Local electron-electron interaction strength in ferromagnetic nickel determined by spin-polarized positron annihilation.

Josef Andreas Weber,Diana Benea,Christoph Hugenschmidt,Hubert Ceeh,Dieter Vollhardt,Jan Minár,Liviu Chioncel,Hubert Ebert,Michael Leitner,Peter Böni

doi:10.1038/srep20898

Abstract

We employ a positron annihilation technique, the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR), to measure the spin-difference spectra of ferromagnetic nickel. The experimental data are compared with the theoretical results obtained within a combination of the local spin density approximation (LSDA) and the many-body dynamical mean-field theory (DMFT). We find that the self-energy defining the electronic correlations in Ni leads to anisotropic contributions to the momentum distribution. By direct comparison of the theoretical and experimental results we determine the strength of the local electronic interaction U in ferromagnetic Ni as 2.0 ± 0.1 eV.

Highlights

Theoretical results obtained with LSDA + DMFT can be compared with experimental data obtained, for example, by photoemission spectroscopy (PES)
We show that by combining experimental results of the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR) with LSDA + DMFT computations including a careful and realistic treatment of the positron probe effects, it is possible to determine the strength of the electronic interactions in Ni quite unambiguously
The central plot represents the measured spectra, and is surrounded by theoretical results obtained from LSDA + DMFT performed for several values of U

Summary

Introduction

Theoretical results obtained with LSDA + DMFT can be compared with experimental data obtained, for example, by photoemission spectroscopy (PES). This technique measures spectral functions, i.e., the imaginary part of the one-particle Green function, and determines correlation induced shifts of the spectral. We show that by combining experimental results of the spin-polarized two-dimensional angular correlation of annihilation radiation (2D-ACAR) with LSDA + DMFT computations including a careful and realistic treatment of the positron probe effects, it is possible to determine the strength of the electronic interactions in Ni quite unambiguously

Methods

Results

Conclusion