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23 April 2024 |
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Observation of pseudospin Berry phase as a signature of nontrivial band topology in a coupled electron-hole system | | F. Couëdo
; H. Irie
; T. Akiho
; K. Suzuki
; K. Onomitsu
; K. Muraki
; | | Date: |
14 Feb 2019 | | Abstract: | Electron motion in crystals is governed by the coupling between crystal
momentum and internal degrees of freedom such as spin implicit in the band
structure. The description of this coupling in terms of a momentum-dependent
effective field and the resultant Berry phase has renovated the understanding
of diverse phenomena including various Hall effects, which underlies the
discovery of new states of matter exemplified by topological insulators. While
experimental studies on topological systems have focused on the gapless states
that emerge at the surfaces or edges, the underlying nontrivial topology in the
bulk has not been manifested. Here we report the observation of Berry’s phase
in magneto-oscillations and quantum Hall effects of a coupled electron-hole
system hosted in quantum wells with inverted bands. In contrast to massless
Dirac fermions in graphene, for which Berry’s phase $Gamma$ is quantized at
$pi$, we observe that $Gamma$ varies with the Fermi level $E_mathrm{F}$,
passing through $pi$ as $E_mathrm{F}$ traverses the energy gap that opens due
to electron-hole hybridization. We show that the evolution of $Gamma$ is a
manifestation of the pseudospin texture that encodes the momentum-dependent
electron-hole coupling and is therefore a signature of the nontrivial band
topology. Our results suggest a way to engineering Berry curvature exploiting
the bulk states, which may provide new functionalities in spintronics
applications. | | Source: | arXiv, 1902.5310 | | Services: | Forum | Review | PDF | Favorites | |
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