Nature 403, 408–410 (2000).

Several papers were recently 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 those papers. As a result of the committee's findings, we have issued retractions of those papers. Furthermore, because of the extensive and serious nature of the committee's findings relating to the manuscripts that they examined, we are additionally concerned about aspects of the data presented in this paper. As we cannot vouch for the validity of the data, we wish to withdraw our support for the paper and issue a retraction.

The first author of this paper (J.H.S.), who was responsible for most of the experimental work, wishes to be dissociated from this retraction because he believes in the science presented in this manuscript.