▎ 摘　　要

With the help of electron spin-coherent-state, we theoretically investigate the quantum tunneling time of a Dirac electron through a rectangular potential-barrier in monolayer graphene. It is shown that the tunneling time, which is measured in terms of the electron-spin precession in the magnetic field confined in the barrier region, is equal to the dwell time. Moreover, when the wave function in barrier is an oscillating mode, the curve of tunneling-time against the barrier-width oscillates around an increasing average-line. While for the wave function of an evanescent mode, the tunneling time is independent of the barrier width. In particular, the tunneling time just equals the potential width divided by the Fermi velocity in the Klein tunneling. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4789636]