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PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-2094
DTSTART:20110131T220000Z
DURATION:PT1H0M0S
DTSTAMP:20260419T010656Z
LAST-MODIFIED:20110127T194327Z
LOCATION:5280 Chamberlin
SUMMARY:Realistic quantum critical points\, Condensed Matter Theory Gr
 oup Seminar\, Munehisa Matsumoto\, University of California-Davis
DESCRIPTION:Quantum criticality has been discussed to play a key role 
 in interesting phenomena in strongly-correlated systems\, such as high
 -<i>T<sub>c</sub></i> superconductivity in cuprates (here <i>T<sub>c</
 sub></i> is the superconducting transition temperature)\, recently-dis
 covered iron pnictides/chalcogenides\, and heavy-fermion materials. In
  the main part of the talk I will show how the magnetic quantum critic
 al point (QCP) in heavy-fermion materials can be quantitatively predic
 ted by combining electronic-stricture calculations based on local-dens
 ity approximation (LDA) and dynamical-mean field theory (DMFT) for the
  LDA-derived effective low-energy Hamiltonian. We utilize state-of-the
 -art continuous-time quantum Monte Carlo method to solve the impurity 
 problem in DMFT formulated on the basis of localized f-electrons\, whi
 ch enables us to obtain numerically-exact solutions at low temperature
 s down to <i>O</i>(1) [K] within DMFT. Thus we reach at a good positio
 n to address the quantum critical point quantitatively and we find the
  followings: 1) striking multiple quantum critical points are found in
  a realistic phase diagram for Plutonium-based compounds\, which is at
 tributed to the strong-coupling nature of the effective Kondo-lattice 
 model. PuCoGa<sub>5</sub>\, with the highest <i>T<sub>c</sub></i> = 18
 .5 [K] among f-electron based materials\, is found be located in the p
 roximity to the third QCP [1]. 2) CeCoIn<sub>5</sub>\, which has the h
 ighest <i>T<sub>c</sub></i> = 2.3 [K] among Cerium-based heavy-fermion
  compounds\, its parent material CeIn<sub>3</sub>\,
\nand its new two-
 dimensional (2D) analogue CePt<sub>2</sub>In<sub>7</sub> are concentra
 ted around a QCP where CeCoIn<sub>5</sub> is found to be right on top 
 of QCP. The reason the most 2D one does not come closest to QCP is att
 ributed to the subtlety in the competition between the dimensionality 
 and hybridization effects along the c-axis [2]. In the final part of t
 he talk I will discuss the possible subtle nature of what has
\nbeen c
 alled QCP\, which still challenges realistic numerics but careful nume
 rical analyses of an effective field theory [3] tells us QCP might not
  truly be critical. Possible consequence for having the resonating val
 ence bond state around what has been QCP [4] is revisited.
\n<br>
\n<b
 r>
\nReferences
\n<br>
\n[1] MM\, Q. Yin\, J. Otsuki\, S. Y. Savrasov\
 , preprint [arXiv:1101.1582].<br>
\n[2] MM\, M. J. Han\, J. Otsuki\, S
 . Y. Savrasov\, Phys. Rev. B 82\, 180515(R) (2010) [arXiv:1004.5457].<
 br>
\n[3] A. B. Kuklov\, MM\, N. V. Prokof'ev\, B. V. Svistunov\, M. T
 royer\, Phys. Rev. Lett. 101\, 050405 (2008) [arXiv:0805.4334].<br>
\n
 [4] P. Coleman and N. Andrei\, J. Phys.: Condens. Matter 1\, 4057 (199
 0).
URL:https://www.physics.wisc.edu/events/?id=2094
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