Unbiased description of magnetic polarons in a Mott insulator

Polarons are among the most elementary quasiparticles of interacting quantum matter, consisting of a charge carrier dressed by an excited background. In Mott insulators, they take the form of a dopant surrounded by a distorted spin-background. Despite the fundamental importance of polarons for the electronic structure of strongly correlated systems, access to their internal structure was only recently realized in experiments, while controllable theoretical results are still lacking due to the sign problem. Here we report unbiased high-precision data obtained from worm-algorithm Monte Carlo that reveal the real-space structure of a polaron in the t-J model deep inside the region where the sign problem becomes significant. These results are directly comparable to recent quantum gas microscopy experiments, but give access to significantly lower temperatures.

Фотоиндуцированный магнитооптический эффект Керра в сульфиде европия EuS

The photoinduced magnetization in europium sulfide EuS was studied by the magneto-optical Kerr effect. It is experimentally established that when a sample is exposed to light with a photon energy greater than the band gap, photoinduced magnetization arises, associated with the formation of magnetic polarons with a large magnetic moment of about 3000 μB. The polarons are excited in a narrow temperature range of 12-18 K and form a superparamagnetic ensemble with an average polaron lifetime of 13 µs. An experimental setup for measuring photoinduced magnetization with the optical pump-and-probe method is described.