Critical opalescence across the doping driven Mott transition in optical lattices of ultracold atoms. / Walsh, Caitlin; Semon, P.; Sordi, Giovanni; Tremblay, A. -M. S.

In: Physical Review B, Vol. 99, No. 16, 165151, 30.04.2019, p. 1-9.

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### Abstract

Phase transitions and their associated crossovers are imprinted in the behavior of fluctuations. Motivated by recent experiments on ultracold atoms in optical lattices, we compute the thermodynamic density fluctuations $\delta N^2$ of the two-dimensional fermionic Hubbard model with plaquette cellular dynamical mean-field theory. To understand the length scale of these fluctuations, we separate the local from the nonlocal contributions to $\delta N^2$. We determine the effects of particle statistics, interaction strength $U$, temperature $T$ and density $n$. At high temperature, our theoretical framework reproduces the experimental observations in the doping-driven crossover regime between metal and Mott insulator. At low temperature, there is an increase of thermodynamic density fluctuations, analog to critical opalescence, accompanied by a surprising reduction of the absolute value of their nonlocal contributions. This is a precursory sign of an underlying phase transition between a pseudogap phase and a metallic phase in doped Mott insulators, which should play an important role in the cuprate high-temperature superconductors. Predictions for ultracold atom experiments are made.
Original language English 165151 1-9 9 Physical Review B 99 16 https://doi.org/10.1103/PhysRevB.99.165151 Published - 30 Apr 2019
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