Pronounced enhancement of the lower critical field and critical current deep in the superconducting state of PrOs 4 Sb 12
T. Cichorek, A. C. Mota, F. Steglich, N. A. Frederick, W. M. Yuhasz, M. B. Maple
Abstract
We have observed an unexpected enhancement of the lower critical field
H
c1
(T)
and the critical current
I
c
(T)
deep in the superconducting state below
T≈0.6
K (
T/
T
c
≈0.3
) in the filled skutterudite heavy fermion superconductor PrOs
4
Sb
12
. From a comparison of the behavior of
H
c1
(T)
with that of the heavy fermion superconductors U
1−x
Th
x
Be
13
and UPt
3
, we speculate that the enhancement of
H
c1
(T)
and
I
c
(T)
in PrOs
4
Sb
12
reflects a transition into another superconducting phase that occurs below
T/
T
c
≈0.3
. An examination of the literature reveals unexplained anomalies in other physical properties of PrOs
4
Sb
12
near
T/
T
c
≈0.3
that correlate with the features we have observed in
H
c1
(T)
and
I
c
(T)
.