[seminar] HENRIK RONNOW (IF, 14.06., 15 sati)

[IF Seminar]

Poštovani,

Obavještavamo Vas o održavanju seminara na Institutu za fiziku
u ponedjeljak 14. lipnja u standardnom terminu u 15 sati u 
zgradi Mladen Paić, koji će održati Henrik Ronnow sa Ecole 
Polytechnique Fédérale de Lausanne.
Više informacija o predavaču i instituciji možete naći na:
<http://ipmc.epfl.ch/>
<http://lqm.epfl.ch/>

Sažetak predavanja nalazi se u nastavku poruke.

14.06.2010. u 15:00, Predavaonica u zgradi Mladen Paić

                  Experimental quantum magnetism
              - Neutrons in the quasi-particle zoo

                       Prof. Henrik Ronnow

    Institut de Physique de la Matière Condensée, Station 3,
            Ecole Polytechnique Fédérale de Lausanne
                     henrik.ronnow at epfl.ch

The borderline between classical antiferromagnetic (AFM) order and 
quantum fluctuating ground states is illustrated through neutron 
scattering results on selected Cu2+ based materials serving as 
physical realisations of fundamental low-dimensional S=1/2 models. 
In some ways, theoretical description of fully quantum ground states 
as found in spin chains and ladders is currently more advanced than 
for ordered spin clusters, or even the simple 2D square lattice. The 
antiferromagnetically ordered unfrustrated 2D square lattice host 
behavior not explainable by spin-wave theory, and which occur not 
only in the archetypical model system copper-formate-tetra-deuterate 
(CFTD), but also in the undoped parent of the high-Tc superconductor 
YBCO. I believe this effect is related to the so-called resonating 
valence bond (RVB) that Anderson and co-workers propose to describe 
these enigmatic superconductors. While geometrically defined singlet 
correlations are abound in e.g. the Shastry-Sutherland compound 
SrCu2(BO3)2, in which we explore a pressure induced quantum phase 
transition, distinguishing quantum fluctuating RVB from classically 
fluctuating AFM correlations in e.g. kagome lattices remain a 
challenge.

--
Kontakt: Ivica Živković
(voditelji seminara IF-a: Berislav Horvatić & Marko Kralj)