# Light-Induced Charge Density Wave in LaTe$_3$

## TL;DR

This study demonstrates that ultrafast light excitation can induce a transient, non-equilibrium charge density wave in LaTe$_3$, revealing competition between different CDW states and opening pathways to access novel phases beyond equilibrium.

## Contribution

The paper presents the first observation of light-induced competition and switching between unidirectional charge density waves in LaTe$_3$, a phenomenon not seen in equilibrium conditions.

## Key findings

- Photoexcitation weakens the original CDW along c-axis.
- A new CDW along the a-axis emerges transiently.
- Timescales for CDW suppression and emergence are nearly identical.

## Abstract

When electrons in a solid are excited with light, they can alter the free energy landscape and access phases of matter that are beyond reach in thermal equilibrium. This accessibility becomes of vast importance in the presence of phase competition, when one state of matter is preferred over another by only a small energy scale that, in principle, is surmountable by light. Here, we study a layered compound, LaTe$_3$, where a small in-plane (a-c plane) lattice anisotropy results in a unidirectional charge density wave (CDW) along the c-axis. Using ultrafast electron diffraction, we find that after photoexcitation, the CDW along the c-axis is weakened and subsequently, a different competing CDW along the a-axis emerges. The timescales characterizing the relaxation of this new CDW and the reestablishment of the original CDW are nearly identical, which points towards a strong competition between the two orders. The new density wave represents a transient non-equilibrium phase of matter with no equilibrium counterpart, and this study thus provides a framework for unleashing similar states of matter that are "trapped" under equilibrium conditions.