1201.5425 (Taichi Terashima et al.)

Large homogeneous mass enhancement in the rattling-induced
superconductor KOs$_2$O$_6$    [PDF]

Taichi Terashima, Nobuyuki Kurita, Andhika Kiswandhi, Eun-Sang Choi, James S. Brooks, Kota Sato, Jun-ichi Yamaura, Zenji Hiroi, Hisatomo Harima, Shinya Uji

We have determined the Fermi surface in KOs$_2$O$_6$ ($T_c$ = 9.6 K and
$B_{c2} \sim$ 32 T) via de Haas-van Alphen (dHvA) oscillation measurements and
a band structure calculation. We find effective masses up to 26(1) $m_e$ ($m_e$
is the free electron mass), which are unusually heavy for compounds where the
mass enhancement is mostly due to electron-phonon interactions. Orbit-resolved
mass enhancement parameters $\lambda_{dHvA}$ are large but fairly homogeneous,
concentrated in the range 5 -- 8. We discuss origins of the large homogeneous
mass enhancement in terms of rattling motion of the K ions.

View original: http://arxiv.org/abs/1201.5425