Events in Physics
CMP Seminar - Jonathan Morris (Helmholtz Zentrum Berlin)
Recent proposals in condensed matter physics that magnetic monopoles can appear as emergent quasiparticles have attracted wide levels of interest. Dirac’s original picture of magnetic monopoles had them connected to strings through which magnetic flux flowed. Here we report studies into a system called Spin Ice, where spins obey “ice rule” of 2 spins into and 2 spins out of their tetrahedron. In these materials it has been predicted that strings of spins form via a 3D Kasteleyn transition [1]. The geometry of spin-ice allows for net magnetic charge (magnetic monopoles) to form where “ice rules” are broken at the tips of the strings [2]. Here the experimental pieces of evidence for these strings and magnetic monopoles will be discussed [3-6] along with some aspects to the methods used and the background to the problem.
1. L.D.C. Jaubert, et al. Phys Rev. Lett. 100, 067207 (2008)
2. C. Castelnovo, et al. Nature 451, 42 (2008)
3. D.J.P. Morris, et al. Science 326, 411 (2009)
4. T. Fennell, et al. Science 326, 415 (2009)
5. S.T. Bramwell, et al. Nature 461, 956 (2009)
6. H. Kadowaki, et al. J. Phys. Soc. Jpn. 78, 103706 (2009)