Low-energy (< 10 meV) feature in the nodal electron self-energy and strong temperature dependence of the Fermi velocity in Bi(2)Sr(2)CaCu(2)O(8+delta)

TL;DR

This study reveals a new low-energy kink in the electron self-energy of Bi2212 that is temperature-dependent, significantly affecting the Fermi velocity near the Fermi energy, with implications for understanding high-temperature superconductivity.

Contribution

The paper identifies a novel low-energy feature in the electron self-energy of Bi2212 that varies with temperature, distinct from the well-known higher-energy kink.

Findings

A new kink-like feature appears less than 10 meV below E_F.

The low-energy kink is strongest below the superconducting transition temperature.

The Fermi velocity increases by nearly 30% between 70 K and 110 K.

Abstract

Using low-photon energy angle-resolved photoemission (ARPES), we study the low-energy dispersion along the nodal (pi, pi) direction in Bi(2)Sr(2)CaCu(2)O(8+delta) (Bi2212) as a function of temperature. Less than 10 meV below the Fermi energy, the high-resolution data reveals a novel "kink"-like feature in the real part of the electron self-energy that is distinct from the larger well-known kink roughly 70 meV below E_F. This new kink is strongest below the superconducting critical temperature and weakens substantially as the temperature is raised. A corollary of this finding is that the Fermi velocity, as measured over this energy range, varies rapidly with temperature - increasing by almost 30% from 70 to 110 K.