Abstracts
O1.8
Condensation of helium in a silica aerogel: a realization of the
athermal Random Field Ising Model
Geoffroy Jacques Aubry(1), Victor Doebele(1), Edouard Kierlik(2),
Panayotis Spathis(1), Pierre-Etienne Wolf(1)
1) Institut Neel, Universitee Grenoble Alpes/CNRS
2) LPTMC, Universite Pierre et Marie Curie/CNRS
We experimentally study the condensation of
4
He in light silica aerogels to
probe the effect of dilute disorder on a first order phase transition. Using light
scattering to measure the fluid state on a local scale, we show that our system is
well described by the, out-of-equilibrium, athermal, Random Field Ising Model
(RFIM) introduced by Sethna et al (PRL 70, 3347, 1993). Specifically, we evidence
the two phenomena predicted by this model.
i) A disorder driven critical point (Aubry et al, PRL 113, 085301, 2014)
ii) A microscopic Return Point Memory along minor hysteresis loops.
Our measurements are the first to demonstrate these two effects in a single
physical system.
O1.9
Quantum degradation of the second order phase transition
S.M. Stishov, A.E. Petrova
Institute for High Pressure Physics of RAS, Troitsk, Russia
The specific heat, magnetization and thermal expansion of single crystals of
antiferromagnetic insulator EuTe, were measured at temperatures down to 2 K
and in magnetic fields up to 90 kOe. The heat capacity and thermal expansion
coefficient reveal
λ
-type anomalies at the second order magnetic phase transition
at low magnetic fields, evolving to simple jumps at high magnetic fields and
low temperatures, well described in a fluctuation free mean-field theory. The
experimental data and the corresponding analysis favor the quantum concept of
effective increasing space dimensionality at low temperatures that suppresses a
fluctuation divergence at a second order phase transition
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