报告题目：Density Wave Probes the Quantum Phase Transition in a Cuprate Superconductor

报 告 人：Jennifer E Hoffman，Harvard University

报告时间：2018-08-24 15:00

报告地点：理科楼郑裕彤讲堂

报告摘要：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)2CuO6+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.