Novel theoretical approach in photoemission spectroscopy: application to isotope effect and boron-doped diamond

TL;DR

This paper introduces a new path-integral theoretical framework for calculating photoemission spectra in correlated electron systems, successfully applied to isotope effects and phase transitions in Bi2212 and boron-doped diamond.

Contribution

It develops a novel path-integral approach for PES calculations and demonstrates its effectiveness on complex materials with electron-phonon interactions.

Findings

Isotopic shift in Bi2212 due to off-diagonal quadratic e-ph coupling

Electron-electron repulsion suppresses isotope effects

Semiconductor-metal transition in BDD driven by e-ph coupling and doping

Abstract

A new path-integral theory is developed to calculate the photoemission spectra (PES) of correlated many-electron systems. The application to the study on Bi2Sr2CaCu2O8 (Bi2212) and boron-doped diamond (BDD) is discussed in details. It is found that the isotopic shift in the angle-resolved photoemission spectra of Bi2212 is due to the off-diagonal quadratic electron-phonon (e-ph) coupling, whereas the presence of electron-electron repulsion partially suppresses this effect. For the BDD, a semiconductor-metal phase transition, which is induced by increasing the e-ph coupling and dopant concentration, is reproduced by our theory. Additionally, the presence of Fermi edge and phonon step-like structure in PES is found to be due to a co-existence of itinerant and localized electronic states in BDD.