Interesting phenomena in quantum materials are often found near boundaries between different competing ground states.

Understanding the competition between these states is a central problem in condensed matter physics because of the potential applications to quantum computing and superconductivity.

There are many different types of ground states but the one that’s important here is a charge density wave (CDW). This is where the electron density of a material becomes modulated in a periodic pattern.

TbTe₃, or terbium tritelluride is a quasi-two-dimensional material made up of alternating layers of conducting tellurium (Te) planes and insulating rare-earth terbium (Tb) block layers.

It has attracted a lot of interest recently though because it has two competing CDW states and represents an excellent platform to study new quantum phenomena.

Previous experiments have shown that these states can be tuned when the material is put under pressure, even leading to an induced superconducting state.

These experiments all used an isotropic pressure – the same in all directions. However, because this material is quasi-two dimensional, it would be even more interesting to see how it responds to a strain in one particular direction.

This is exactly what the team at SLAC have done.

They used ultrafast optical reflectivity to probe the dynamics of the competing CDW states in TbTe₃ at different strains.

They found that these two competing states are incredibly similar in energy and become more stable with increasing strain.

What’s really exciting though is the method they used. Their measurements were recorded in a pump-probe setup on timescales of a couple of picoseconds (trillionths of a second).

Combined with the application of a directional strain, this technique could be used in the future to study many other quantum materials with exciting properties.