, where disorder prevails over the electronic interactions, has been identified. The existence of the quantum critical point leads to a divergence in the density of states of the underlying collective modes at the transition, causing the thermodynamic properties to behave critically as the transition is approached. We show that the interplay of electron-electron interactions and disorder can explain the observed transport properties and the anomalous enhancement of the spin susceptibility near the metal-insulator transition.

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PubMed2001

Dilute electron gas near the metal-insulator transition: role of valleys in silicon inversion layers.

We emphasize the role of valleys in the transport properties of the dilute electron gas in Si-MOSFETs. Close to the critical region of the metal-insulator transition the decrease in the resistivity up to 5 times has been captured in the correct temperature interval by a renormalization group analysis of the interplay of interaction and disorder. No adjustable parameters are involved in the analysis if the electron band is assumed to have two distinct valleys. The considerable variance in the data obtained from Si-MOSFET samples of different quality is attributed to the sample-dependent scattering rate across the two valleys, while universal behavior is expected to hold when the intervalley scattering is negligible.

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