High-energy spin and charge excitations in electron-doped copper oxide superconductors.
The evolution of electronic (spin and charge) excitations upon carrier doping is an extremely important issue in superconducting layered cuprates and the knowledge of its asymmetry between electron- and hole-dopings is still fragmentary. Here we combine X-ray and neutron inelastic scattering measurements to track the doping dependence of both spin and charge excitations in electron-doped materials. Copper L3 resonant inelastic X-ray scattering spectra show that magnetic excitations shift to higher energy upon doping. Their dispersion becomes steeper near the magnetic zone centre and they deeply mix with charge excitations, indicating that electrons acquire a highly itinerant character in the doped metallic state. Moreover, above the magnetic excitations, an additional dispersing feature is observed near the Γ-point, and we ascribe it to particle-hole charge excitations. These properties are in stark contrast with the more localized spin excitations (paramagnons) recently observed in hole-doped compounds even at high doping levels.
SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan.
K
K
Ishii
Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan.
M
M
Fujita
Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan.
T
T
Sasaki
CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy.
M
M
Minola
CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy.
G
G
Dellea
CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy.
C
C
Mazzoli
European Synchrotron Radiation Facility, 6 rue Jules Horowitz, Grenoble F-38043, France.
K
K
Kummer
CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy.
G
G
Ghiringhelli
CNR-SPIN and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, Milano I-20133, Italy.
L
L
Braicovich
1] Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan [2].
T
T
Tohyama
Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan.
K
K
Tsutsumi
Institute for Materials Research, Tohoku University, Katahira, Sendai 980-8577, Japan.
K
K
Sato
Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan.
R
R
Kajimoto
Research Center for Neutron Science and Technology, Comprehensive Research Organization for Science and Society, Tokai, Ibaraki 319-1106, Japan.
K
K
Ikeuchi
Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Ibaraki 305-0801, Japan.
K
K
Yamada
1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
M
M
Yoshida
School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
M
M
Kurooka
1] SPring-8, Japan Atomic Energy Agency, Sayo, Hyogo 679-5148, Japan [2] School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan.
J
J
Mizuki