Q-MAC meetings in 2019:

Regular meetings of the Q-MAC team

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Dieter Jaksch awarded with the 2018 Thomas Young Medal and Prize

for "his contributions to theoretical proposals enabling the study of non-equilibrium quantum many-body dynamics with unprecedented microscopic control in ultra-cold atoms, and establishing them as a quantum technologies platform".

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Publication Detail / Abstract

J. Ruppen, J. Teyssier, I. Ardizzone. O. E. Peil, S. Catalano, M. Gibert, J. M. Triscone, A. Georges, D. van der Marel

Impact of antiferromagnetism on the optical properties of rare earth nickelates

published in Physical Review B on July 17, 2017
> Full text via publisher
We study the temperature dependence of the optical conductivity of rare-earth nickelate films of varying composition and strain close to the antiferromagnetic ordering temperature, TN. Two prominent peaks at 0.6 and 1.3 eV, which are characteristic of the insulating phase, display a small but significant increase in intensity when the material passes from para- to antiferromagnetic. This observation indicates the presence of a positive feedback between antiferromagnetic (AF) and bond disproportionation (BD) order. By analyzing the temperature dependence near TN, and using a Landau-type free-energy expression for BD and AF order, we infer that BD order is a necessary condition for the AF phase to appear, and that the antiferromagnetism contributes to stabilization of the bond disproportionation. This model also explains why hysteresis is particularly strong when the transition into the insulating state occurs simultaneously with antiferromagnetic order.
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