The strong electronic correlations of the doped antiferromagnetic Mott insulator give rise to unconventional phases beyond high temperature superconductivity in the cuprates.  Multiple broken symmetries have been reported, though a complete description of their emergence and interaction is missing. At the heart of this complex phase diagram is evidence of a quantum critical point, where disconnected Fermi arcs jump inexplicably to a large Fermi surface as holes are added. Here, we use sub-unit-cell scanning tunneling microscopy and spectroscopy (STM/S) to track the d-form factor density wave throughout the phase diagram as a local fingerprint of the dominant interactions in (Bi,Pb)₂(Sr,La)₂CuO_6+d. Crucially, we use nanoscale electronic inhomogeneity as a tool to access a range of dopings within a single sample. We discover an abrupt change in the evolution of the modulation wavevector, signaling a commensurate to incommensurate transition that is coincident with the Fermi surface transition.  Furthermore, the rapid growth of the wavelength on the overdoped side of the transition is at odds with a simple Fermi surface instability, providing evidence for persistent effects of strong correlations.

 

Bio: Professor Jennifer E Hoffman received her B.S. degree from Harvard University in 1999, PhD from University of California, Berkeley in 2003. She then went to Stanford University for postdoctoral research.  After staying there for one year, she joined Harvard University as assistant scientist in 2004, and became the tenured professor in 2015. Professor Hoffman is interested in how electrons behave within exotic materials, and has contributed to the observations of checkerboard and quasiparticle interference in cuprates. She has been named a 2008 NSF Career Fellow, a 2010 Sloan Research Fellow, a 2013 Radcliffe Fellow, and a 2014 Moore Foundation Experimental Investigator. Her current interest is in the physics of high temperature superconductors, topological insulators, and strongly correlated systems.