Materials Science Research Lecture
***Refreshments at 3:45pm in Noyes lobby
Abstract:
In this talk I will give a common-sense introduction to the topic of strange metals. First observed in copper oxide high-temperature superconductors, the strange metal state is now found in a wide variety of materials, ranging from organic molecular crystals to cold atom simulators to twisted bilayer graphene. The key feature is Planckian dissipation, where the scattering rate is determined only by fundamental constants, representing a conjectured universal limit on the degree of quantum entanglement possible in a many-body system. I will trace the history of this field, from the marginal Fermi liquid theory of the late 1980's to the development of the SYK model by Sachdev and Ye in 1993, which Kitaev showed in 2014 could be "derived" using holographic duality, drawing intriguing parallels to black holes.
Additionally, I will present new momentum-resolved inelastic electron scattering experiments on density fluctuations in the strange metal Bi2Sr2CaCu2O8+x, revealing that the density fluctuations are quantum critical and exhibit conformal invariance—a property that featured prominently in Kitaev's derivation. Finally, I will discuss evidence for a newly identified excitation, the "scramblon," which is a characteristic of the extreme dissipative nature of these weird materials.
More about the Speaker:
Peter Abbamonte received his Ph.D. in Physics from the University of Illinois at Urbana-Champaign in 1999, having done his research with Eric Isaacs and Phil Platzman in the Materials Physics Department at Bell Laboratories. He then went to the University of Groningen in The Netherlands on an International Research Fellowship from the National Science Foundation to work with George Sawatzky, and returned to the U.S. as a postdoc in biophysics in Sol Gruner's group at Cornell University, where he studied photosynthesis in rhodobacter sphaeroides. He joined the scientific staff at Brookhaven National Laboratory in 2003, and was recruited to the University of Illinois in 2005, where he is currently the Fox Family Professor of Engineering in the Department of Physics and an affiliate of the Seitz Materials Research Laboratory.
Professor Abbamonte is one of the originators of the technique of resonant soft x-ray scattering with which he discovered the existence of a Wigner crystal in doped, quasi-1D spin ladders, and showed that stripes in copper-oxide superconductors are charged (among other achievements). This technique is now in use at every major synchrotron facility in the world. He is also known for his solution to the phase problem for inelastic x-ray scattering, which allows real-time imaging of electron motion in with attosecond time resolution. He has used this approach, for example, to image the formation of excitons in insulators, and to measure the effective fine structure constant of graphene.
Since 2011 Abbamonte has been focused on what he believes will be viewed as his crowning achievement: the development of a fully momentum-resolved, inelastic electron scattering (M-EELS) instrument that achieves an energy resolution of ~ 1 meV. This instrument is the only one in the world capable of studying the dynamic charge susceptibility, chi(q,omega), with full momentum resolution, and has already led to several major discoveries most notably the existence of a Bose condensate of excitons in TiSe2—widely covered in the popular press as the "discovery of excitonium" (see https://www.youtube.com/watch?v=17Kvxe6v5Ms ).
Abbamonte is the founder of Inprentus ( www.inprentus.com ), a premium manufacturer of XUV diffraction gratings. Inprentus was founded in 2012 at EnterpriseWorks, the startup incubator in the University of Illinois Research Park, and relocated to a dedicated facility in 2017. Inprentus has received Phase II SBIR funding from the NSF as well as significant Venture Capital investment, and has delivered high-resolution diffraction gratings to clients across the U.S., Europe, and Asia.