Konstantin Tiurev

Observation of isolated monopoles in a quantum field

Making a monopole in an atomic gas Some “grand unified theories” of physics predict the existence of the so-called magnetic monopole. No such particles have been seen, but analogs of monopoles may be observable in quantum fluids. Ray et al. created such an analog in a gas of ultracold 87Rb atoms with three spin states at their disposal. The authors used a protocol involving external magnetic fields with particular spatial distributions to create and observe a monopole-like spin texture in the gas. Science, this issue p. 544 An analog of the magnetic monopole has been created and observed in an ultracold gas of rubidium-87 atoms. Topological defects play important roles throughout nature, appearing in contexts as diverse as cosmology, particle physics, superfluidity, liquid crystals, and metallurgy. Point defects can arise naturally as magnetic monopoles resulting from symmetry breaking in grand unified theories. We devised an experiment to create and detect quantum mechanical analogs of such monopoles in a spin-1 Bose-Einstein condensate. The defects, which were stable on the time scale of our experiments, were identified from spin-resolved images of the condensate density profile that exhibit a characteristic dependence on the choice of quantization axis. Our observations lay the foundation for experimental studies of the dynamics and stability of topological point defects in quantum systems.

Experimental Realization of a Dirac Monopole through the Decay of an Isolated Monopole

Magnetic monopoles have been sought for decades but never definitively observed. Recent experiments have created different analogs of monopoles in Bose-Einstein condensates, including quantum-mechanical and Dirac monopoles. Now a new experiment in this system shows how a quantum-mechanical monopole can evolve into a Dirac monopole.

Three-dimensional skyrmions in spin-2 Bose-Einstein condensates

We introduce topologically stable three-dimensional skyrmions in the cyclic and biaxial nematic phases of a spin-2 Bose-Einstein condensate. These skyrmions exhibit exceptionally high mapping degrees resulting from the versatile symmetries of the corresponding order parameters. We show how these structures can be created in existing experimental setups and study their temporal evolution and lifetime by numerically solving the three-dimensional Gross-Pitaevskii equations for realistic parameter values. Although the skyrmions are eventually destroyed due to the instability of the underlying magnetic phase, their lifetimes are found to be long enough for experimental detection.

Decay of an isolated monopole into a Dirac monopole configuration

We study numerically the detailed structure and decay dynamics of isolated monopoles in conditions similar to those of their recent experimental discovery. We find that the core of a monopole in the polar phase of a spin-1 Bose–Einstein condensate contains a small half-quantum vortex ring. Well after the creation of the the monopole, we observe a dynamical quantum phase transition that destroys the polar phase. Strikingly, the emergent ferromagnetic order parameter exhibits a Dirac monopole in its synthetic magnetic field.

Evolution of an isolated monopole in a spin-1 Bose-Einstein condensate

The evolution of an isolated monopole is investigated in a ferromagnetically coupled, spin-1 Bose-Einstein condensate in the absence of external magnetic fields. It is predicted that a polar-core spin vortex may emerge spontaneously in the resulting ferromagnetic order-parameter field.

Monopoles in Spinor Bose-Einstein Condensates

We describe the creation and observation of Dirac monopoles in a synthetic magnetic field, and also provide evidence of isolated topological point defects in the order parameter of a spinor Bose-Einstein condensate.