Nature 410, 189–192 (2001).

This manuscript was, in part, the subject of an independent investigation1 conducted at the behest of Bell Laboratories, Lucent Technologies. The independent committee reviewed concerns related to the validity of data associated with the device measurements described in the paper. As a result of the committee's findings, we are issuing a retraction of the paper. We note nevertheless that this paper may also contain some legitimate ideas and contributions.