11 research outputs found
Pressure dependence of the spin dynamics around a quantum critical point : An inelastic neutron scattering study of Ce0.87La0.13Ru2Si2
Inelastic neutron scattering experiments performed on a single crystal of the
antiferromagnetic compound CeLaRuSi under applied
pressures of up to 5 kbar are reported. A quantum critical point is reached at
around 2.6 kbar where long-range magnetic order disappears. The variation of
the characteristic energy scales with respect to temperature and pressure is
followed and found to saturate in the ordered phase.Comment: 14 pages (6 figures
Enhanced Impurity Scattering due to Quantum Critical Fluctuations
It is shown on the basis of the lowest order perturbation expansion with
respect to critical fluctuations that the critical fluctuations give rise to an
enhancement of the potential scattering of non-magnetic impurities. This
qualitatively accounts for the enhancement of the resistivity due to impurities
which has been observed in variety of systems near the quantum critical point,
while the higher order processes happen to give much larger enhancement as seen
from the Ward identity arguments. The cases with dynamical critical exponent
=2 and =3 are discussed explicitly.Comment: Submitted to J. Phys. Soc. Jpn. on 27 September, 200
Spin Fluctuation Theory for Quantum Tricritical Point Arising in Proximity to First-Order Phase Transitions: Applications to Heavy-Fermion Systems, YbRh2Si2, CeRu2Si2, and beta-YbAlB4
We propose a phenomenological spin fluctuation theory for antiferromagnetic
quantum tricritical point (QTCP), where the first-order phase transition
changes into the continuous one at zero temperature. Under magnetic fields,
ferromagnetic quantum critical fluctuations develop around the
antiferromagnetic QTCP in addition to antiferromagnetic ones, which is in sharp
contrast with the conventional antiferromagnetic quantum critical point. For
itinerant electron systems,} we show that the temperature dependence of
critical magnetic fluctuations around the QTCP are given as chiQ \propto
T^{-3/2} (chi0\propto T^{-3/4}) at the antiferromagnetic ordering
(ferromagnetic) wave number q=Q (q=0). The convex temperature dependence of
chi0^{-1} is the characteristic feature of the QTCP, which is never seen in the
conventional spin fluctuation theory. We propose that the general theory of
quantum tricriticality that has nothing to do with the specific Kondo physics
itself, solves puzzles of quantum criticalities widely observed in
heavy-fermion systems such as YbRh2Si2, CeRu2Si2, and beta-YbAlB4. For
YbRh2Si2, our theory successfully reproduces quantitative behaviors of the
experimental ferromagnetic susceptibility and the magnetization curve by
choosing the phenomenological parameters properly. The quantum tricriticality
is also consistent with singularities of other physical properties such as
specific heat, nuclear magnetic relaxation time 1/T_1T, and Hall coefficient.
For CeRu2Si2 and beta-YbAlB4, we point out that the quantum tricriticality is a
possible origin of the anomalous diverging enhancement of the uniform
susceptibility observed in these materials.Comment: 17 pages, 10 fugures, to appear in Journal of the Physical Society of
Japan Vol.78 No.