Dissociation dynamics of singly charged vortices into half-quantum vortex pairs

Abstract

The quest for identification and understanding of fractional vorticity is a major subject of research in the quantum fluids domain, ranging from superconductors, superfluid Helium-3 to cold atoms. In a two-dimensional Bose degenerate gas with a spin degree of freedom, the fundamental topological excitations are fractional vortical entities, called half-quantum vortices. Convincing evidence for the existence of half-quantum vortices was recently provided in spinor polariton condensates. The half-quantum vortices can be regarded as the fundamental structural components of singly charged vortices but, so far, no experimental evidence of this relation has been provided. Here we report on the direct and time-resolved observation of the dynamical process of the dissociation of a singly charged vortex into its primary components, a pair of half-quantum vortices. The physical origin of the observed phenomenology is found in a spatially inhomogeneous static potential that couples the two spin components of the condensate.

Incoherent excitation and switching of spin states in exciton-polariton condensates

“…8 (d), (h)], they are maintained and stabilised by internal Josephson current between the spin components and do not exist in the absence of linear coupling (J = 0). We note that no phase singularities appear in the linearly-polarized basis, which sets these structures apart from the previously described half-charge vortices [29][30][31] VI. CONCLUSIONS…”

Half-Quantum Vortices in an Antiferromagnetic Spinor Bose-Einstein Condensate

“…In the absence of long-range order in two dimensions [3], the superfluid phase transition in 2D is associated with vortex-antivortex pairing as described by the Berezinskii-Kosterlitz-Thouless (BKT) theory [4,5]. Hence fractional quantum vortices, introduced as new point defects, represent an interesting opportunity to explore for exotic superfluid phases, possibly beyond the BKT physics.Quantum vortices having h/2m circulation, so-called half-quantum vortices (HQVs) have been experimentally observed in spinor superfluid systems such as excitonpolariton condensates [6][7][8] and triplet superconductors [9]. In previous cold atom experiments, HQV states were created with an optical method in two-component Bose-Einstein condensates (BECs) [10], where the two components are not symmetric in terms of interactions.…”

Spin-Orbit Coupling for Photons and Polaritons in Microstructures

“…In combination with the strong spin-dependent interactions naturally present in microcavity-polariton devices and the possibility of scaling up to lattices of arbitrary geometry [16][17][18], the realization of such a coupling in semiconductor microcavities would open the way to the simulation of many-body effects in a new quantum optical context [19]. Some examples would be the controlled nucleation of fractional topological excitations [20,21], the formation of polarization patterns [22,23], the simulation of spin models using photons [24], topological insulation [25,26], or the generation of fractional quantum Hall states for light [27,28].…”