Surface electronic structures of ferromagnetic Ni(111) studied by STM and angle-resolved photoemission

Abstract

Spin-polarized surface electronic states in Ni͑111͒ have been examined using scanning tunneling microscopy ͑STM͒ and spectroscopy ͑STS͒ combined with high-resolution angle-resolved photoemission spectroscopy ͑HR-ARPES͒. Standing waves derived from the majority-spin Shockley surface state ͑SS͒ have been observed in the STM and dI / dV images. The fast Fourier transform ͑FFT͒-dI / dV image at a different sample bias exhibited a circular contour in the reciprocal space. The radius of the FFT-dI / dV image was in agreement with that of the corresponding constant-energy contour given by the HR-ARPES. The majority-spin Shockley SS is partially occupied and disperses upward, crossing the Fermi level ͑E F ͒ at a wave number of k F = 0.081Ϯ 0.005 Å −1 . The effective mass ͑m ‫ء‬ ͒ with respect to the free-electron mass ͑m e ͒ of the majority-spin Shockley SS was evaluated to be m ‫ء‬ / m e = 0.19Ϯ 0.03. The STS spectrum indicated a pair of the Shockley SS below and above E F with an exchange splitting of ϳ190 meV. By the line-shape analyses of the HR-ARPES spectrum, the lifetime broadening at the ⌫ point was calculated to be 53.6 meV, which agrees well with the width ͑49 meV͒ of the steplike structure in the STS spectrum. The results from the STM/STS and HR-ARPES experiments were found to be mutually consistent.

Exchange splitting of the threeΓ¯surface states of Ni(111) from three-dimensional spin- and angle-resolved photoemission spectroscopy

“…The present value for the exchange splitting coincides with a splitting as observed with STM/STS, where Braun and Rieder found surface locations with two coexistent Shockley type surface states split by 60±15 meV [4]. Notably this is the only such observation to date, where earlier [20] and very recent [7] experiments found no such splitting. The STS measurements by Nishimura et al do not show a 60 meV splitting, instead, they also propose an occupied majority and the unoccupied minority state at 4 K, exchange split by ≈ 190 meV to display in step-like structures in the STS spectra [7].…”

“…Notably this is the only such observation to date, where earlier [20] and very recent [7] experiments found no such splitting. The STS measurements by Nishimura et al do not show a 60 meV splitting, instead, they also propose an occupied majority and the unoccupied minority state at 4 K, exchange split by ≈ 190 meV to display in step-like structures in the STS spectra [7].…”

“…Though, this splitting was not present everywhere on the surface, and its Fermi vectors did not correspond to the previous inverse photoemission [3] nor photoemission experiments [5]. Also, spin integrated state of the art high resolution photoemission [6] and corresponding scanning probe experiments did not resolve this issue [7]. In particular it could not be decided whether the surface states are exchange split or not.…”

In situ visualization of Ni–Nb bulk metallic glasses phase transition

“…The best correspondence was found for hexagonal structure and metastable surface reconstruction (3 × 3)−Ni(111). It is well known that the free-electron-like surface states, the Shockley surface states (SS), are present on the Ni(111) surface [29,30,31]. If the observed in our experiments hexagonal surface structure ( Fig.…”

Spin-Dependent Electron Scattering at Graphene Edges on Ni(111)

“…1(c)], which split into spin-polarized gapped bands G ↑=↓ u=l due to the strong hybridization with Ni d bands [13,14,[19][20][21]. The spin-split Ni d bands can be clearly identified as the two sharp peaks d ↑ and d ↓ in the impurity spectrum; on the Ni surface such peaks are masked by the dominant contribution of surface states, which we label as S 1 and S 2 following the nomenclature of previous studies [22][23][24] (further information on the electronic structure of the surface states can be found in Fig. S2 of the Supplemental Material [19]).…”