Photoemission Studies of Copper and Silver: Experiment

Berglund, C. N.; Spicer, W. E.

doi:10.1103/physrev.136.a1044

Cited by 429 publications

(130 citation statements)

References 24 publications

Supporting

Mentioning

117

Contrasting

Unclassified

Order By: Relevance

“…Indeed, as shown in Fig. 3C, we verified experimentally that the assumption of a momentum-averaged Coulomb matrix element M is valid, as originally suggested by Berglund and Spicer (44). Similar models have also been successfully used to explain the hot-electron lifetimes of intermediate states measured using time-resolved two-photon photoemission (Tr-2PPE) (6, 46).…”

Section: Discussionsupporting

confidence: 56%

“…Although the focus of this work is on photoelectron lifetimes in the high-energy >20-eV region, a comparison with Tr-2PPE data allows us to gain valuable physical insights. In general, electron-electron Coulomb interactions are energydependent due to different screening properties at different energies in a material (44). Here, for convenience, we assume the Coulomb matrix element M is a constant and select values by fitting to the experimental data.…”

Section: Discussionmentioning

confidence: 99%

“…Assuming ρ ↑ = ρ ↓ = ρ and M ↑↑ = M ↑↓ = M, Eq. 1 is simply reduced to 1 τðEÞ = 2π Z ρ 3 jMj 2 ðE − E F Þ 2 , which is the well-known ðE − E F Þ −2 scaling of hot-electron lifetimes excited close to the E F (44).…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Distinguishing attosecond electron–electron scattering and screening in transition metals

Chen

Tao

Carr

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Electron-electron interactions are the fastest processes in materials, occurring on femtosecond to attosecond timescales, depending on the electronic band structure of the material and the excitation energy. Such interactions can play a dominant role in light-induced processes such as nano-enhanced plasmonics and catalysis, light harvesting, or phase transitions. However, to date it has not been possible to experimentally distinguish fundamental electron interactions such as scattering and screening. Here, we use sequences of attosecond pulses to directly measure electronelectron interactions in different bands of different materials with both simple and complex Fermi surfaces. By extracting the time delays associated with photoemission we show that the lifetime of photoelectrons from the d band of Cu are longer by ∼100 as compared with those from the same band of Ni. We attribute this to the enhanced electron-electron scattering in the unfilled d band of Ni. Using theoretical modeling, we can extract the contributions of electron-electron scattering and screening in different bands of different materials with both simple and complex Fermi surfaces. Our results also show that screening influences high-energy photoelectrons (≈20 eV) significantly less than low-energy photoelectrons. As a result, high-energy photoelectrons can serve as a direct probe of spin-dependent electron-electron scattering by neglecting screening. This can then be applied to quantifying the contribution of electron interactions and screening to low-energy excitations near the Fermi level. The information derived here provides valuable and unique information for a host of quantum materials.attosecond science | high harmonic generation | ARPES | electron-electron interactions E xcited-state electron dynamics in materials play a critical role in light-induced phase transitions in magnetic and charge density wave materials, in superdiffusive spin flow, in catalytic processes, and in many nano-enhanced processes. However, to date exploring such dynamics is challenging both experimentally and theoretically. Using femtosecond lasers in combination with advanced spectroscopies, it is possible to measure the lifetime of excited charges and spins directly in the time domain (1). To date, such studies have been applied to a wide variety of materials, including noble metals and semiconductors (1-4), ferromagnetic metals (5-8), strongly correlated materials (9) and high-T c superconductors (10, 11). These studies have significantly improved our understanding of the fastest coupled interactions and relaxation mechanisms in matter. However, to date experimental investigations of electron dynamics have been limited to femtosecond timescale processes in materials with low charge densities (9-12) or to Fermi-liquid metals with low excitation energies (<3.0 eV above E F , where E F is the Fermi energy) (3-5), due to the visible-to-UVwavelength photon energies used in these experiments. In this region, two fundamental electron interactions-electron-electron sc...

