Evidence for ubiquitous strong electron-phonon coupling in high-temperature superconductors.
Coupling between electrons and phonons (lattice vibrations) drives the formation of the electron pairs responsible for conventional superconductivity. The lack of direct evidence for electron-phonon coupling in the electron dynamics of the high-transition-temperature superconductors has driven an intensive search for an alternative mechanism. A coupling of an electron with a phonon would result in an abrupt change of its velocity and scattering rate near the phonon energy. Here we use angle-resolved photoemission spectroscopy to probe electron dynamics-velocity and scattering rate-for three different families of copper oxide superconductors. We see in all of these materials an abrupt change of electron velocity at 50-80 meV, which we cannot explain by any known process other than to invoke coupling with the phonons associated with the movement of the oxygen atoms. This suggests that electron-phonon coupling strongly influences the electron dynamics in the high-temperature superconductors, and must therefore be included in any microscopic theory of superconductivity.
Lanzara
A
A
Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA.
Bogdanov
P V
PV
Zhou
X J
XJ
Kellar
S A
SA
Feng
D L
DL
Lu
E D
ED
Yoshida
T
T
Eisaki
H
H
Fujimori
A
A
Kishio
K
K
Shimoyama
J I
JI
Noda
T
T
Uchida
S
S
Hussain
Z
Z
Shen
Z X
ZX