Over the last decade, angle-resolved photoemission spectroscopy has emerged as one of the most important experimental tools used in the study of complex materials, with the high-temperature superconductors being one of the most important examples. The improved resolution and carefully matched experiments have turned this technique into a sophisticated many-body spectroscopy. The information from this technique has been crucial in our understanding of high-temperature superconductors. I think this is the main reason why this paper is highly cited.

It describes a wealth of new information made available by a significantly improved experimental method that has been optimized to understand the superconductors.

Complex phenomenon in solids is a major theme of physics in the 21st century. As better controlled model systems evolve, a sophisticated understanding on the universality and diversity of these solids may lead to greater revelations well beyond themselves. The cuprate-based high-temperature superconductor is one of the most important examples of complex solids, where the dramatic quantum phenomenon of superconductivity, i.e. conduction without resistance, occurred at a temperature much higher than previously thought possible. Understanding this phenomenon is one of the holy grails in physics today.

Angle-resolved photoemission spectroscopy is a leading experimental tool to push the frontier of this important field. Some physics of solids are already understood by their macroscopic and thermodynamic properties, but the deepest insights often come from sophisticated spectroscopies. As one of such experiments, angle-resolved photoemission provides what we need the most: the direction, the speed, and the scattering processes of the electrons involved in superconductivity. With extremely high angular and energy resolutions achievable these days, this technique reveals the electronic structure with unprecedented precision and sophistication—information which will form the foundation for a microscopic understanding of the cuprate physics. Our paper provided the most comprehensive and updated description of the wealth of information obtained by this technique, and is most likely the reason why it is highly cited.

I started work on the high-temperature superconductors right after it was discovered while I was a graduate student. Interestingly, my very first paper (which formed the core of my thesis) was also identified by ISI in 1988 as one of the most-cited papers in the field.