Center for Artificial Low Dimensional Electronic Systems

“Phase-resolved Non-Linear THz-Spectroscopy revealing the Higgs response in superconducting cuprates ”

Dr. Stefan Kaiser

October 22(Tue) - October 22(Tue), 2019

14:00

Seminar Room #512, Hogil Kim Memoral Bldg.

The complex phase diagram of cuprate high-Tc superconductor is due to an intriguing interplay of different orders such as the pseudogap, or charge order. Despite intensive spectroscopic measurements of these ordered states, yet the microscopic mechanism behind high-Tc superconductivity is still lacking. In particular the collective dynamics of the superconducting order parameter, the Higgs mode, was not accessible so far. Here we report on "Higgs spectroscopy" in cuprate superconductors that we accomplished by using a high-field multicycle THz pulse, which nonlinearly couples to the superconducting condensate and leads to characteristic third harmonic generation. We identify the driven Higgs amplitude response of the superconducting order parameter in three archetypal families of cuprate thin films and we report on a novel collective mode universally exhibited by optimally doped samples. In addition, we find a finite Higgs-like response above Tc that might be interpreted as finite pairing amplitude even above Tc. Within the tutorial we will introduce the technology behind generating high field THz lights pulses and their application in driving collective dynamics in superconductors. In particular we will emphasise that analysing the amplitude and phase response of the non-linear driven system reveals novel and unprecedented insight into the dynamics of superconductors.