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@ARTICLE{Placke:842890,
      author       = {Placke, B. and Bosco, S. and DiVincenzo, David},
      title        = {{A} model study of present-day {H}all-effect circulators},
      journal      = {EPJ Quantum Technology},
      volume       = {4},
      number       = {1},
      issn         = {2196-0763},
      address      = {Berlin},
      publisher    = {Springer Open},
      reportid     = {FZJ-2018-01063},
      pages        = {5},
      year         = {2017},
      abstract     = {Stimulated by the recent implementation of a three-port
                      Hall-effect microwave circulator of Mahoney et al. (MEA), we
                      present model studies of the performance of this device. Our
                      calculations are based on the capacitive-coupling model of
                      Viola and DiVincenzo (VD). Based on conductance data from a
                      typical Hall-bar device obtained from a two-dimensional
                      electron gas (2DEG) in a magnetic field, we numerically
                      solve the coupled field-circuit equations to calculate the
                      expected performance of the circulator, as determined by the
                      $S$ parameters of the device when coupled to 50$\Omega$
                      ports, as a function of frequency and magnetic field. Above
                      magnetic fields of 1.5T, for which a typical 2DEG enters the
                      quantum Hall regime (corresponding to a Landau-level filling
                      fraction $\nu$ of 20), the Hall angle
                      $\theta_H=\tan^{-1}\sigma_{xy}/\sigma_{xx}$ always remains
                      close to $90^\circ$, and the $S$ parameters are close to the
                      analytic predictions of VD for $\theta_H=\pi/2$. As
                      anticipated by VD, MEA find the device to have rather high
                      (k$\Omega$) impedance, and thus to be extremely mismatched
                      to $50\Omega$, requiring the use of impedance matching. We
                      incorporate the lumped matching circuits of MEA in our
                      modeling and confirm that they can produce excellent
                      circulation, although confined to a very small bandwidth. We
                      predict that this bandwidth is significantly improved by
                      working at lower magnetic field when the Landau index is
                      high, e.g. $\nu=20$, and the impedance mismatch is
                      correspondingly less extreme. Our modeling also confirms the
                      observation of MEA that parasitic port-to-port capacitance
                      can produce very interesting countercirculation effects.},
      cin          = {PGI-2},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-2-20110106},
      pnm          = {144 - Controlling Collective States (POF3-144)},
      pid          = {G:(DE-HGF)POF3-144},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {1609.09624},
      howpublished = {arXiv:1609.09624},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:1609.09624;\%\%$},
      UT           = {WOS:000407196900001},
      doi          = {10.1140/epjqt/s40507-017-0057-9},
      url          = {https://juser.fz-juelich.de/record/842890},
}