Tuning into Hidden Levels

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Science  11 Feb 2000:
Vol. 287, Issue 5455, pp. 933
DOI: 10.1126/science.287.5455.933f

Electrons confined to move in a plane form a two-dimensional electron system, or 2DES. Application of a magnetic field perpendicular to this plane causes the electrons to redistribute into degenerate quantized magnetic sublevels, or Landau levels (LLs), where they occupy a ladder of discrete energy levels. Those discrete levels below the Fermi level (EF) are fully occupied, while those above the EF are empty. It is the properties of these LLs—their width, separation and energy—that determine the electronic behavior of two-dimensional conductors. Most experiments, however, probe only those LLs that are made to pass through EF and reveal little about the structure or dynamics of the levels below EF. Main et al. show how to extract the properties of these hidden levels directly. They placed a quantum dot next to the 2DES and then tuned the energy level of the quantum dot so that resonant tunneling occurred with a “buried” LL.—ISO

Phys. Rev. Lett.84, 729 (2000).

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