Abstract
Based on the elementary band representations(EBR),many topologically trivial materials are classified as unconventional ones(obstructed atomic limit),where the EBR decomposition for a set of electronic states is not consistent with atomic valence-electron band representations.In the work,we identify that the unconventional nature can also exist in phonon spectra,where the EBR decomposition for a set of well-separated phonon modes is not consistent with atomic vibration band representations(ABR).The unconventionality has two types:type Ⅰ is on an empty site;and type Ⅱ is on an atom site with non-atomic vibration orbitals.The unconventionality is described by the nonzero real-space invariant at the site.Our detailed calculations show that the black phosphorus(BP)has the type Ⅰ unconventional phonon spectrum,while 1H-MoSe2 has the type Ⅱ one,although their electronic structures are also unconventional.Accordingly,the obstructed phonon modes are obtained for two types of unconventional phonon spectra.
基金项目
国家自然科学基金(11974395)
国家自然科学基金(12188101)
中国科学院战略规划重点项目(XDB33000000)
National Key Research and Development Program of Chain(2022YFA1403800)
Center for Materials Genome()
维普
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