New Article in 'Physical Review Letters': Launching Coherent Acoustic Phonon Wave Packets with Local Femtosecond Coulomb Forces

Summary: 

Terahertz light can induce femtosecond force pulses on surfaces when it is focused onto the tip of a scanning tunneling microscope. The force pulses act as a “nano hammer” that launches coherent acoustic phonon wave packets into the material.

Typically, ultrafast lasers are used to excite acoustic phonons in materials by rapid heating of micrometer-sized areas. By contrast, the terahertz-induced phonon excitation uses the Coulomb interaction between tip and material surface. It doesn’t require heating and can be localized to a few nanometers.

Buried interfaces and defects reflect the phonon wave packets, creating a detectable beating of the surface. This enables depth-sensitive phonon nanoscopy akin to sonar on the nanometer scale and highlights the possibility of coherent control of acoustic phonons at the atomic scale.

Link to the article

• ¹University of Stuttgart, Institute for Functional Matter and Quantum Technologies, 70569 Stuttgart, Germany
• ²Max Planck Institute for Solid State Research, 70569 Stuttgart, Germany
• ³University of Stuttgart, 4th Physics Institute and Research Center SCoPE, 70569 Stuttgart, Germany