ARPES: A Probe of Electronic Correlations

Abstract

Abstract. Angle-resolved photoemission spectroscopy (ARPES) is one of the most direct methods of studying the electronic structure of solids. By measuring the kinetic energy and angular distribution of the electrons photoemitted from a sample illuminated with sufficiently high-energy radiation, one can gain information on both the energy and momentum of the electrons propagating inside a material. This is of vital importance in elucidating the connection between electronic, magnetic, and chemical structure of solids, in particular for those complex systems which cannot be appropriately described within the independent-particle picture. Among the various classes of complex systems, of great interest are the transition metal oxides, which have been at the center stage in condensed matter physics for the last four decades. Following a general introduction to the topic, we will lay the theoretical basis needed to understand the pivotal role of ARPES in the study of such systems. After a brief overview on the state-of-the-art capabilities of the technique, we will review some of the most interesting and relevant case studies of the novel physics revealed by ARPES in 3d -, 4d -and 5d -based oxides.

Formation of Hubbard-like bands as a fingerprint of strong electron-electron interactions in FeSe

“…These measurements indicate that the low-energy electronic structure broadly resembles that predicted by Density Functional Theory (DFT) calculations, at least, at temperatures above any magnetic or orbital orderings, but with the experimental band dispersions being renormalised by a factor typically of ∼3 [14,15], although this varies substantially between systems, and is orbital-dependent [5]. However, while general considerations of many-body theory would suggest that this band renormalisation must be accompanied by the transfer of spectral weight into incoherent excitations at higher binding energies [17], the high energy spectral weight has only rarely been experimentally investigated in Fe-based superconductors [15,18].…”

“…Methods.-Single crystals of FeSe were grown by the vaportransport method [20]. ARPES measurements were performed at the I05 beamline at Diamond Light Source at temperatures below 10 K. ARPES measurements are a probe of the one-particle spectral function A(ω, k) [17], multiplied by the Fermi occupation function and the matrix elements for photo-emission [17], with some additional background. This spectral function is commonly expressed as: arXiv:1612.02676v1 [cond-mat.supr-con] 8 Dec 2016…”

“…Generally speaking, at higher binding energy, features can become very broad and incoherent when Σ becomes large, and in particular the formation of Hubbardlike bands is possible [32,33]. While experimental evidence of Hubbard bands has been largely reported for effective oneband systems [17,34], results for multiorbital systems are scarce with only a few well-studied exceptions like transition metal oxides [35][36][37][38].…”

Quantitative comparison of LDA+DMFT and ARPES spectral functions

“…2) e-mail: nekrasov@iep.uran.ru 2) e-mail: pavlov@iep.uran.ru and damping associated with electron-electron (or some other) interactions in the system under study. The incident beam energy determines the relative probability of a given electronic state to be excited [1,4]. This significantly affects the relative intensity of various branches of the electronic spectrum on a spectral function map.…”

“…This significantly affects the relative intensity of various branches of the electronic spectrum on a spectral function map. Also, the experimental instrumental resolution (angle and energy resolutions) provides a sizable contribution to the width of the electron bands [4]. Another remarkable contribution to the width and intensity of the electronic spectrum (which is not directly related to the experimental setup) is the finite lifetime of a photo-hole arising in the process of photoemission [1].…”