Physics Colloquium
Visualizing Electron-Pair Fluids and Crystals at the Atomic Scale
Dr. Xiaolong Liu
Kavli Fellow, Physics
Cornell University
Pairing of electrons with opposite momenta takes place inside most conventional superconductors, leading to translationally invariant fluids of electron pairs. Meanwhile, electron pairs can form crystals known as pair density waves (PDWs) that break translational symmetry. Experimental evidence of PDWs, however, remains scarce due to the difficulty in imaging the superconducting condensate. In this talk, I will first introduce our recent discovery of a PDW state in a transition metal dichalcogenide, NbSe 2 , using atomic-resolution scanned Josephson-tunneling microscopy (SJTM). We observe two characteristic signatures of PDWs including periodic modulations of electron-pair density and superconducting energy gap at the wavevectors of preexisting charge density waves. Using the same SJTM technique, I will then discuss our capability in visualizing the velocity field and supercurrent density of electron-pair fluid flow around quantum vortices. Finally, I will share my perspective on applications of such novel techniques in other emerging quantum materials.
Hosted by Prof. Janko
All interested persons are invited to attend remotely—email physics@nd.edu for information.