Recent research conducted by a team of scientists 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. The fascinating findings of this study have been published in Science Advances and provide insights into the behavior of polariton quantum vortices in artificial lattices created through optical means.
The study revealed that the polariton quantum vortices formed in adjacent cells of optically generated lattices exhibit an intriguing phenomenon known as “antiferromagnetic coupling”. This implies that the vortices in these neighboring cells tend to have opposite topological vortex charges, creating a synchronized pattern within the lattice. By structuring artificial lattices composed of coupled polariton vortices, researchers have opened up new possibilities for investigating and simulating condensed matter systems utilizing the orbital angular momentum of the polariton condensate.
The experiments were conducted at Skoltech’s Photonics Center’s Hybrid Photonics Laboratory, under the leadership of Professor Pavlos Lagoudakis. The researchers employed a semiconductor planar microcavity, which consists of two highly reflective mirrors enclosing InGaAs quantum wells. This arrangement leads to the formation of exciton-polaritons or microcavity polaritons, which are quasiparticles arising from the coupling between excitons in quantum wells and confined cavity photons. By optically exciting the semiconductor microcavity sample using a patterned laser beam generated through spatial light modulation techniques, the researchers were able to observe the condensation of polaritons within the cells of the lattice.
In their experiments, the scientists discovered that in a single cell, the trapped condensate exhibited both vortex and antivortex states with similar probabilities. However, in neighboring cell pairs, the vortices interacted and formed stable solutions with opposite topological charges, resulting in vortex-antivortex or antivortex-vortex pairings. Further analysis was carried out on triangular structures containing multiple cells, as well as larger triangular lattices of vortices, to study the physics of the condensates.
The most intriguing observation made during the study was the indication of extended antiferromagnetic order within the triangular lattice of vortices. The researchers, including theoretician Dr. Helgi Sigurðsson from the University of Warsaw, noted that the vortex charge of each condensate across the lattice cells exhibited correlations with the low-energy configurations of the Ising spin Hamiltonian. This finding suggested that the observed orbital angular momentum in the stable solutions of the vortex lattice was significantly linked to the low-energy solutions of antiferromagnetically coupled Ising spins.
The research conducted on the spontaneous formation and synchronization of quantum vortices in semiconductor microcavities has provided valuable insights into the behavior of polariton quantum vortices in structured artificial lattices. The discovery of antiferromagnetic coupling and the correlations with Ising spin Hamiltonian configurations open up new avenues for studying complex condensed matter systems using exciton-polariton dynamics. The findings of this study have the potential to impact various fields of research ranging from quantum optics to condensed matter physics.