VietNam 2013 

IXth Rencontres du Vietnam
Quy-Nhon, August 4-10, 2013


 Nanophysics: from fundamentals to applications

(the return)


Wednesday 7
Nems, molecules

› 14:00 - 14:20 (20min)
Charge coherence and Fermi-edge singularity in dopant-based devices in silicon
Marc Sanquer  1@  , Benoit Voisin  1@  , Benoit Roche  1@  , Eva Dupont-Ferrier  1@  , Xavier Jehl  1@  , Silvano De Franceschi  1@  , Romain Wacquez  2@  , Maud Vinet  2@  
1 : SPSMS, UMR-E CEA / UJF-Grenoble
INAC, 17 rue des Martyrs, 38054 Grenoble -  France
17 rue des Martyrs, 38054 Grenoble -  France

Single donors in silicon are attracting much attention as qubits [1]. Their sharp confinement potential induces a large valley-orbit splitting [2], which results in a single, spin-degenerate isolated ground-state level used as single-donor spin qubit or two-donor charge qubit. Yet interactions with nearby fluctuating charges can be a source of orbital dephasing. We have measured a charge coherence time T2 of 0.3 ns using LZS interferometry in the first double-donor transistor in silicon [2,3,4]. In such doped devices, these donors strongly couple to ionized donors (charge fluctuators) located at the edges of the reservoirs. Short-range Coulomb interactions between these fluctuating charges and the electrons in the reservoirs can lead to a Fermi edge singularity (FES) [5]. This effect can limit the orbital coherence of coupled donors [6]. To further explore the role of these fluctuating charges, we have measured resonant tunneling transport through donors implanted in a very short silicon nanowire. A current peak is observed when the donor level aligns with the Fermi energy of the reservoir, followed by a power-law decrease of the current, which is in qualitative agreement with the theory of FES [5].
[1] F. Zwanenburg et al., arxiv:1206.5202
[2] B. Roche, et al. PRL. 108, 206812 (2012).
[3] E. Dupont-Ferrier, et al. arXiv:1207.1884v1.
[4] B. Roche, et al. arXiv:1212.1142.
[5] K. A. Matveev and A. I. Larkin, PRB 46, 15337 (1992).
[6] Igor V. Yurkevich, et al. PRB 81,121305 (2010).

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