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An angle-resolved photoemission spectroscopy study of T1₂Ba₂ CuO₆+[delta] Mottershead, Jeffrey Daniel Frederick

Abstract

Recent angle-resolved photoemission spectroscopy (ARPES) results on the high-temperature superconductor (HTSC) Tl₂Ba₂CuO₄+[sub Δ] (T12201) are presented. A very overdoped sample with a T[sub c] of 30 K was found to have a Fermi surface consisting of a large hole pocket centered at (Π,Π), which is approaching a topological transition. A superconducting gap consistent with a d[sub x[sup 2]-y[sup 2]] order parameter was detected. In contrast with the underdoped HTSCs, where the quasiparticle (QP) linewidth at the top of the band is maximal in the antinodal direction and minimal in the nodal direction, overdoped T12201 was revealed to have a reverse nodal/antinodal anisotropy, with sharp QP peaks in the antinodal region and broader peaks in the antinodal region. The T12201 results establish T12201 as a valuable material for exploring the overdoped side of the phase diagram with ARPES. They also raise numerous questions that demand further ARPES measurements over a broader range of dopings, as well as temperature-dependent measurements. In parallel with the T12201 research, a new in-house ARPES system is being constructed at University of British Columbia (UBC). The ARPES system under construction at UBC incorporates a molecular beam epitaxy (MBE) system for the growth of a much broader range of materials than can typically be studied by ARPES. Novel design techniques to improve the accuracy of ARPES measurements are presented.

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