Noncompact atomic insulators
File(s)PhysRevB.104.L201114.pdf (681.3 KB)
Published version
Author(s)
Schindler, Frank
Bernevig, B Andrei
Type
Journal Article
Abstract
We study the conditions for Bloch bands to be spanned by symmetric and strictly compact Wannier states that have zero overlap with all lattice sites beyond a certain range. Similar to the characterization of topological insulators in terms of an algebraic (rather than exponential) localization of Wannier states, we find that there may be impediments to the compact localization even of topologically “trivial” obstructed atomic insulators. These insulators admit exponentially localized Wannier states centered at unoccupied orbitals of the crystalline lattice. First, we establish a sufficient condition for an insulator to have a compact representative. Second, for
C
2
rotational symmetry, we prove that the complement of fragile topological bands cannot be compact, even if it is an atomic insulator. Third, for
C
4
symmetry, our findings imply that there exist fragile bands with zero correlation length. Fourth, for a
C
3
-symmetric atomic insulator, we explicitly derive that there are no compact Wannier states overlapping with less than 18 lattice sites. We conjecture that this obstruction generalizes to all finite Wannier sizes. Our results can be regarded as the stepping stone to a generalized theory of Wannier states beyond dipole or quadrupole polarization.
C
2
rotational symmetry, we prove that the complement of fragile topological bands cannot be compact, even if it is an atomic insulator. Third, for
C
4
symmetry, our findings imply that there exist fragile bands with zero correlation length. Fourth, for a
C
3
-symmetric atomic insulator, we explicitly derive that there are no compact Wannier states overlapping with less than 18 lattice sites. We conjecture that this obstruction generalizes to all finite Wannier sizes. Our results can be regarded as the stepping stone to a generalized theory of Wannier states beyond dipole or quadrupole polarization.
Date Issued
2021-11-29
Date Acceptance
2021-11-09
Citation
Physical Review B, 2021, 104 (20), pp.1-5
ISSN
2469-9950
Publisher
American Physical Society (APS)
Start Page
1
End Page
5
Journal / Book Title
Physical Review B
Volume
104
Issue
20
Copyright Statement
©2021 American Physical Society
Identifier
http://dx.doi.org/10.1103/physrevb.104.l201114
Publication Status
Published
Article Number
L201114
Date Publish Online
2021-11-29