Phase-Controlled Ramsey Interference of XUV Photoelectrons

TL;DR

This paper demonstrates phase-controlled quantum interference in XUV photoelectron spectra, revealing how interference fringes depend on pulse delay, phase, and intensity, with implications for ultrafast electron dynamics.

Contribution

It introduces a comprehensive analysis of Ramsey interference in XUV photoionization, linking fringe patterns to phase accumulation, Stark shifts, and bound-state dynamics.

Findings

Interference fringes depend linearly on the relative phase and inversely on delay time.

Modulations originate from quantum interference, not Autler--Townes splitting.

Bound-state dynamics and Stark shifts control interference contrast.

Abstract

We investigate Ramsey-type quantum interference in photoelectron momentum distributions generated by two time-delayed, linearly polarized extreme-ultraviolet (XUV) laser pulses. The electron dynamics are studied by solving the full-dimensional time-dependent Schr\"odinger equation within the single-active-electron approximation for neon initially prepared in a current-carrying $2p_+$ state. The coherent superposition of electron wave packets released by the two pulses gives rise to pronounced interference fringes in both energy-resolved spectra and angle-resolved momentum distributions. We demonstrate that the fringe positions are governed by a Ramsey phase accumulated during the interpulse delay, resulting in a linear dependence on the relative carrier-envelope phase and an inverse scaling of the fringe spacing with the delay time. By systematically varying the laser intensity, we establish that the observed modulations originate from temporal quantum interference rather than Autler--Townes splitting. Analysis of the time-resolved bound-state population dynamics reveals that carrier-envelope-phase dependent bound--bound coupling dominated by transient population transfer to the $2s$ state, which controls the interference contrast. The accumulated phase is further interpreted in terms of a dynamic Stark shift of the dressed bound states, which is quantitatively reproduced using a reduced two-level model.