TY - JOUR

T1 - Half quantum spin Hall effect on the surface of weak topological insulators

AU - Liu, Chao Xing

AU - Qi, Xiao Liang

AU - Zhang, Shou Cheng

N1 - Funding Information:
We would like to thank Yaacov E. Kraus, G. Li and B. Trauzettel for helpful discussions. SCZ is supported by the NSF under grant numbers DMR-0904264 and the Keck Foundation. XLQ is supported by the Alfred P. Sloan Foundation. CXL acknowledge financial support by the Alexander von Humboldt Foundation of Germany. CXL is grateful for the hospitality of the Institute for Advanced Study in Tsinghua University. All the authors also thank the hospitality of KITP in UCSB.

PY - 2012/2

Y1 - 2012/2

N2 - We investigate interaction effects in three dimensional weak topological insulators (TI) with an even number of Dirac cones on the surface. We find that the surface states can be gapped by a surface charge density wave (CDW) order without breaking the time-reversal symmetry. In this sense, time-reversal symmetry alone cannot robustly protect the weak TI state in the presence of interactions. If the translational symmetry is additionally imposed in the bulk, a topologically non-trivial weak TI state can be obtained with helical edge states on the CDW domain walls. In other words, a CDW domain wall on the surface is topologically equivalent to the edge of a two-dimensional quantum spin Hall insulator. Therefore, the surface state of a weak topological insulator with translation symmetry breaking on the surface has a half quantum spin Hall effect, in the same way that the surface state of a strong topological insulator with time-reversal symmetry breaking on the surface has a half quantum Hall effect. The on-site and nearest neighbor interactions are investigated in the mean field level and the phase diagram for the surface states of weak topological insulators is obtained.

AB - We investigate interaction effects in three dimensional weak topological insulators (TI) with an even number of Dirac cones on the surface. We find that the surface states can be gapped by a surface charge density wave (CDW) order without breaking the time-reversal symmetry. In this sense, time-reversal symmetry alone cannot robustly protect the weak TI state in the presence of interactions. If the translational symmetry is additionally imposed in the bulk, a topologically non-trivial weak TI state can be obtained with helical edge states on the CDW domain walls. In other words, a CDW domain wall on the surface is topologically equivalent to the edge of a two-dimensional quantum spin Hall insulator. Therefore, the surface state of a weak topological insulator with translation symmetry breaking on the surface has a half quantum spin Hall effect, in the same way that the surface state of a strong topological insulator with time-reversal symmetry breaking on the surface has a half quantum Hall effect. The on-site and nearest neighbor interactions are investigated in the mean field level and the phase diagram for the surface states of weak topological insulators is obtained.

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U2 - 10.1016/j.physe.2011.11.005

DO - 10.1016/j.physe.2011.11.005

M3 - Article

AN - SCOPUS:84859216375

VL - 44

SP - 906

EP - 911

JO - Physica E: Low-Dimensional Systems and Nanostructures

JF - Physica E: Low-Dimensional Systems and Nanostructures

SN - 1386-9477

IS - 5

ER -