Researchers at the Indian Institute of Science (IISc), Bangalore, have developed a method to control phonon properties by adjusting twist angles between layers of two-dimensional (2D) materials. This breakthrough could pave the way for engineering materials vital for photonic, quantum and electronic applications.

Phonons are energy waves travelling through a crystal lattice when atoms vibrate, much like ripples forming in a pond. Their properties are crucial for developing optoelectronics and tunable photonic devices. Controlling these properties has been a major research focus.

The study, published in ACS Nano, demonstrates that varying twist angles between one degree and seven degrees in tungsten diselenide (WSe2) homobilayers can induce splitting in phonon modes. Raman spectroscopy revealed temperature-driven changes in phonon behaviour, particularly at temperatures below fifty Kelvin, highlighting complex electron-phonon interactions and phonon anharmonicity.

The findings show how moiré superstructures, formed when overlapping 2D lattices align at slight angles, influence both phononic and electronic properties. This work used the Raman spectroscopy facility established with support from the Fund for Improvement of Science and Technology Infrastructure (FIST) programme of the Department of Science and Technology (DST).

The research opens new possibilities for designing materials suited to emerging quantum technologies.

Source: Press Information Bureau Delhi