Photoemission Line shape Study on La$_{0.7}$Sr$_{0.3}$Mn$_{1-\delta}$Al$_\delta$O$_{3}$ ($\delta$ = 0, 0.03, 0.06)

TL;DR

This study investigates whether extrinsic image charge screening significantly affects photoemission spectra in La$_{0.7}$Sr$_{0.3}$Mn$_{1- ext{delta}}$Al$_{ ext{delta}}$O$_3$ compounds, finding it has minimal impact contrary to previous theoretical predictions.

Contribution

The paper provides experimental evidence that challenges the previously suggested strong influence of extrinsic image charge effects on photoemission spectra in poorly conducting materials.

Findings

Photoemission line shapes do not change as predicted by the extrinsic image force theory.

Experimental spectra show minimal influence of long-range Coulomb interactions.

Results suggest intrinsic density of states are reliably observed without significant extrinsic distortion.

Abstract

We have studied the line shapes of ultraviolet photoemission spectra of La$_{0.7}$Sr$_{0.3}$Mn$_{1-\delta}$Al$_\delta$O$_3$ ($\delta$ = 0, 0.03, 0.06) systems to test the extrinsic image charge screening effect on photoemission spectra recently suggested by R. Joynt (Science {\bf 284}, 777 (1999)), who argued that the photoemission spectrum near the Fermi energy, specially for poorly conducting system, can be very different from the intrinsic density of states because the outgoing electron has probability of losing its kinetic energy due to the image force. We tested this argument in real materials experimentally by measuring the photoemission line shapes of La$_{0.7}$Sr$_{0.3}$Mn$_{1-\delta}$Al$_\delta$O$_3$ systems, for which all the requirements of this theory are satisfied and sample resistivities change systematically. We found that experimental photoemission spectra do not show the change of line shapes expected from the extrinsic image force effect and we conclude that the influence of this long range interaction is not so large as suggested in that paper.