Strain Engineering of a Charge Density Wave in a Transition Metal Dichalcogenide 2H-NbSe2

Transition metal dichalcogenides host a range of fascinating optoelectronic properties. One of the prominent members of this family is the superconducting 2H-NbSe₂ (Tc~7.2 K), which also hosts a charge density wave (CDW) phase (Tc~33 K) that has been intensely studied for decades. External perturbations, such as strain or pressure, can in principle push a CDW phase into a different ordering geometry. However, engineering this type of quantum criticality has been experimentally challenging. Here, we apply a new method in combination with STM/STS to deform and study the surface of 2H-NbSe₂. We discuss the intriguing observation of two new CDW phases, which we can directly attribute to local strain. We combine our STS measurements of the electronic band structure with theoretical calculations to discover distinct roles of electrons and phonons in the formation of different phases. Our work establishes a new platform for the explorations of strain induced quantum phase transitions in this and other related materials.