Thursday's Disorder seminar

[Cond.Matt. & Stat.Mech.Section]

  SEMINAR on  Disorder and strong electron correlations





Thursday, 28 January      -  11:00 a.m.





EULER LECTURE HALL,  Leonardo Building - terrace level





  Michael ZHITOMIRSKY   ( SPSMS, CEA - Grenoble )





"Spin tensor phases in frustrated magnets"





Abstract



Strong geometrical frustration precludes conventional magnetic  
ordering.  A common outcome is a completely disordered spin-liquid  
state  at zero and at low temperatures.  Another interesting  
possibility is a partial breaking of spin rotational symmetry  
described by spin-tensor order parameters.  We shall discuss two  
examples of such unusual symmetry breaking.  The first model example  
is a classical Heisenberg antiferromagnet on a kagome lattice [1].  At  
low temperatures the order by disorder mechanism selects a submanifold  
of planar spin states which are described by non-zero octupole  
moments.  An interesting consequence of such a third-rank tensor order  
parameter is presence of various types of fractional vortices.  The  
second example is a system of weakly coupled spin-1/2 frustrated  
ferromagnetic chains [2].  The high-field transition from the  
saturated phase occurs via condensation of bound magnon pairs.  Such a  
condensate of is described by spin-nematic or second-rank tensor.  We  
develop analytical theory for the bose condensation into nematic state  
and argue that corresponding transition is realized in LiCuVO4.



[1] M. E. Zhitomirsky, Phys. Rev. B {78}, 094423 (2008).

  [2] H. Tsunetsugu and M. E. Zhitomirsky, in progress (2010).