Manganites

The single-layered half-doped manganite La_0.5Sr_1.5MnO₄ was studied by means of the angle-resolved photoemission spectroscopy, scanning tunneling microscopy (STM), and resistivity measurements. STM revealed a smooth reconstruction-free surface; the density of states, derived from photoemission and tunneling spectroscopy, is in agreement with transport measurements. The found Fermi surface (FS) nesting properties correspond to the known pattern of the charge-orbital ordering (COO), which implies that FS instability is related to the propensity to form a COO state in this system.

Figure. The photoemission intensity, integrated in energy window of 70meV width, centered at 190 meV below Fermi level, is shown in panels (a)–(e) for different excitation energies and light polarizations: (a) linear horizontal, 157 eV, 300 K; (b) linear horizontal, 37 eV, 190 K; (c) linear horizontal, 70 eV, 195 K; (d) linear horizontal, 200 eV, 300 K; (e) linear vertical, 157 eV, 300 K. Contours of the remnant Fermi surface, which consists of a small round electronlike pocket centered at the point and a large square holelike barrel centered at the K point, are presented in panels (a)–(e) by green lines. The calculated susceptibility is shown in panel (f ), and its profile along the high-symmetry directions is shown in (g).

Physical Review Letters (in press)