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SUMMARY:Quantum Order-by-Disorder Near Criticality and the Secret of the P
 artially Ordered Phase of MnSi - Frank Kruger\, University of St Andrews
DTSTART:20120524T131500Z
DTEND:20120524T141500Z
UID:TALK37398@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:The vicinity of quantum phase transitions has proven fertile g
 round in the search for new quantum phases. We propose a physically motiva
 ted and unifying description of phase reconstruction near metallic quantum
 -critical points using the idea of quantum order by disorder. Certain defo
 rmations of the Fermi surface associated with the onset of competing order
  enhance the phase space available for low-energy\, particle-hole fluctuat
 ions and self-consistently lower the free energy. Applying the notion of q
 uantum order by disorder to the itinerant helimagnet MnSi\, we show that\,
  near the quantum critical point\, fluctuations lead to an increase of the
  spiral ordering wave vector and a reorientation away from the lattice-fav
 ored \ndirections. The magnetic ordering pattern in this fluctuation-drive
 n phase is found to be in excellent agreement with the neutron scattering 
 data in the partially ordered phase of MnSi.    
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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