PerspectivePhysics

STM Ready for the Time Domain

Science  24 Sep 2010:
Vol. 329, Issue 5999, pp. 1609-1610
DOI: 10.1126/science.1194918

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Summary

The capabilities of the scanning tunneling microscope (STM) have moved well beyond locating atoms on surfaces. The STM has been used to image electronic wave functions (1) and magnetic structures (2). It has also emerged as a tool to measure the energy of the vibrations of adsorbed molecules (3) or surface phonons (4), as well as spin excitations of adsorbed species (5) or surface spin waves (magnons) (6), by using so-called inelastic spectroscopy. One way to follow how excited states evolve is to create them with an electric field or a laser, and then track their decay with a spectroscopic probe. On page 1628 of this issue, Loth et al. (7) show that the tunneling electrons from an STM tip can be used to pump electron-spin excitations. They followed the dynamics of relaxation of this electron spin with atomic-resolution STM imaging that used tunneling electrons with lower energy (see the figure). Their experiment opens up studies of the nanosecond dynamics of individual nanostructures, which has been a goal for surface scientists since the invention of the STM. Time-resolved STM experiments have been performed previously but have lacked spatial resolution (8, 9).