Deconstructing the Hubbard Hamiltonian by Ultrafast Quantum Modulation Spectroscopy in Solid-state Mott Insulators

TL;DR

This paper introduces quantum modulation spectroscopy, a novel technique to explicitly probe and deconstruct the Hubbard Hamiltonian in Mott insulators by driving specific microscopic degrees of freedom with light.

Contribution

It demonstrates a new experimental method to directly observe how individual modes affect correlated electron transport in Mott insulators.

Findings

Sidebands in optical spectrum reveal mode-specific renormalizations.

Asymmetry observed between doublon and holon renormalizations.

Method applicable to various materials for detailed Hamiltonian analysis.

Abstract

Most available theories for correlated electron transport are based on the Hubbard Hamiltonian. In this effective theory, renormalized hopping and interaction parameters only implicitly incorporate the coupling of correlated charge carriers to microscopic degrees of freedom. Unfortunately, no spectroscopy can individually probe such renormalizations, limiting the applicability of Hubbard models. We show here that the role of each individual degree of freedom can be made explicit by using a new experimental technique, which we term 'quantum modulation spectroscopy' and we demonstrate here in the one-dimensional Mott insulator ET-F2TCNQ. We explore the role on the charge hopping of two localized molecular modes, which we drive with a mid infrared optical pulse. Sidebands appear in the modulated optical spectrum, and their linshape is fitted with a model based on the dynamic Hubbard Hamiltonian. A striking asymmetry between the renormalization of doublons and holons is revealed. The concept of quantum modulation spectroscopy can be used to systematically deconstruct Hubbard Hamiltonians in many materials, exposing the role of any mode, electronic or magnetic, that can be driven to large amplitude with a light field.