Time-resolved photoemission apparatus achieving sub-20-meV energy resolution and high stability

TL;DR

This paper presents a highly stable, high-resolution time-resolved photoemission apparatus capable of sub-20-meV energy resolution, enabling detailed studies of superconducting and surface states with advanced laser and analyzer technology.

Contribution

The paper introduces a novel setup combining a hemispherical analyzer with a pulsed laser source, achieving unprecedented energy and temporal resolution for time-resolved photoemission measurements.

Findings

Resolved superconducting peaks in cuprates

Demonstrated long-term stability for normalization-free data collection

Achieved sub-20-meV energy resolution with high temporal precision

Abstract

The paper describes a time- and angle-resolved photoemission apparatus consisting of a hemispherical analyzer and a pulsed laser source. We demonstrate 1.48-eV pump and 5.90-eV probe measurements at the >10.5-meV and >240-fs resolutions by use of fairly monochromatic 170-fs pulses delivered from a regeneratively amplified Ti:sapphire laser system operating typically at 250 kHz. The apparatus is capable to resolve the optically filled superconducting peak in the unoccupied states of a cuprate superconductor, Bi2Sr2CaCu2O8+d. A dataset recorded on Bi(111) surface is also presented. Technical descriptions include the followings: A simple procedure to fine-tune the spatio-temporal overlap of the pump-and-probe beams and their diameters; achieving a long-term stability of the system that enables a normalization-free dataset acquisition; changing the repetition rate by utilizing acoustic optical modulator and frequency-division circuit.