A general group theoretical method to unfold band structures and its application

Abstract

We present a general method to unfold energy bands of supercell calculations to a primitive Brillouin zone using group theoretical techniques, where an isomorphic factor group is introduced to connect the primitive translation group with the supercell translation group via a direct product. Originating from the translation group symmetry, our method gives a uniform description of unfolding approaches based on various basis sets and therefore should be easy to implement in both tight-binding models and existing ab initio code packages using different basis sets. This makes the method applicable to a variety of problems involving the use of supercells, such as defects, disorder and interfacial reconstructions. As a realistic example, we calculate electronic properties of a monolayer FeSe on SrTiO 3 in checkerboard and collinear antiferromagnetic spin configurations, illustrating the potential of our method.

Quantum Unfolding: A program for unfolding electronic energy bands of materials

“…[20]. In this method, the unfolding weight is obtained as the expectation value of a projection operator…”

“…Popescu et al also proposed a method to unfold energy bands, and applied the method to study random alloys [5,6]. Based on the translational symmetry group, recently, we have built a general group theoretical method to unfold energy band structures [20]. At the same time, the energy bands unfolding code is actively constructed.…”

First-principles study of magnetic frustration in FeSe epitaxial films onSrTiO3

“…Many efforts have also been devoted from a theoretical standpoint. [22][23][24][25][26][27][28][29][30] In our previous calculations, 22 the similar electronic structures of monolayer and bilayer FeSe on undoped SrTiO 3 suggested that the superconductivity would occur at the first layer of FeSe epitaxial film or at the interface. Xiang et al studied the influence of the screening effect of a ferroelectric phonon of the substrate on the Cooper pairs in the FeSe layer.…”

Phonon Unfolding : A program for unfolding phonon dispersions of materials

“…Recently, the rapidly developed electron energy bands unfolding methods [9][10][11][12][13][14][15][16][17][18][19][20][21][22] stimulated the study of phonon unfolding methods [21][22][23][24]. In one of our previous papers [24], we proposed a generalized calculation scheme to unfold phonon dispersions, which can be applied to atomic systems with any kind of translational symmetry broken.…”