Phonon softening, chaotic motion, and order-disorder transition in Sn/Ge(111).
The phonon dynamics of the Sn/Ge(111) interface is studied using high-resolution helium atom scattering and first-principles calculations. At room temperature we observe a phonon softening at the Kmacr; point in the (sqrt[3]xsqrt[3])R30 degrees phase, associated with the stabilization of a (3x3) phase at low temperature. That phonon band is split into three branches in the (3x3) phase. We analyze the character of these phonons and find out that the low- and room-temperature modes are connected via a chaotic motion of the Sn atoms. The system is shown to present an order-disorder transition.
Farías
D
D
Departamento de Física de la Materia Condensada and Instituto Nicolás Cabrera, Universidad Autónoma, 28049 Madrid, Spain.
Kamiński
W
W
Lobo
J
J
Ortega
J
J
Hulpke
E
E
Pérez
R
R
Flores
F
F
Michel
E G
EG