09:00-10:40 | We1: E-ph coupling in novel 2D materials (I) |
10:40-11:20 | Coffee break |
11:20-13:00 | We2: E-ph coupling in novel 2D materials (II) |
13:00-15:30 | Poster session B |
Afternoon off - some suggested activities can be found here | |
19:30-20:30 | Public lecture by Polanyi in Kutxa Sala Andia (city center) |
Chair: J. Wells, Trondheim, Norway
Contributed talk
Importance of momentum resolved electron-phonon coupling in analysis of inelastic tunneling and photoemission spectroscopy
1International Center for Materials Nanoarchitectonics, National Institute for Materials Sciences, Japan
2Department of Materials Engineering, the University of Tokyo, Japan
3Department of Advanced Materials Science, the University of Tokyo, Japan
Electron phonon coupling (EPC) plays a crucial role in determining the range of the electronic thermal diffusion for the femtosecond laser pulse excitation, forming the charge density waves, cooper-pair creation in superconductivity, etc. The EPC has been mostly analyzed through the momentum-averaged description such as the Eliashberg function. While such rather simplified description has successfully served a basis for intuitive understanding the above phenomena, it is often not sufficient to analyze the low-dimensional system and high-resolved experimental data.
In this study, we found that calculating the momentum resolved EPC is requisite for analysis of both the inelastic tunneling spectroscopy with STM (STM-IETS) [1] and inelastic photoemission spectroscopy (IEPES) [2], which are surface vibrational spectroscopic tools based on the inelastic process of the electron at the solid surfaces. The spectrum of the STM-IETS experiments for the Cu(110) surfaces shows a peak at 6 meV, while that of the IEPES for the same surface shows a step structure arising from the phonon excitation at 14.7 meV. The momentum resolved EPC that is described by the matrix element of the interband transition of the electron with transferring the energy and momentum to the phonon can be evaluated from ab-initio calculations. While the above characteristic energy does not appear in the phonon density of states straightforwardly, the density functional perturbation theory calculations show the strong peak at around 6.2 meV in the EPC spectrum for the electron near the Fermi level at the Γ point and at 14.5 meV for the electron just above the vacuum level at the Y point. Although the elementary processes of the inelastic tunneling and photoemission are different, the momentum resolved EPC calculations effectively work for describing the selectivity of the phonon excitation from among many possible phonon modes in both inelastic processes.
[1] R. Arafune et al., in preparation
[2] E. Minamitani et al., Phys. Rev. B 88, 224301 (2013)