From multiferroics to cosmology Sang-Wook Cheong, Rutgers University New Brunswick, DMR 1104484

1. From multiferroics to cosmology Sang-Wook Cheong, Rutgers University New Brunswick, DMR 1104484 We have discovered that ferroelectric-trimerization domains in hexagonal REMnO3 (RE=rare earths) can have three different forms: stripes, loops and vortices. Even though the ferroelectric-trimerization transition is not Kosterlitz-Thouless-type, the formation of vortex domains resembles closely what happens in the Kosterlitz-Thouless transition due to associated slow dynamics. We found that the way that the vortex-antivortex distance increases with decreasing cooling rate across the transition is consistent with the so-called Kibble-Zurek mechanism, which is introduced to explain the non-equilibrium process of the trapped topological defects in the early universe before any matter was born. S. C. Chae, - - - S.-W. Cheong, PRL 108, 167603 (2012). W. Wu, - - - S.-W. Cheong, PRL 108, 077203 (2012). Fig. 1, The evolution of vortex-antivortex domain patterns with varying cooling rate. D  tn with n=0.23, where D is the average distance between a vortex and neighboring antivortices and n is inverse cooling rate.

2. From multiferroics to cosmology Sang-Wook Cheong, Rutgers University New Brunswick, DMR 1104484 Novel ground states in strong spin-orbit coupled IrTe2. IrTe2 undergoes a unique charge/orbital density wave transition below 260 K. We have discovered that Pd intercalation and also doping into IrTe2 induces superconductivity below 3 K. The above figure shows the phase diagram of T vs Pd concentration. The role of expected giant spin-orbit coupling in the compound needs to be further explored. J. Yang, - - - S.-W. Cheong, PRL 108, 116402 (2012). Liane Tarneki (a high-school student, through Partners in science program, organized by Liberty Science Center), Steve Carr (a volunteer high-school student) and Joe Matheussen (an undergraduate student, Physics. Rutgers), working in the PI’s lab in the 2011 summer.