Abstract
Polaritonic lattices offer a unique testbed for studying nonlinear driven-dissipative physics. They show qualitative changes of their steady state as a function of system parameters, which resemble non-equilibrium phase transitions. Unlike their equilibrium counterparts, these transitions cannot be characterised by conventional statistical physics methods. Here, we study a lattice of square-arranged polariton condensates with nearest-neighbour coupling, and simulate the polarisation (pseudospin) dynamics of the polariton lattice, observing regions with distinct steady-state polarisation patterns. We classify these patterns using machine learning methods and determine the boundaries separating different regions. First, we use unsupervised data mining techniques to sketch the boundaries of phase transitions. We then apply learning by confusion, a neural network-based method for learning labels in a dataset, and extract the polaritonic phase diagram. Our work takes a step towards AI-enabled studies of polaritonic systems.
Highlights
Polaritonic lattices offer a unique testbed for studying nonlinear driven-dissipative physics
We have studied polarisation patterns that emerge as steady states in nonlinear polaritonic lattices
For different values of pump gain and lattice tunnelling rates, we see qualitatively distinct patterns that correspond to polariton phases with mixtures of ferromagnetic and antiferromagnetic bonding of chequerboard, stripe, diagonal and cluster types
Summary
Polaritonic lattices offer a unique testbed for studying nonlinear driven-dissipative physics. Many fundamental features in nature such as the complicated patterns appearing on animal coats[36] and proliferation of defects in the Higgs field[37] are linked to non-equilibrium analogues of phase transitions This question was investigated in optical systems, noting cooperative phenomena and self-organisation during lasing[38,39,40]. Perhaps the most exciting advancement are lattices of polariton condensates which have emerged as a promising way to create extended systems of trapped nonlinear light[53] They can be realised using a variety of techniques such as lithographically patterned inorganic[54] and organic[55] cavities which act on the photonic mode, or using sculpted nonresonant lasers which act on the exciton mode[56]. With rapid improvements in the abovementioned techniques, the coherence length of polariton condensate lattices greatly exceeds the typical unit cell size[58,61,74] which gives hope to study new and interesting phases of dissipative bosonic matter determined by the coherent flow of polaritons across the lattice sites
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