# Origin of the crossover from polarons to Fermi liquids in transition metal oxides

## TL;DR

This paper investigates the transition from polaronic to Fermi liquid behavior in doped transition metal oxides, revealing a universal mechanism driven by non-adiabatic electron-phonon interactions based on ab initio calculations.

## Contribution

It demonstrates that the polaron to Fermi liquid crossover in TMOs is caused by non-adiabatic polar electron-phonon coupling, providing a new understanding of carrier behavior in these materials.

## Key findings

- Transition from polaronic liquid to Fermi liquid with doping.
- Transition driven by plasma oscillation frequency surpassing phonon frequency.
- Universal mechanism underlying polaron formation in TMOs.

## Abstract

Transition metal oxides (TMOs) host a wealth of exotic phenomena ranging from charge, orbital, and magnetic order to nontrivial topological phases and superconductivity. In order to translate these unique materials properties into novel device functionalities, TMOs must be doped. However, the nature of carriers in doped oxides and their conduction mechanism at the atomic scale remain unclear. Recent angle-resolved photoelectron spectroscopy (ARPES) investigations provided new insight into these questions, revealing that the carriers of prototypical metal oxides undergo a transition from a polaronic liquid to a Fermi liquid regime with increasing doping. Here, by performing \textit{ab initio} many-body calculations of the ARPES spectra of TiO$_2$, we show that this transition originates from non-adiabatic polar electron-phonon coupling, and occurs when the frequency of plasma oscillations exceeds that of longitudinal-optical phonons. This finding suggests that a universal mechanism may underlie polaron formation in TMOs, and provides a new paradigm for engineering emergent properties in quantum matter.