This special Physics department colloquium is scheduled for Tuesday 5/5/15 at 4:00 pm in Room 135. Coffee, tea and cookies are served at 3:45 pm in the same room. Anyone is welcome.

Broken Time-Reversal in High-Tc Superconductors
Manoj Kumar Kashyap, PhD Candidate/UWM Dept. of Physics

A century after the discovery of superconductivity at the lab of Kamerlingh Onnes in 1911, it is noticeable that the phenomenon is quite ubiquitous in nature. In addition to a long list of superconducting alloys and compounds, almost half the elements in the periodic table superconduct. By the late seventies, superconductivity was thought to be well understood. This turned out to be a myth, with the discovery of unconventional superconductors that defied Bardeen-Cooper-Schrieffer (BCS) theory. Cuprates have been the most prominent example since their discovery in 1986 by Bednorz and Müller. This discovery was followed by yttrium barium copper oxide (YBCO) in 1987, commencing the era of high temperature superconductivity. The astonishingly rich phase diagram of cuprates includes the pseugap phase which was earlier thought to be a precursor to superconductivity. Now signatures of broken symmetries have been seen, indicating a true phase transition. Is it possible to describe all these broken symmetries within a single theory? Here I describe a translational invariant magnetoelectric (ME) loop current order parameter which naturally arises out of pair density wave (PDW) order as an explanation for the pseudogap phase.