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VOLUME 108 (2018) | ISSUE 10 |
PAGE 700
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Noise in the helical edge channel anisotropically coupled to a local spin
K. E. Nagaev+, S. V. Remizov+*, D. S. Shapiro+*
+Kotelnikov Institute of Radioengineering and Electronics, 125009 Moscow, Russia *Dukhov Research Institute of Automatics (VNIIA), 127055 Moscow, Russia
Abstract
We calculate the frequency-dependent shot noise in the edge states of a
two-dimensional topological insulator coupled to
a magnetic impurity with spin S=1/2 of arbitrary anisotropy. If the
anisotropy is absent, the noise is purely thermal
at low frequencies,
but tends to the Poissonian noise of the full current I at high
frequencies. If the interaction only flips the impurity spin
but conserves those of electrons, the noise at high voltages is
frequency-independent. Both the noise and the backscattering
current Ibs saturate at voltage-independent values. Finally, if the
Hamiltonian
contains all types of non-spin-conserving scattering, the noise at high
voltages becomes frequency-dependent again. At low
frequencies, its ratio to 2eIbs is larger than 1 and may reach 2 in
the limit Ibs→ 0. At high frequencies it tends
to 1.
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