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Einladung zum Physikalischen Kolloquium 2015/2016

Quantum spin liquids and Majorana metals

One of the most intriguing phenomena in strongly correlated systems is the fractionalization of quantum numbers — familiar examples include the spin-charge separation in one-dimensional metallic systems, the fractionalization of the electron in fractional quantum Hall states or the emergence of monopoles in spin ice.

This talks aims to elucidate this concept, as well as the rich behavior in its wake. In particular, I will focus on the fractionalization of magnetic moments in a certain class of Mott insulators, which might be realized in a class of recently synthesized Iridate compounds. Such systems are among the prime examples for quantum spin liquids — strongly correlated spin systems that show no magnetic order down to zero temperatures and whose spin excitations are fractionalized. In the models we focus on, the fractionalized degrees of freedom are Majorana fermions that — just as usual fermions — may form various types of (semi-)metals. Such systems can mimic the rich behavior found in Dirac materials, albeit with spin instead of electronic degrees of freedom.