Mechanism of gap opening in a triple-band Peierls system: in atomic wires on Si

One dimensional (1D) metals are unstable at low temperature undergoing a metal-insulator transition coupled with a periodic lattice distortion, a Peierls transition. Angle-resolved photoemission study for the 1D metallic chains of In on Si(111), featuring a metal-insulator transition and triple metallic bands, clarifies in detail how the multiple band gaps are formed at low temperature. In addition to the gap opening for a half-filled ideal 1D band with a proper Fermi surface nesting, two other quasi-1D metallic bands are found to merge into a single band, opening a unique but k-dependent energy gap through an interband charge transfer. This result introduces a novel gap-opening mechanism for a multiband Peierls system where the interband interaction is important.

Time-Resolved Electron Energy Loss Spectroscopy

Two recent instrumental improvements in high-resolution electron energy loss spectroscopy make possible the recording of complete surface vibrational spectra on the millisecond time scale. This is the first spectroscopic probe capable of directly measuring fundamental surface rate processes in real time with a resolution less than or equal to 1 millisecond. Such measurements are the key to understanding surface kinetics at the molecular level. This article summarizes experiments on the adsorption and decomposition of formic acid on Cu(100) to investigate the temperature and coverage dependence of the formate intermediate. Other results are cited that provide a detailed description of the decomposition of methanol on Ni(110). Also reported are direct measurements of the residence time of carbon monoxide on Cu(100) and the associated desorption kinetics.

Disorder-induced microscopic magnetic memory

Using coherent x-ray speckle metrology, we have measured the influence of disorder on major loop return point memory (RPM) and complementary point memory (CPM) for a series of perpendicular anisotropy Co/Pt multilayer films. In the low disorder limit, the domain structures show no memory with field cycling--no RPM and no CPM. With increasing disorder, we observe the onset and the saturation of both the RPM and the CPM. These results provide the first direct ensemble-sensitive experimental study of the effects of varying disorder on microscopic magnetic memory and are compared against the predictions of existing theories.