Hart Goldman- University of Chicago

Title: Composite fermions and the zero-field fractional quantum Hall effect

Abstract: 

Among the greatest discoveries of 20th century physics was the fractional quantum Hall (FQH) effect in two dimensional semiconductor materials immersed in a strong magnetic field. Since their initial experimental observation, FQH phases have been understood to be quintessential topological phases of matter, exhibiting long ranged quantum entanglement and playing host to exotic, emergent excitations with electric charge and exchange statistics that are fractions of those of the electron.

Remarkable recent experiments have revealed evidence of the FQH effect in systems without any external magnetic field, in a growing number of two dimensional  materials. In this colloquium, I will present a unified theoretical framework for understanding the emergence of zero-field FQH phases in terms of “composite fermions,” emergent particles that are combinations of electric charge and magnetic vortices. One central prediction of the composite fermion picture is the possibility of an  “anomalous composite Fermi liquid” (ACFL) phase, which is a strongly interacting metal of composite fermions. I will describe theoretical and numerical evidence for this ACFL state, as well as its importance in the zero-field FQH phase diagram. I will also present the experimental implications of the ACFL and discuss the growing evidence for this phase in zero-field FQH materials. I will conclude by describing how these ideas can launch us into addressing the exciting new questions and research directions in this emerging field.

Bio: Hart Goldman completed his PhD in 2020 at the University of Illinois at Urbana-Champaign, where he worked on a wide range of topics in the study of two dimensional quantum materials with strong interactions and long-ranged entanglement under the supervision of Eduardo Fradkin. After his PhD, Hart continued this line of work as a Gordon and Betty Moore Postdoctoral Fellow at MIT.  In 2023, Hart became a Kadanoff Fellow at the University of Chicago