Quantum interference between charge excitation paths in a solid state Mott insulator

TL;DR

This study observes quantum interference effects in charge excitations within a solid state Mott insulator, revealing ultrafast electronic dynamics driven by photo-excitation and quantum coherence.

Contribution

It demonstrates the direct measurement of quantum interference between charge excitation paths in a solid Mott insulator using ultrafast spectroscopy.

Findings

Observation of a 25 THz oscillation in the Mott gap resonance.

Reproduction of oscillations through time-dependent simulations.

Identification of quantum interference between bound and ionized holon-doublon pairs.

Abstract

The competition between electron localization and de-localization in Mott insulators underpins the physics of strongly-correlated electron systems. Photo-excitation, which re-distributes charge between sites, can control this many-body process on the ultrafast timescale. To date, time-resolved studies have been performed in solids in which other degrees of freedom, such as lattice, spin, or orbital excitations come into play. However, the underlying quantum dynamics of bare electronic excitations has remained out of reach. Quantum many-body dynamics have only been detected in the controlled environment of optical lattices where the dynamics are slower and lattice excitations are absent. By using nearly-single-cycle near-IR pulses, we have measured coherent electronic excitations in the organic salt ET-F2TCNQ, a prototypical one-dimensional Mott Insulator. After photo-excitation, a new resonance appears on the low-energy side of the Mott gap, which oscillates at 25 THz. Time-dependent simulations of the Mott-Hubbard Hamiltonian reproduce the oscillations, showing that electronic delocalization occurs through quantum interference between bound and ionized holon-doublon pairs.