PHYSICS: Quantum Interference in Minibands

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Science  09 Mar 2001:
Vol. 291, Issue 5510, pp. 1863c
DOI: 10.1126/science.291.5510.1863c

In a three-dimensional crystal, the periodicity of the lattice can give rise to the formation of electronic energy bands and band gaps. Artificial superlattices, such as those comprising an alternating stack of GaAs and AlGaAs layers, also are periodic and can form similar structures called minibands that are isolated by minigaps. In the presence of a magnetic field, electrons residing within the minibands of a spatially modulated two-dimensional electron system (2DES) may interact with each other. Quantum interference effects would be expected when electrons tunnel between minibands to form closed electron orbits, or when the electrons backscatter, which results in interference along open electron paths. However, a short spatial periodicity and a large electron density modulation in the 2DES have been difficult to achieve, which has made it hard to see such quantum-intereference effects.

Deutschmann et al. have succeeded in depositing a high-quality, spatially modulated 2DES along the edge of a stacked superlattice structure, where the controlled growth (with atomic layer resolution) of the superlattice provides the requisite spatial periodicity. The observed oscillations in the magnetotransport data are consistent with quantum-interference effects along closed orbits associated with the artificial lattice. — ISO

Acknowledgments

Phys. Rev. Lett. 86, 1857 (2001).

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