Physics Club Colloquium
Yu He, Yale University, “Breaking a metal via low dimensional fluctuations”
February 28, 2022 at 4:00PM via Zoom
Zoom link: https://yale.zoom.us/j/93877032663?pwd=UnYram1TS1VXUjNIdFpFTHZTRDVWdz09 (passcode: 863491)
Professor Yu He, Yale University
Yu He joined Yale Applied Physics as an assistant professor in the fall of 2020. His research mainly utilizes light-matter interaction to investigate correlated electronic systems and other functional quantum materials. He focuses on dissecting novel materials’ microscopic degrees of freedom - electronic, lattice and spin - via angle-resolved photoemission spectroscopy and x-ray scattering techniques, in order to glean mechanistic insights to better engineer material properties. Yu obtained his B.S. in Physics from University of Science and Technology of China (USTC), M.S. in Electrical Engineering and Ph.D. in Applied Physics from Stanford University. Prior to arriving at Yale, he worked as a Miller Research Fellow at the University of California at Berkeley.
Breaking a metal via low dimensional fluctuations
Metals (bronze & iron) used to define eras in human history. Then came the age of semiconductors (silicon), and now superconductors (qubits!). Transitions between these states of matter have taken the center stage of solid state research since the dawn of quantum mechanics. Most metal-to-insulator and metal-to-superconductor transitions are so dramatic that some symmetries need to be broken in the material. But it need not be so, especially in low dimensions.
With the help of momentum-resolved spectroscopies, we show that superconducting and phonon fluctuations in low dimensional materials are massively enhanced, which readily change the electron behaviors in a metal. These wild fluctuations at low dimensions make metals highly sensitive to external tuning without needing to break any global symmetry. As the experimental incarnation of correlation functions, fluctuations can carry much more information than the corresponding symmetry-broken phases. I will also discuss how to exploit the rich information encoded in these fluctuating states via ever-improving photoemission spectroscopy and data mining methods.
[1] Phys. Rev. X 11, 031068 (2021)
[2] DOI: 10.21203/rs.3.rs-1066131/v1 (preprint)
[3] Rev. Mod. Phys. 93, 025006 (2021)