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КОНДЕНСИРОВАННЫЕ СРЕДЫ
Hall coefficient in heavy fermion metals
V. R. Shaginyana,
K. G. Popovb,
S. A. Artamonova a Petersburg Nuclear Physics Institute, RAS
b Komi Science Center, Ural Division, RAS
Аннотация:
Experimental studies of the antiferromagnetic (AF) heavy fermion metal
$\rm YbRh_2Si_2$ in a magnetic field
$B$ indicate the presence of a jump in the Hall coefficient at a magnetic-field tuned quantum state in the zero temperature limit. This quantum state occurs at
$B\ge B_{c0}$ and induces the jump even though the change of the magnetic field at
$B=B_{c0}$ is infinitesimal. We investigate this by using the model of heavy electron liquid with the fermion condensate. Within this model the jump takes place when the magnetic field reaches the critical value
$B_{c0}$ at which the ordering temperature
$T_N(B=B_{c0})$ of the AF transition vanishes. We show that at
$B\to B_{c0}$, this second order AF phase transition becomes the first order one, making the corresponding quantum and thermal critical fluctuations vanish at the jump. At
$T\to0$ and
$B=B_{c0}$, the Grüneisen ratio as a function of temperature
$T$ diverges. We demonstrate that both the divergence and the jump are determined by the specific low temperature behavior of the entropy
$S(T)\propto S_0+a\sqrt T+bT$ with
$S_0$,
$a$ and
$b$ are temperature independent constants.
PACS:
71.10.Hf,
71.27.+a,
74.72.-h Поступила в редакцию: 30.06.2005
Язык публикации: английский