Angle-Resolved Photoemission Spectroscopy on High-Temperature Superconductors by Junfeng He

Author:Junfeng He
Language: eng
Format: epub
Publisher: Springer Berlin Heidelberg, Berlin, Heidelberg

The distinct behaviors of the two energy features are further resolved by the temperature-dependent measurements. Shown in Fig. 4.5 is the effective real part of the electron self-energy measured at different temperatures for three typical momentum cuts. It is evident that both the LW and the HI energy features exhibit dramatic superconductivity-induced electron self-energy change upon entering the superconducting state. However, their temperature-dependent behaviors are very different.

First, the coupling strength of the two energy features exhibits strong momentum dependence, as evidenced by the temperature-induced self-energy change [Fig. 4.5g–i]. For the cut 3 near the antinodal region, the superconductivity-induced self-energy change is mainly dominated by the LW energy feature (Fig. 4.5i). When moving to the cut 2, the development of both energy features is clear, but the coupling strength of the LW energy feature appears to get weaker when the momentum moves from the antinodal toward the nodal regions. For the cut 1, there is a large superconductivity-induced self-energy change and an apparent existence of the HI energy feature in the normal state. But it is difficult to disentangle whether such a change is caused by HI or LW energy features because they are too close in energy.

Second, these two energy features show different temperature dependence across T. It is clear from Fig. 4.5g, h that the HI energy feature can be observed at both below and above T. The temperature-induced self-energy change takes off even above T, which indicates that the HI energy feature might be caused by a 70 meV phonon. In contrast, the obvious self-energy enhancement of the LW energy feature occurs well into the superconducting state (such as the data at 50 K and below).

Fig. 4.6Doping dependence of the two energy features. Effective real part of electron self-energy for OD82K sample (a) Opt91K sample (b) and UD89K sample (c). d EDCs at the Fermi momentum k along the cut 18 for samples with different doping levels. e Summary of the momentum dependence of the two energy features. Reprinted with the permission from [20]. Copyright 2013 by the American Physical Society

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