Anisotropic flat band and charge density wave in quasi-one-dimensional indium telluride

Quasi-one-dimensional (quasi-1D) monochalcogenide compounds exhibit a strong in-plane anisotropy in their electronic band structure, which originates from their low crystallographic symmetry and provides an ideal platform for exploring collective electron behavior in confined systems. Here, we provide direct experimental evidence of electronic flat band near the Fermi level in quasi-1D InTe, using a combination of angle-resolved photoemission spectroscopy (ARPES), and density-functional theory (DFT). This flattened band extends about 0.4 ^-1 one dimensionally in k-space area around the M point according to ARPES and DFT. Using scanning tunneling microscopy, we found a modulation in the density of states along the In¹⁺ atoms, with a wavelength of two times the lattice constants. This periodic modulation order could be results from a Peierls instability, in which a spatial lattice distortion opens an electronic gap at the Fermi energy. Such quasi-1D InTe crystals provide a platform for fundamental research and future applications which relies on collective electronic behavior of a quasi-1D semiconductor.