Electronic Crystal State in a Hole Doped Cuprate
C. Lupiena , Y. Kohsakab, T. Hanaguric, M. Azumad , M. Takanod , H. Takagie , and J. C. Davisb
a
Département de Physique, Université de Sherbrooke, Sherbrooke, Qc J1K 2R1, Canada
LASSP, Department of Physics, Cornell University, Ithaca, NY 14853, USA
c
Magnetic Materials Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
d
Institute of Chemical Research, Kyoto University, Uji, Kyoto 601-0011, Japan
e
Department of Advanced Materials Science,University of Tokyo, Kashiwa, Chiba 277-8651, Japan
b
In cuprate superconductors, the low doping region shows many different phases namely Mott antiferromagnetic insulator, pseudogap and superconducting phases. The pseudogap phase in the lightly
doped regime is rich in peculiar phenomena which may be closely related to the strong correlation effects
in cuprates. We have carried out scanning tunneling microscopy/spectroscopy (STM/STS) on Ca 2−x Nax CuO2 Cl2 single crystals (x = 0.08 ∼ 0.12) to visualize the spatial variation of the electronic states in the
zero temperature pseudogap phase. We found ’checkerboard’ local density of states (LDOS) modulation
which is characterized by the tiling of the commensurate 4a × 4a electronic entity. Each 4a × 4a unit cell
carries intricate internal structures which include 4a/3 × 4a/3 LDOS modulation. The modulation amplitudes of these components are strongly energy dependent but the periodicities are energy independent,
over the doping range studied. This suggests that the zero temperature pseudogap phase is associated
with the electronic order or electronic crystal which manifests itself as the observed ‘checkerboard’.
Reference:T. Hanaguri et al., Nature 430, 1001 (2004).
Sorting category: Ba Superconductivity
Keywords: scanning tunneling microscopy/spectroscopy, cuprate
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