ELFT HÍRADÓ

[Balazs Dora <dora AT kapica.phy.bme.hu>]

                RENDKIVULI szeminarium:

           Roderich Moessner (MPIPKS, Dresden)


              Magnetic monopoles in spin ice


Kivonat:
Fractionalisation is a counterintuitive phenomenon, in which an
elementary particle appears to break into two independent entities.  A
celebrated example of this is spin-charge separation, in which an
electron's magnetic (spin) and electric (charge) properties appear to
become independent degrees of freedom.

Spin ice materials -- Dy_2 Ti_2 O_7 and Ho_2 Ti_2 O_7 -- provide a rare
instance of fractionalisation in three dimensions. Their
elementary excitations result from the fractionalisation of their
microscopic magnetic moments; these excitations can be thought of as
magnetic monopoles [1].

This talk presents an elementary introduction to theoretical concepts
for, and experiment studies of, spin ice. It focuses on the unique
signatures of the peculiar nature of its excitations.  These include
unusual neutron scattering structure factors [2-4], dynamical arrest and
long lived non-equilibrium metastable states [5], as well as a response
to external magnetic fields that promotes spin ice as a new type of
magnetic system which has been called a magnetic plasma, a magnetic
Coulomb liquid, or  a magnetolyte [6]. This talk reviews several of
these striking phenomena, and discusses open questions and future
perspectives.

[1] C. Castelnovo et al., Nature 451, 42 (2008).
[2] H. Kadowaki et al., J. Phys. Soc. Jpn. 78, 103706-1 (2009).
[3] T. Fennell et al., Science 326, 415 (2009).
[4] D. J. P. Morris et al., Science 326, 411 (2009).
[5] C. Castelnovo et al., Phys. Rev. Lett. 104, 107201 (2009).
[6] S. T. Bramwell et al., Nature 461, 956 (2009).


Helye: BME Fizikai Intezet, Elmeleti Fizika Tanszek
       Budafoki ut 8. F-epulet, III. lepcsohaz, magasfoldszint
       Szeminariumi szoba

       Ideje: 2012. junius 12. kedd, 15:15.

       Minden erdeklodot szivesen latunk.


                                                Dora Balazs