Excited electron-bubble states in superfluid helium-4: a time-dependent density functional approach

TL;DR

This study uses a time-dependent density functional approach to analyze excited electron-bubble states in superfluid helium-4, comparing two computational methods and predicting their spectroscopic behavior, while clarifying the stability of certain bubble states.

Contribution

It introduces and compares two different density functional methods for simulating excited electron-bubbles in helium-4, establishing their applicability and limitations.

Findings

Finite-range functional accurately models 1P bubble absorption spectra.

Zero-range functional effectively simulates real-time evolution of 2P bubbles.

Metastable 2P electron-bubbles are not physically realizable.

Abstract

We present a systematic study on the excited electron-bubble states in superfluid helium-4 using a time-dependent density functional approach. For the evolution of the 1P bubble state, two different functionals accompanied with two different time-development schemes are used, namely an accurate finite-range functional for helium with an adiabatic approximation for electron versus an efficient zero-range functional for helium with a real-time evolution for electron. We make a detailed comparison between the quantitative results obtained from the two methods, which allows us to employ with confidence the optimal method for suitable problems. Based on this knowledge, we use the finite-range functional to calculate the time-resolved absorption spectrum of the 1P bubble, which in principle can be experimentally determined, and we use the zero-range functional to real-time evolve the 2P bubble for several hundreds of picoseconds, which is theoretically interesting due to the break down of adiabaticity for this state. Our results discard the physical realization of relaxed, metastable 2P electron-bubbles