Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session S22: Artificial Spin Ice and Related Frustrated Artificial MaterialsInvited
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Sponsoring Units: DCMP GMAG Chair: Cristiano Nisoli, Los Alamos National Lab Room: New Orleans Theater A |
Thursday, March 16, 2017 11:15AM - 11:51AM |
S22.00001: Recent development of artificial spin ice: a theoretical perspective Invited Speaker: Gia-Wei Chern I will discuss recent development of artificial spin ice mainly from the theoretical viewpoint. Specifically, I will talk about the following topics: (1) Physics related to magnetic charge degrees of freedom. The charge-ordered phase of kagome spin ice. Magnetic charge screening in shakti, dice, and pentagonal spin ices. (2) Emergent frustration in shakti spin ice, and other new lattices with vertex frustration. (3) Emergent reduced dimensionality and sliding phase in tetris spin ice. (4) Athermal or relaxational dynamical phenomena of artificial spin ice; disorder; avalanches; return-point memory. (5) Micromagnetic simulations of artificial spin ice. Magnetization reversal. (6) Reconfigurable spin wave band structure in artificial spin ice and Magnonics. (6) Magneto-transport poperties of artificial spin ice. [Preview Abstract] |
Thursday, March 16, 2017 11:51AM - 12:27PM |
S22.00002: Engineering of frustration in colloidal artificial ices realized on microfeatured grooved lattices Invited Speaker: Pietro Tierno Artificial spin-ice systems, namely lattices of interacting single domain ferromagnetic islands, have been used to date as microscopic models of frustration induced by lattice topology, allowing for the direct visualization of spin arrangements and textures. However, the engineering of frustrated ice states in which individual spins can be manipulated in situ and the real-time observation of their collective dynamics remain both challenging tasks. Inspired by recent theoretical advances, we realize a colloidal version of an artificial spin ice system using interacting polarizable particles confined to lattices of bistable gravitational traps. We show quantitatively that ice-selection rules emerge in this frustrated soft matter system by tuning the strength of the pair-interactions between the microscopic units. Via independent control of particle positioning and dipolar coupling, we introduce monopole-like defects and strings and use loops with defined chirality as an elementary unit to store binary information. [Preview Abstract] |
Thursday, March 16, 2017 12:27PM - 1:03PM |
S22.00003: Dynamics of Bound Monopoles in Artificial Spin Ice: How to store energy in Dirac Strings. Invited Speaker: Elena Vedmedenko Magnetism of two-dimensional dipolar spin ices (2D-DSI) is an exploding and innovative field of science. Recent developments in 2D-DSI research concern the defects also known as ``magnetic monopoles'' connected by a Dirac string. The ultimate goal of 2D-DSI research is creation of a magnetic analog of Spintronics using monopoles and Dirac strings as acting elements. Main stream of investigations on 2D-DSI concerns the behavior of unbound magnetic monopoles with vanishing tension of Dirac strings. Here, it is shown that in the regime of bound monopoles (BM) with non-vanishing Dirac string tension one-dimensional Dirac strings rather than point-like monopoles are effective degrees of freedom [1]. Particularly, BMs do not obey the Coulomb law and can be attracted or repulsed depending on the tension-to-mass ratio. Dirac string tension in strongly coupled 2D-DSI is found to be a fundamental quantity, which is bounded by the fine-structure constant and lattice specific parameters only. A measurable prediction of path-time dependence of endpoints of stretched and then released Dirac strings is made and verified via simulations. It is demonstrated that this kind of string dynamics may be used to achieve spontaneous currents of confined monopoles and to store energy. Interestingly, the current duration can be increased by geometrical means, e.g. increasing the length of a sample as will be shown in an experimental demonstration. Nanoscale realization of this effect will open novel technological avenues and change our understanding of magnetism in 2D-DSI fundamentally. [1] E. Y. Vedmedenko, Phys. Rev. Lett. 116, 077202 (2016). [Preview Abstract] |
Thursday, March 16, 2017 1:03PM - 1:39PM |