show abstract

Section: Discussionsupporting

confidence: 56%

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

Distinguishing attosecond electron–electron scattering and screening in transition metals

Chen

Tao

Carr

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

show abstract

“…In our previous work [9], the QE was computed using the free electron gas model of a metal and used the FermiDirac distribution for the electron density of states [10]. This derivation of QE assumed the electrons are at zero temperature and imposed the requirement that the Figure 6 compares measurements after H-ion cleaning with the Eqn.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

In-Situ Cleaning of Metal Cathodes using a Hydrogen Ion Beam

Dowell¹,

King²,

Kirby³

et al. 2006

View full text Add to dashboard Cite

Improving and maintaining the quantum efficiency (QE) of a metal photocathode in an s-band RF gun requires a process for cleaning the surface. In this type of gun, the cathode is typically installed and the system is vacuum baked to ~200degrees C. If the QE is too low, the cathode is usually cleaned with the UV-drive laser. While laser cleaning does increase the cathode QE, it requires fluences close to the damage threshold and rastering the small diameter beam, both of which can produce nonuniform electron emission and potentially damage the cathode. This paper investigates the efficacy of a lowenergy hydrogen ion beam to produce high-QE metal cathodes. Measurements of the QE vs. wavelength, surface contaminants using x-ray photoelectron spectroscopy and surface roughness were performed on a copper sample, and the results showed a significant increase in QE after cleaning with a 1keV hydrogen ion beam. The H-ion beam cleaned an area approximately 1cm in diameter and had no effect on the surface roughness while significantly increasing the QE. These results and a comparison with theory as well as a scheme for installing an H-ion cleaner on an s-band gun are presented.

show abstract

“…This was first shown by Berglund and Spicer in 1964 when they identified the 3d DOS in Ag and Cu. 43,44,45 The electronic states in dispersive valence bands are well defined in both energy and momentum. Because momentum is conserved in optical excitation during the photoemission process, one can consider attempting to measure both the binding energy and momentum, or k vector, of the electronic states in the valence bands.…”

Section: Angular Resolutionmentioning

confidence: 99%

A New Spin on Photoemission Spectroscopy

Jozwiak

2008

View full text Add to dashboard Cite

Professor Alessandra Lanzara, ChairThe electronic spin degree of freedom is of general fundamental importance to all matter.Understanding its complex roles and behavior in the solid state, particularly in highly correlated and magnetic materials, has grown increasingly desirable as technology demands advanced devices and materials based on ever stricter comprehension and control of the electron spin. However, direct and efficient spin dependent probes of electronic structure are currently lacking.Angle Resolved Photoemission Spectroscopy (ARPES) has become one of the most successful experimental tools for elucidating solid state electronic structures, bolstered by continual breakthroughs in efficient instrumentation. In contrast, spin-resolved photoemission spectroscopy has lagged behind due to a lack of similar instrumental advances. The power of photoemission spectroscopy and the pertinence of electronic spin in the current research climate combine to make breakthroughs in Spin and Angle Resolved Photoemission Spectroscopy (SARPES) a high priority .This thesis details the development of a unique instrument for efficient SARPES and represents a radical departure from conventional methods. A custom designed spin polarimeter based on low energy exchange scattering is developed, with projected efficiency gains of two orders of magnitude over current state-of-the-art polarimeters. For energy analysis, the 1 popular hemispherical analyzer is eschewed for a custom Time-of-Flight (TOF) analyzer offering an additional order of magnitude gain in efficiency. The combined instrument signifies the breakthrough needed to perform the high resolution SARPES experiments necessary for untangling the complex spin-dependent electronic structures central to today's condensed matter physics.

show abstract

Photoemission Studies of Copper and Silver: Experiment

Cited by 429 publications

References 24 publications

Distinguishing attosecond electron–electron scattering and screening in transition metals

Distinguishing attosecond electron–electron scattering and screening in transition metals

In-Situ Cleaning of Metal Cathodes using a Hydrogen Ion Beam

A New Spin on Photoemission Spectroscopy

Contact Info

Product

Resources

About