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All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

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Integer quantum Hall effect on a six-valley hydrogen-passivated silicon (111) surface.

K Eng¹, R N McFarland, B E Kane

¹Laboratory for Physical Sciences, University of Maryland at College Park, College Park, Maryland 20740, USA.

Physical Review Letters

|August 7, 2007

Summary

Magnetotransport studies reveal broken valley degeneracy in a two-dimensional electron system on hydrogen-passivated Si(111). This leads to unequal valley occupation and resistance anisotropy, challenging noninteracting electron theories.

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Area of Science:

Condensed matter physics
Surface science
Materials science

Background:

Two-dimensional electron systems (2DES) are crucial for understanding quantum phenomena.
The Si(111) surface offers a unique platform for creating 2DES at the interface with vacuum.
Valley degeneracy in such systems is typically expected to be sixfold.

Purpose of the Study:

Investigate magnetotransport properties of a 2DES at a hydrogen-passivated Si(111)-vacuum interface.
Determine the valley occupation and its effect on electronic properties.
Explore the implications for theoretical models of quantum Hall effects.

Main Methods:

Magnetotransport measurements were performed.
Studies were conducted in the integer quantum Hall regime.
The two-dimensional electron system was formed in an inversion layer.

Main Results:

The expected sixfold valley degeneracy was found to be broken.
Unequal occupation of the six valleys was observed.
Anisotropy in electrical resistance was detected, correlating with valley occupation.

Conclusions:

Surface misorientation likely breaks valley states into unequally spaced pairs.
Observed odd filling factors present a challenge to noninteracting electron theories.
Further theoretical and experimental investigation is needed to fully explain the findings.