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SUMMARY:Ambipolar Property of Isolated Hydrogen in Oxide Materials Reveale
 d by Muon
DTSTART;VALUE=DATE-TIME:20220901T134000Z
DTEND;VALUE=DATE-TIME:20220901T140000Z
DTSTAMP;VALUE=DATE-TIME:20220826T121722Z
UID:indico-contribution-3638@indico.stfc.ac.uk
DESCRIPTION:Speakers: Ryosuke Kadono (IMSS\, KEK)\, Masatoshi Hiraishi (IM
 SS\, KEK)\nThe study on the electronic state of muon as pseudo-hydrogen (r
 epresented by the elemental symbol Mu) by muon spin rotation has long been
  appreciated as one of the few methods to experimentally access the electr
 onic state of dilute hydrogen (H) in semiconductors and dielectrics. Meanw
 hile\, theoretical predictions on the electronic state of H in these mater
 ials by first-principles calculations using density functional theory (DFT
 ) do not always agree with the observed states of Mu.  In order to address
  this long-standing issue\, we have re-examined the vast results of previo
 us Mu studies in insulating/semiconducting oxides with special attention t
 o the non-equilibrium character and the ambipolarity of Mu. As a result\, 
 we established a semi-quantitative model that enables systematic understan
 ding of the electronic states of Mu in most oxides.\nFirst of all\, Mu oft
 en occurs simultaneously in a neutral (Mu$^0$) and a diamagnetic state (Mu
 $^+$ or Mu$^-$) in wide-gap oxides\, which is not explained by DFT calcula
 tions that predict only diamagnetic states with the polarity determined by
  the equilibrium charge-transition level ($E^{+/-}$). Our model considers 
 that $\\mu^+$ interacts with self-induced excitons upon implantation to fo
 rm relaxed-excited states corresponding to a donor-like (Mu$_D$) and/or an
  acceptor-like (Mu$_A$) states. Moreover\, these states are presumed to ac
 company the electronic level ($E^{+/0}$ or $E^{-/0}$) predicted by the DFT
  calculations for H.  By considering that the stability of these two state
 s including their valence is determined by i) the relative position of $E^
 {\\pm/0}$ in the energy band structure of the host and ii) a potential bar
 rier associated with the transition between Mu$_D$ and Mu$_A$\, we find th
 at the known experimental results can be explained systematically in accor
 dance with $E^{\\pm/0}$. The model also provides new insights into the pol
 aron-like nature of the electronic states associated with shallow donor Mu
  complexes and the fast diffusion of Mu$^0_A$.\n\nhttps://indico.stfc.ac.u
 k/event/53/contributions/3638/
LOCATION:Science and Technology Campus\, University of Parma
URL:https://indico.stfc.ac.uk/event/53/contributions/3638/
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