Abstract:
In contrast to the band theory at the heart of the semiconductor revolution, where electrons can be treated individually despite their density, many exotic properties of today’s forefront materials stem from strong electronic interactions, that preclude single particle interpretation. Cuprates are a paradigmatic example, where strong interactions give rise to an array of exotic states and broken symmetries, including high-temperature superconductivity.  It has been proposed that that this complex phase diagram is controlled by a quantum phase transition in the midst of superconductivity. To address the nature of the governing electronic interactions, we use atomically-resolved scanning tunneling spectroscopy to image an electronic density wave across the critical doping.  We discover a reorganization of the electronic structure that abruptly shifts the density wave mechanism from strong to weak coupling physics. Furthermore, while the change of the underlying physics is sudden, the wavelength of the density wave evolves smoothly. This last observation points to a new paradigm to understand the quantum phase transition and the import of strong interactions in the cuprates.

Host: The MIT Society of Physics Students
 
Refreshments at 3:30pm in 4-349 (Pappalardo Community Room)

View the entire physics colloquia schedule at http://web.mit.edu/physics/events/colloquia.html