Excitons in carbon nanotubes with broken time-reversal symmetry.

Phys Rev Lett

Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA.

Published: January 2006

Near-infrared magneto-optical spectroscopy of single-walled carbon nanotubes reveals two absorption peaks with an equal strength at high magnetic fields (>55 T). We show that the peak separation is determined by the Aharonov-Bohm phase due to the tube-threading magnetic flux, which breaks the time-reversal symmetry and lifts the valley degeneracy. This field-induced symmetry breaking thus overcomes the Coulomb-induced intervalley mixing which is predicted to make the lowest exciton state optically inactive (or dark).

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http://dx.doi.org/10.1103/PhysRevLett.96.016406DOI Listing

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