S22.00004: Artificial magnets as model systems : from the fragmentation of magnetization to the 6-vertex model Invited Speaker: Benjamin Canals Complex architectures of nanostructures are routinely elaborated using bottom-up or nanofabrication processes.\\ \\This technological capability allows scientists to engineer materials with properties that do not exist in nature, but also to manufacture model systems to explore fundamental issues which appeared in condensed matter physics.\\ \\One- and two-dimensional frustrated arrays of magnetic nanostructures are one class of systems for which theoretical predictions can now be tested experimentally.\\ \\These systems have been the subject of intense research in the last few years and have allowed the investigation of a rich physics and fascinating phenomena, such as the exploration of the extensively degenerate ground-state manifolds of spin ice systems, the evidence of new magnetic phases in purely two-dimensional lattices, and the observation of pseudo-excitations involving classical analogues of magnetic charges.\\ \\This talk aims at providing two examples of two-dimensional artificial magnets which allow to probe the low energy manifolds of two exotic Ising systems.\\ \\The first one is related to the seminal 6-vertex model and shows that it is possible to perform a scan through the 6-vertex model phase diagram with an appropriately designed artificial magnet [1].\\ \\In particular, the symmetric point of the square ice is recovered, providing with the opportunity to study the signatures of an algebraic Coulomb spin liquid.\\ \\Because of the experimental procedure used to reach the low energy manifold, quasi-particles are trapped in this disordered manifold, pointing to the need of thermal systems, but also emphasizing that these systems may be well suited to study out of equilibrium relaxation of monopole-monopole pairs in a near future.\\ \\The second one refers to a recent proposal, the fragmentation of magnetization [2], in an Ising kagom\'e model.\\ \\Here, we show it is possible to observe this intriguing phenomena, which corresponds to the splitting of the local degree of freedom into two channels, one ordering at low effective temperatures, in an AF all-in all-out ordering despite the ferromagnetic nature of the system, the other, building a Coulomb-like low energy manifold, inside which the magnetic equivalent of the Kirchhoff law at each node of the kagom\'e lattice is fulfilled [3].\\ \\ \noindent [1] Y. Perrin, B. Canals, N. Rougemaille, Nature, 2016 (to be published).\\ \\ \noindent [2] M. E. Brooks-Bartlett, S. T. Banks, L. D. C. Jaubert, A. Harman-Clarke, and P. C. W. Holdsworth, Phys. Rev. X, 4, 011007 (2014).\\ \\ \noindent [3] B. Canals, I. A. Chioar, V.-D. Nguyen, M. Hehn, D. Lacour, F. Montaigne, A. Locatelli, T. O. Mentes, B. S. Burgos and N. Rougemaille, Nat. Comm. 7, 11446 (2016).\\ [Preview Abstract] |
Thursday, March 16, 2017 1:39PM - 2:15PM |
S22.00005: Creation and applications of reconfigurable artificial magnetic charge ices Invited Speaker: Zhi-Li Xiao Artificial spin ices are arrays of lithographically created nanoscale single domain bar magnets. They are introduced to mimic the behavior of naturally occurring “frustrated” magnetic materials and enable the study of geometrical frustration by design and through direct observation. Among them, the artificial square spin ice consisting a square lattice with the bar magnets perpendicular to its sides is the first and the most investigated artificial ice system. It has proven difficult to achieve tailored long-range ordering of its diverse configurations including the degenerate ground states. Instead of focusing on the spins, we “broke up” each magnetic bar into a positive and negative magnetic charge and designed an artificial spin structure that produces a magnetic charge ice with the same charge distributions as those of the conventional square spin ice but with reconfigurable charge configurations. By precisely manipulating the single artificial spin/charge using a tip of magnetic force microscope, we demonstrated ‘write-read-erase’ multi-functionality at room temperature. We also applied these reconfigurable artificial magnetic charge ices to control the properties of other material systems, as shown by our recently realized in-situ tunable magneto-transport properties in a superconducting-film/magnetic-charge-ice hybrid.\\ \\Reference:\newline Yong-Lei Wang, Zhi-Li Xiao, Alexey Snezhko, Jing Xu, Leonidas E. Ocola, Ralu Divan, John E. Pearson, George W. Crabtree, Wai-Kwong Kwok, “Rewritable artificial magnetic charge ice,” Science 352, 962 (2016). [Preview Abstract] |
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