  A recently published report in the journal Science claims that the Datta-Das
Spin Field Effect Transistor has been demonstrated because an exact agreement
was found between the voltage modulation in a fabricated structure and a
theoretical equation that supposedly describes the voltage modulation of the
Datta-Das Transistor. Here, I show that the said theoretical equation holds
only for a one-dimensional transistor, or perhaps a quasi one-dimensional
transistor, and is certainly not applicable to the two-dimensional transistor
studied. Hence, the exact agreement is meaningless and does not substantiate
the claim.

Mesoscale and Nanoscale Physics;Other Condensed Matter