Volume 127, Number 4, August 2019
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||26 September 2019|
Molecular-orbital representation of generic flat-band models
Department of Physics, University of Tsukuba - 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan
Received: 19 April 2019
Accepted: 5 August 2019
We develop a framework to describe a wide class of flat-band models, with and without a translational symmetry, by using “molecular orbitals” introduced in a prior work (Hatsugai Y. and Maruyama I., EPL, 95 (2011) 20003). Using the molecular-orbital representation, we shed new light on the band-touching problem between flat and dispersive bands. We show that the band touching occurs as a result of collapse, or the linearly dependent nature, of molecular orbitals. Conversely, we can gap out the flat bands by modulating the molecular orbitals so that they do not collapse, which provides a simple prescription to construct models having a finite energy gap between flat bands and dispersive bands.
PACS: 71.10.-w – Theories and models of many-electron systems / 71.23.-k – Electronic structure of disordered solids
© EPLA, 2019
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