Observation of electronic inhomogeneity and charge density wave in a bilayer La$_{1.36}$Sr$_{1.64}$Mn$_2$O$_7$ single crystal

TL;DR

This study used scanning tunneling microscopy to reveal charge density wave patterns and electronic inhomogeneity on the surface of a bilayer manganite crystal, highlighting intrinsic spatial modulations.

Contribution

It demonstrates the presence of a charge density wave in La$_{1.36}$Sr$_{1.64}$Mn$_2$O$_7$ and links it to competing interactions between localized and itinerant electrons.

Findings

Stripe-like LDOS modulation with 1.6 Å wavelength

Charge density wave not due to Fermi surface nesting

Intrinsic spatial modulations explained by stripe model

Abstract

We employed a scanning tunneling microscope to image the (001) surface topography and local density of states (LDOS) in La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (x=0.32, LSMO) single crystals below the Curie temperature (T$_C$ = 120 K). The LDOS maps revealed a stripe-like modulation propagating along the tetragonal a axis with a wavelength of about 1.6 \AA, which is indicative of a charge density wave (CDW). The observed CDW in the x=0.32 sample is far from the Fermi surface nesting instability as compared with the data of angle resolved photoemission spectroscopy in an x=0.40 sample. The stripe model developed previously for cuprates can explain the observed CDW in our LSMO sample, indicating that competing interactions between localized and itinerant phases are the origin of the spatial modulations present intrinsically in cuprates and manganites.