Emergent States of Complex Quantum Matter: Past Present and Future
- J.C. Seamus Davis, Cornell University & Brookhaven National Laboratory (BNL)
Thursday, April 4, 4:10 PM - Physics and Astronomy Colloquium
Biomedical & Physical Sciences Bldg., Rm. 1415
For more than a century, emergent states of quantum matter such as superconductors, superfluids and supergasses have played a central role in condensed matter and macroscopic quantum physics. We will begin with a review of the history of these discoveries and also some of the their profound impacts on other fields such as elementary particles, astrophysics and cosmology.
Today, high-Tc superconductivity (HTS) is once again at the epicentre of quantum matter research. This is because of the extraordinary discovery of iron-based HTS in 2008. While only copper-based HTS was known, the hypothesis that the single-orbital strong correlations of its Mott-insulator state contain the key to the superconductivity was persuasive. However, the iron-based superconductors are dominated by multi-orbital Hund’s rule magnetism and are without correlated insulator phases. This unexpected contrast has renewed focus on identifying the true essence of HTS. Here I will outline our efforts, by direct visualization of electronic structure at the atomic scale, to compare and contrast the phenomenology of the copper-based and iron-based superconductors. We study the electronic structure of the ‘parent’ phases (Science 327, 181 (2010)); Science 333, 426 (2011)), the atomic-scale effects of the substitutional doping processes (Nature Physics 8, 534 (2012); arXiv:1211.8454 (2013)), and the distinct but similarly unconventional forms of superconductivity (Nature 454, 1072 (2008); Science 336, 563 (2012)) in search of a universal explanation for high-Tc superconductivity.
Finally, I hope to survey some of the impending challenges in emergent electronic matter research, touching on systems including Heavy Fermions, Quantum Critical Matter, Quantum Spin Liquids, Magnetic Monopole Liquids, Electronic Liquid Crystals and Topological Superfluids & Superconductors.