Transient Work Function Gating: A New Photoemission Regime

TL;DR

This paper introduces transient work function gating (TWFG), a novel photoemission regime that actively modulates the work function to achieve near-threshold photoelectrons with improved emittance, efficiency, and temporal control, enabling advances in electron and x-ray sources.

Contribution

The paper presents the theoretical foundation of TWFG, a new method to control photoemission by dynamically gating the work function using optical fields, overcoming traditional trade-offs.

Findings

TWFG can produce near-threshold photoelectrons with thermally limited emittance.

It achieves percent-level quantum efficiency.

It offers control over temporal coherence in photoemission.

Abstract

We present the theoretical basis for a new photoemission regime, transient work function gating (TWFG), that temporally and energetically gates photoemission and produces near-threshold photoelectrons with thermally limited emittance, percent-level quantum efficiency, and control over temporal coherence. The technique consists of actively gating the work function of a generalized photocathode using non-ionizing long-wavelength optical field to produce an adiabatic modulation of the carrier density at their surface. We examine TWFG as a means to circumvent the long-standing trade-off between low emittance and high quantum efficiency, untethered to particle source or photocathode specifics. TWFG promises new opportunities in photoemission physics for next generation electron and accelerator-based x-ray photon sources.