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Topological electromagnetic responses of bosonic quantum Hall, topological insulator, and chiral semimetal phases in all dimensions

Cornell Affiliated Author(s)

Author

Matthew Lapa
Chao-Ming Jian
Peng Ye
Taylor Hughes

Abstract

We calculate the topological part of the electromagnetic response of bosonic integer quantum Hall (BIQH) phases in odd (space-time) dimensions, and bosonic topological insulator (BTI) and bosonic chiral semimetal (BCSM) phases in even dimensions. To do this, we use the nonlinear sigma model (NLSM) description of bosonic symmetry-protected topological (SPT) phases, and the method of gauged Wess-Zumino (WZ) actions. We find the surprising result that for BIQH states in dimension 2m-1 (m=1,2,»), the bulk response to an electromagnetic field Aμ is characterized by a Chern-Simons term for Aμ with a level quantized in integer multiples of m! (factorial). We also show that BTI states (which have an extra Z2 symmetry) can exhibit a Z2-breaking quantum Hall effect on their boundaries, with this boundary quantum Hall effect described by a Chern-Simons term at level m!2. We show that the factor of m! can be understood by requiring gauge invariance of the exponential of the Chern-Simons term on a general Euclidean manifold, and we also use this argument to characterize the electromagnetic and gravitational responses of fermionic SPT phases with U(1) symmetry in all odd dimensions. We then use our gauged boundary actions for the BIQH and BTI states to (i) construct a bosonic analog of a chiral semimetal (BCSM) in even dimensions, (ii) show that the boundary of the BTI state exhibits a bosonic analog of the parity anomaly of Dirac fermions in odd dimensions, and (iii) study anomaly inflow at domain walls on the boundary of BTI states. In a series of Appendixes we derive important formulas and additional results. In particular, in Appendix A we use the connection between equivariant cohomology and gauged WZ actions to give a mathematical interpretation of the actions for the BIQH and BTI boundaries constructed in this paper. © 2017 American Physical Society.

Date Published

Journal

Physical Review B

Volume

95

Issue

3

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-85012302345&doi=10.1103%2fPhysRevB.95.035149&partnerID=40&md5=fab6e5fb2c50c883dc960fce4825a30c

DOI

10.1103/PhysRevB.95.035149

Group (Lab)

Chao-Ming Jian Group

Funding Source

1125915
1408713
PHY-1125915
N00014-15-1-2383
4304
DMR 1408713

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