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Helical Chern insulator phase with broken time-reversal symmetry in MnBi$_2$Te$_4$ | | Chang Liu
; Yongchao Wang
; Ming Yang
; Jiahao Mao
; Hao Li
; Yaoxin Li
; Jiaheng Li
; Haipeng Zhu
; Junfeng Wang
; Liang Li
; Yang Wu
; Yong Xu
; Jinsong Zhang
; Yayu Wang
; | | Date: |
23 Jan 2020 | | Abstract: | A perpetual quest in the field of topological quantum matter is to search for
electronic phases with unprecedented band topology and transport phenomena. The
most prominent example is the discovery of topological insulators, in which
band inversion leads to topologically nontrivial bulk electronic structure and
metallic boundary states. In two-dimensional topological insulators with
time-reversal symmetry, a pair of helical edge states gives rise to the quantum
spin Hall effect. When the time-reversal symmetry is broken by magnetic order,
only one chiral edge mode remains and the quantum anomalous Hall effect emerges
in zero magnetic field. This quantum Hall phase without Landau levels, first
observed in magnetically doped topological insulators, is now called the Chern
insulator. The recently discovered MnBi2Te4 combines intrinsic magnetism and
nontrivial topology in one material, providing an ideal platform for exploring
novel topological phases. Here, we investigate the transport properties of
exfoliated MnBi2Te4 in exceedingly high magnetic fields up to 60 T. By varying
the gate voltage, we observe systematic and yet uniquely complex evolution of
quantized Hall plateaus with Chern numbers from C = -3 to +2. More
surprisingly, a novel phase characterized by an extremely broad zero Hall
plateau emerges as the most robust ground state in the high field limit.
Theoretical calculations reveal that this C = 0 phase arises from the
coexistence of a connate Chern band with C = -1 and a Zeeman-effect-induced
Chern band with C = +1, as corroborated by nonlocal transport measurements.
This helical Chern insulator phase with broken time-reversal symmetry
represents an unexpected new member of the quantum Hall family, and manifests a
new route to change the band topology by using magnetic field. | | Source: | arXiv, 2001.8401 | | Services: | Forum | Review | PDF | Favorites | |
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