Seminarium "Modeling of Complex Systems"

In particle physics, a magnetic monopole remains a hypothetical elementary particle that has never been observed. However, certain condensed matter systems can contain effective magnetic monopoles. One of such systems are Artificial Spin Ices (ASIs) arrays of interacting nanomagnets that have allowed the design of geometrically frustrated exotic collective states not found in natural magnets. A key emergent description of fundamental excitations in ASIs is that of mobile quasiparticles that carry an effective magnetic charge  that is magnetic monopoles. These charge excitations can interact with each other and with applied magnetic fields via the magnetic analog ofthe electronic Coulomb interaction, representing the emergence of a range of novel phenomena, including the possibility of "magnetricity" – magnetic analog of electricity. While the presence of monopoles in ASI has been observed in pioneering imaging measurements, dynamical studies ofmonopole kinetics, and (especially) the ability to tune continuously through monopole-rich regimes in thermal equilibrium, remain at an early stage.In the seminar I will present a noise-based experimental approach that we have developed to passively "listen" to spontaneous magnetization fluctuations in archetypal, thermally active square ASI. The experiment, supported by standard Glauber Monte-Carlo simulations, reveals specificregions in the magnetic field-dependent phase diagram where the density of mobile monopoles increases well over an order of magnitude compared with neighboring regimes. Moreover, detailed noise spectra demonstrate that monopole kinetics are minimally correlated (i.e., most diffusive) inthis plasma-like regime. Experiments and Monte-Carlo simulations of more complex ASIs (including quadrupolar and vertex-frustrated Shakti and Tetris lattices) show similarly fascinating behavior, revealing surprisingly rich field-dependent phase diagrams of these systems. The discovery of on-demand monopole regimes with tunable kinetic properties opens the door tonew probes of magnetic charge dynamics and provides a new paradigm for the studies of magnetricity in artificial magnetic materials.

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The seminar will be held in hybrid mode: in room 1.40 (IPC PAS).During the seminar the coffee and cakes are provided. Join Zoom Meetinghttps://uw-edu-pl.zoom.us/j/96378632993?pwd=MVgdPR80oKaE4pjLufb2NCtg6ql4Ax.1Meeting ID: 963 7863 2993Passcode: 569551