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講演者：Dr. Stephane Raymond (Grenoble)

日時： １１月１７日（金）　午後４時半から
場所： 青山学院大学　理工学部（世田谷キャンパス）　一号館　５階　１５３８号室

講演題目： Inelastic Neutron Scattering Near a Quantum Critical Point in Heavy Fermion Compounds
要旨：
Quantum phase transitions have attracted a lot of attention in recent years both on the theoretical and experimental sides. Such transitions occur at zero temperature as a function of an external parameter (magnetic field, pressure, impurity concentration) which drives the system from an ordered to a disordered state. They are generic of many systems : high-T_c superconductors, quantum Ising magnets, quantum Hall systems. Heavy fermion compounds provide the opportunity to study such phenomena since the competition between ordering (via the RKKY interactions) and disordering (via the Kondo singlet formation) can be experimentally easily controlled.

Recent inelastic neutron scattering data obtained on the system Ce_1-xLa_xRu₂Si₂ will be presented. The quantum critical point is experimentally reached either for x=x_c=0.075 or by applying pressure (P_c=2.6 kbar) on the weak antiferromagnetic compound with x=0.13. Relevance to theoretical works will be discussed in particular in the viewpoint of the spin fluctuation approach. Scaling of the dynamical spin susceptibility in ω/T will be addressed. Comparison with available data for the system CeCu_6-xAu_x will also be made.