Unoccupied electronic states in atomic chains on Si(557)-Au: Time-resolved two-photon photoemission investigation

Abstract

The prototypical one-dimensional Si͑557͒-Au surface is investigated with time-resolved two-photon photoemission. Three new states are found near ⌫ , two of them in the band gap of silicon. These states cannot be explained by existing band calculations. As a possible solution, we suggest a closer examination of the atomic and electronic structure near the step edge.

Unoccupied electronic structure and momentum-dependent scattering dynamics in Pb/Si(557) nanowire arrays

“…Based on their results, electrons 3 eV above E F , which are under discussion here, should exhibit lifetimes shorter than 5 fs. Similar small lifetimes were obtained in other nanoscale systems on different substrates, such as atomic Au wires on Si(557) [31], Bi films on Cu(111) [48], epitaxial Ag films on MgO(100) [49], or Pb quantum-well states on Cu(111) [16].…”

“…Figure 8 summarizes our experimental findings on the occupied and unoccupied electronic structure and indicates the near-resonant excitation pathways of states A and B. The relevant initial state at E − E F = −0.43 eV is the Si valence-band maximum, and it was also observed in DFT calculations on the Pb/Si(111) system [42] as well as in experimental studies on Au/Si(557) [31] and Au/Si(553) [32].…”

“…While pump-induced melting of CDWs in layered crystals has been investigated in the time domain using femtosecond optical [25], time-and angle-resolved direct photoemission [26,27], and transmission electron diffraction [28,29] pump-probe methods, the investigation of photoinduced melting of CDWs on 1D surface reconstructions has so far been limited to surface-sensitive electron diffraction [30]. Rügheimer et al have published a first time-resolved 2PPE study of the one-dimensional Si(557)-Au atomic chain system [31]. That work reported three electronic states, which were absent in electronic structure calculations.…”

Spin-split silicon states at step edges of Si(553)-Au

“…2,20 The sample preparation was optimized by low-energy electron diffraction (LEED). Figure 2 shows a diffraction pattern with faint half-and third-order horizontal streaks which are characteristic of the (1 × 2) and (1 × 3) reconstruction of the gold chains and step-edge atoms, respectively.…”

“…This concept can also explain the observation of states of odd symmetry on the Si(557)-Au surface, which had not been understood before. 20 The odd symmetry of peak D could also be explained by bulk transitions from initial states near the VBM where the heavy-hole band splits into states with even and odd symmetry with repsect to the mirror plane.…”