Numerical study of the isotope effect in underdoped high-temperature superconductors: Calculation of the angle-resolved photoemission spectra

TL;DR

This study uses Diagrammatic Monte Carlo to analyze how isotope substitution affects the angle-resolved photoemission spectra in undoped cuprates, revealing energy-momentum dependent anomalies and detailed spectral changes.

Contribution

It provides the first systematic numerical analysis of isotope effects on ARPES in cuprates using a sign-problem-free Monte Carlo approach.

Findings

Isotope effect varies strongly with energy and momentum.

Anomalous enhancement of isotope effect in intermediate coupling regime.

Predicted detailed changes in ARPES lineshape due to isotope substitution.

Abstract

We present a numerical study of the isotope effect on the angle resolved photoemission spectra (ARPES) in the undoped cuprates. By the systematic-error-free Diagrammatic Monte Carlo method, the Lehman spectral function of a single hole in the tt't''-J model in the regime of intermediate and strong couplings to optical phonons is calculated for normal and isotope substituted systems. We found that the isotope effect is strongly energy-momentum dependent, and is anomalously enhanced in the intermediate coupling regime while it approaches to that of the localized hole model in the strong coupling regime. We predict the strengths of effect as well as the fine details of the ARPES lineshape change. Implications to the doped case are also discussed.