Glasslike two-level systems in minimally disordered mixed crystals.
THz spectroscopy is used to identify a broad distribution of two-level systems, characteristic of glasses, in the substitutional monatomic mixed crystal systems, Ba(1-x)Ca(x)F(2) and Pb(1-x)Ca(x)F(2). In these minimally disordered systems, two-level behavior, which was not previously known to occur, begins at a specific CaF(2) concentration. The concentration dependence, successfully modeled using the statistics of the impurity distribution in the lattice, points to a collective dopant tunneling mechanism.
Wrubel
J P
JP
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501, USA.
Hubbard
B E
BE
Agladze
N I
NI
Sievers
A J
AJ
Fedorov
P P
PP
Klimenchenko
D I
DI
Ryskin
A I
AI
Campbell
J A
JA