The research conducted by a team comprising members from Skoltech, Universitat Politècnica de València, Institute of Spectroscopy of RAS, University of Warsaw, and University of Iceland has shed light on the spontaneous formation and synchronization of multiple quantum vortices in optically excited semiconductor microcavities. These polariton quantum vortices, formed in adjacent cells of optically generated lattices, were observed to exhibit an interesting phenomenon known as “antiferromagnetic coupling,” where the vortices have opposite topological vortex charges.
The structured artificial lattices consisting of coupled polariton vortices present a promising avenue for the study and simulation of condensed matter systems. By leveraging the orbital angular momentum of polariton condensates as a replacement for spin angular momentum, researchers aim to explore the dynamics of quantum vortices in exciton-polariton systems in a novel manner. While previous studies have focused on the behavior of quantum vortices in such systems with various optical excitation techniques, the demonstration of extended two-dimensional lattices of phase-locked quantum vortices has been lacking until now.
The experiments were conducted at Skoltech’s Photonics Center’s Hybrid Photonics Laboratory under the leadership of Professor Pavlos Lagoudakis. The researchers utilized a semiconductor planar microcavity, composed of two highly reflective mirrors with InGaAs quantum wells in between. This configuration, operating in the strong-light matter coupling regime, led to the formation of exciton–polaritons or microcavity polaritons, which are composite states of excitons in quantum wells and confined cavity photons.
Skoltech Assistant Professor Sergey Alyatkin, the first author of the paper, described the optical excitation process, which involved utilizing a patterned laser beam generated using spatial light modulation techniques. By adjusting the lattice parameters and excitation power, the team was able to induce polaritons condensation within the lattice cells. Interestingly, the study revealed that while individual lattice cells showed tendencies towards both vortex and antivortex states, neighboring cells interacted to form stable solutions with opposite topological charges.
Dr. Helgi Sigurðsson from the University of Warsaw provided theoretical insights into the observed phenomenon, suggesting the presence of extended antiferromagnetic order within the triangular lattice of vortices. By examining the vortex charge distribution across multiple lattice cells and correlating them with the Ising spin Hamiltonian configurations, the researchers were able to establish a link between the orbital angular momentum of the condensates and the antiferromagnetic spin behavior.
The extensive statistical analysis of the experimental data posed a significant challenge for the researchers, requiring them to delve deep into the intricate details of the vortex lattice formation and synchronization. The findings of this study open up new avenues for exploring the behavior of quantum vortices in driven-dissipative systems and pave the way for further investigations into the complex interactions within artificial lattices of polariton vortices.
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