Parametric excitation of an optically silent Goldstone-like phonon mode

TL;DR

This paper demonstrates a novel mechanism to coherently excite silent Goldstone-like phonon modes in hexagonal manganites through nonlinear coupling with infrared-active Higgs-like modes, enabling control over previously inaccessible phonons.

Contribution

It introduces a new method for coherently exciting silent Goldstone-like phonon modes via nonlinear coupling with Higgs-like modes, supported by first-principles and phenomenological modeling.

Findings

Silent Goldstone-like phonons can be coherently excited.

Nonlinear coupling enables control of otherwise inaccessible phonons.

The mechanism is demonstrated through theoretical modeling.

Abstract

It has recently been indicated that the hexagonal manganites exhibit Higgs- and Goldstone-like phonon modes that modulate the amplitude and phase of their primary order parameter. Here, we describe a mechanism by which a silent Goldstone-like phonon mode can be coherently excited, which is based on nonlinear coupling to an infrared-active Higgs-like phonon mode. Using a combination of first-principles calculations and phenomenological modeling, we describe the coupled Higgs-Goldstone dynamics in response to the excitation with a terahertz pulse. Besides theoretically demonstrating coherent control of crystallographic Higgs and Goldstone excitations, we show that the previously inaccessible silent phonon modes can be excited coherently with this mechanism.