Strain-Induced Proliferation of Electronic Orders in Quasi-2D Superconductors (Part I)

Quantum materials often have rich phase diagrams which host numerous phases that coexist or compete with one another. Some quasi-2D materials such as 2H-NbSe2 host both superconducting and multiple charge-ordered phases. Applied uniaxial strain is a powerful tool for perturbing systems to study how various electronic orders are suppressed or enhanced.

In the first part of this talk, we perform scanning tunneling microscopy/spectroscopy (STM/STS) measurements on 2H-NbSe2. We observe a variety of novel charge density wave (CDW) phases not found in the unstrained system. Large area topography measurements reveal a transition between a coherent, long range (4 x 1) CDW stripe crystal to a disordered, liquid crystal-like short range order. Detailed STM measurements reveal that this spatial transition originates from the presence of a strain gradient. Our results highlight the important role of residual strain in establishing long-range stripe order in CDWs.