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Localization length in anderson insulator with Kondo impurities
1I. Institut für Theoretische Physik, Universität Hamburg, Hamburg 20355, Germany.
Physical Review Letters
|May 7, 2003
Summary
The localization length in 2D Anderson insulators is affected by magnetic impurities and Kondo correlations. A critical impurity concentration prevents unitary localization, leading to reentrant behavior and giant magnetoresistance.
Area of Science:
- Condensed matter physics
- Quantum mechanics
- Materials science
Background:
- Anderson insulators exhibit electron localization due to disorder.
- Electron spin scattering by magnetic impurities influences localization length.
- Kondo correlations introduce a feedback mechanism between scattering time and localization length.
Purpose of the Study:
- To investigate the impact of magnetic impurities and Kondo correlations on electron localization in 2D Anderson insulators.
- To determine the conditions for unitary localization and explore its dependence on impurity concentration and conductance.
- To analyze the effect of a parallel magnetic field on Kondo correlations and magnetoresistance.
Main Methods:
- Theoretical analysis of electron localization in disordered systems.
- Modeling of spin scattering by magnetic impurities with antiferromagnetic exchange.
- Investigation of Kondo correlations and their dependence on localization length.
- Calculation of the dependence of localization length on dimensionless conductance.
- Analysis of the influence of a parallel magnetic field.
Main Results:
- Unitary localization is impossible below a critical magnetic impurity concentration (n(c)).
- For concentrations above n(c), the localization length exhibits reentrant behavior with increasing conductance, transitioning between unitary and orthogonal regimes.
- Kondo correlations are sensitive to weak parallel magnetic fields, leading to giant parallel magnetoresistance.
Conclusions:
- The interplay between magnetic impurities, Kondo correlations, and disorder dictates electron localization properties in 2D systems.
- A critical threshold of magnetic impurity concentration is necessary for observing specific localization behaviors.
- Giant magnetoresistance effects can arise from the field sensitivity of Kondo correlations in these systems.
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