Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session Y3: Skyrmions in Chiral MagnetsInvited
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Sponsoring Units: DCMP GMAG Chair: Nandini Trivedi, Ohio State University Room: Ballroom III |
Friday, March 18, 2016 11:15AM - 11:51AM |
Y3.00001: INVITED ABSTRACT WITHDRAWN |
Friday, March 18, 2016 11:51AM - 12:27PM |
Y3.00002: Experimental Studies of Berry Phase Effects and Collective Excitations in Skyrmion Materials Invited Speaker: Christian Pfleiderer The emergence, stability and decay of skyrmions in chiral magnets and the associated emergent electrodynamics are reviewed. The non-zero topological winding, which corresponds to precisely one quantum of emergent magnetic flux, mediates an extremely efficient coupling between the conduction electrons and the magnetic properties. This emergent flux leads to a topological Hall signal, spin transfer torques at ultra-low current densities and emergent electric fields. Additionally skyrmions are characterised by an exceptional stability, which cannot be simply suppressed under large hydrostatic pressures or doping. In fact, measurements of the Hall effect suggest the survival of non-trivial topological winding akin that of the skyrmion lattice in a non-Fermi liquid regime at high pressures, where neutrons scattering suggests the absence of long-range magnetic order. The topological unwinding of skyrmions, which involves emergent magnetic monopoles, may be at the heart of the loss of long-range order. [Preview Abstract] |
Friday, March 18, 2016 12:27PM - 1:03PM |
Y3.00003: Skyrmions in chiral magnets with Rashba and Dresselhaus Spin-Orbit Coupling Invited Speaker: Mohit Randeria Studies of skyrmions in chiral magnets have focused largely on systems with broken bulk inversion and a Dzyaloshinkii-Moriya interaction (DMI) of the Dresselhaus form. The skyrmion crystal is then stable only in a small regime with easy-axis anisotropy. I will show how skyrmion crystal phases can be stabilized over a much larger region of field and anisotropy down to zero temperature in systems with a Rashba DMI that break surface inversion or mirror symmetry [1,2]. Increasing the ratio of Rashba to Dresselhaus DMI leads to a progressively larger domain of stability for skyrmions, especially in the easy-plane anisotropy regime. The spin texture and topological charge density then develop nontrivial spatial structures, different from conventional skyrmions, with a quantized topological charge given by a Chern number. Our theoretical results predict how tuning the Rashba spin orbit coupling and magnetic anisotropy can help stabilize skyrmion phases in thin films, surfaces, interfaces and bulk magnets with broken mirror symmetry. [1] J. Rowland, S. Banerjee, and M. Randeria, arXiv:1509.07508v2. [2] S. Banerjee, J. Rowland, O. Erten, and M. Randeria, PRX 4, 031045 (2014). [Preview Abstract] |
Friday, March 18, 2016 1:03PM - 1:39PM |
Y3.00004: Skyrmions in frustrated magnets Invited Speaker: Shizeng Lin A skyrmion in magnets or magnetic skyrmion is a stable spin texture with nontrivial topology and behaves like a particle at mesoscale. To stabilize a skyrmion, it is required to have a characteristic length scale, which can be introduced by competing interactions. Recently skyrmion lattice has been observed experimentally in chiral magnets without inversion symmetry, where the skyrmions are stabilized by the competition between the exchange and Dzyaloshinskii-Moriya interactions. The skyrmions in chiral magnets have been studied actively and have been demonstrated to be promising for applications. These skyrmions share qualitatively similar properties in metals, semiconductors and insulators and can be described by a simple universal Hamiltonian. Skyrmions can also be stabilized in frustrated magnets with inversion symmetry. In the talk, we will present a general Ginzburg-Landau theory for the skyrmions in the frustrated magnets. We will discuss their unusual properties in comparison to those in chiral magnets. Finally we will also discuss the conditions for the stabilization of skyrmions. [Preview Abstract] |
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