Coherent Modulation of the YBa2Cu3O6+x Atomic Structure by Displacive Stimulated Ionic Raman Scattering

TL;DR

This paper explores how Stimulated Ionic Raman Scattering coherently modulates the atomic structure of YBa2Cu3O6+x, revealing its potential role in enhancing superconductivity through resonant phonon excitation.

Contribution

It introduces the mechanism of ionic Raman scattering driven by anharmonic coupling and demonstrates its experimental observation in YBa2Cu3O6+x with implications for superconductivity.

Findings

Coherent oscillations of four symmetric Raman modes observed.

Resonant excitation at 20 THz influences superconducting properties.

Critical assessment of phonon role in superconductivity enhancement.

Abstract

We discuss the mechanism of coherent phonon generation by Stimulated Ionic Raman Scattering, a process different from conventional excitation with near visible optical pulses. Ionic Raman scattering is driven by anharmonic coupling between a directly excited infrared-active phonon mode and other Raman modes. We experimentally study the response of YBa2Cu3O6+x to the resonant excitation of apical oxygen motions at 20 THz by mid-infrared pulses, which has been shown in the past to enhance the interlayer superconducting coupling. We find coherent oscillations of four totally symmetric (Ag) Raman modes and make a critical assessment of the role of these oscillatory motions in the enhancement of superconductivity.