Attosecond Transient Absorption Spectroscopy of Strongly Correlated Mott Insulators: Signature of the Creation and Annihilation of Double Occupancy

TL;DR

This study uses attosecond transient absorption spectroscopy to explore ultrafast electron dynamics in Mott insulators, revealing correlation-driven spectral features related to double occupancy creation and annihilation.

Contribution

It provides the first detailed observation of correlation-driven spectral signatures in Mott insulators using attosecond spectroscopy.

Findings

Unconventional spectra in Mott insulators differ from band insulators.

Negative difference absorption indicates electron correlation effects.

Spectral features linked to double occupancy dynamics.

Abstract

We applied the time-resolved attosecond transient absorption spectroscopy to systematically investigate ultrafast optical responses of condensed matter systems. Under an intense pump pulse, absorption spectra indicate that the non-interacting electrons of band insulators produce a field-induced redshift, known as the dynamical Franz-Keldysh effect, as commonly expected. In contrast to the band insulators, in Mott insulators, unconventional spectra are observed which do not fully reflect the dynamical Franz-Keldysh effect. While it still exhibits the fishbone-like structures mimicking the dynamical Franz-Keldysh effect, the spectra show a negative difference absorption below the band edge, rendering a blueshift. In addition, the decomposed difference absorption reveals the creation and the annihilation of double occupancy mainly contribute to the negative signal, implying that the unconventional spectra are purely driven by the electron-correlations. These demonstrations of unconventional responses would guide us to the correlation-embedded attosecond electron dynamics in condensed matter systems.