Anderson–Mott transition in arrays of a few dopant atoms in a silicon transistor
Laboratorio MDM, IMM-CNR, Via Olivetti 2, Agrate Brianza, Italy. Nature Nanotechnology
(Impact Factor: 34.05).
07/2012; 7(7):443-7. DOI: 10.1038/nnano.2012.94
Dopant atoms are used to control the properties of semiconductors in most electronic devices. Recent advances such as single-ion implantation have allowed the precise positioning of single dopants in semiconductors as well as the fabrication of single-atom transistors, representing steps forward in the realization of quantum circuits. However, the interactions between dopant atoms have only been studied in systems containing large numbers of dopants, so it has not been possible to explore fundamental phenomena such as the Anderson-Mott transition between conduction by sequential tunnelling through isolated dopant atoms, and conduction through thermally activated impurity Hubbard bands. Here, we observe the Anderson-Mott transition at low temperatures in silicon transistors containing arrays of two, four or six arsenic dopant atoms that have been deterministically implanted along the channel of the device. The transition is induced by controlling the spacing between dopant atoms. Furthermore, at the critical density between tunnelling and band transport regimes, we are able to change the phase of the electron system from a frozen Wigner-like phase to a Fermi glass by increasing the temperature. Our results open up new approaches for the investigation of coherent transport, band engineering and strongly correlated systems in condensed-matter physics.
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- "The possibilities opened by nanofabrication of semiconductor devices   have been exploited by engineering the ability to control the position of impurity atoms at nanometric precision by a one-by-one method of implantation called single ion implantation (SII). Taking advantage of this method, developed in the last decade by three groups in the world   , it has been possible to create chains of individually implanted ions in silicon , and to investigate the effects caused by their proximity and the residual disorder affecting their position and ground state energy distribution . Therefore, the transition from a single particle behaviour to collective phenomena is directly observed. "
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ABSTRACT: The advancements of nanofabrication, together with the control of
implantation of individual atoms at nanometric precision, have opened
the experimental study of phase transitions of electronic systems
constituted by six electrons and less. Here I review the recent
advancements made in the field of phase transitions at the few atoms
scale, including the discretized version of the Anderson-Mott quantum
phase transition and the melting of electrons arranged in a Wigner-like
phase into a Fermi glass realized in a Si : X quantum device where X is
a donor element. The rise of collective phenomena is directly probed by
controlling the distance between few donor atoms. Four atoms are
sufficient to observe emergent phenomena such as Hubbard bands instead
of single particle behaviour.
Journal of Physics Conference Series 06/2013; 442(1):2023-. DOI:10.1088/1742-6596/442/1/012023
Available from: Ren-Bao Liu
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ABSTRACT: Quantum criticality occurs when the ground state of a macroscopic quantum system changes abruptly on tuning system parameters. It is an important indicator of new quantum matters emerging. In conventional methods, quantum criticality is observable only at zero or low temperature (as compared with the interaction strength in the system). We find that a quantum probe, if its coherence time is long, can detect the quantum criticality of a system at high temperature. In particular, the echo control over a spin probe can remove the thermal fluctuation effects and hence reveal the critical quantum fluctuation without requiring low temperature. We first use the exact solution of the one-dimensional transverse-field Ising model to demonstrate the possibility of detecting the quantum criticality at high temperature by spin echo. The critical behaviors were calculated using the exact solution and understood by the noise spectrum analysis in the Gaussian noise approximation. By numerical simulation, we further verify that the high-temperature quantum criticality also exists in the probe coherence measurement of spin systems with dipolar couplings. Using the noise spectrum analysis, we establish the correspondence between the necessary low temperature (TQC) in conventional methods and the necessary long coherence time (tQC) in probe decoherence measurement to observe the quantum criticality, that is, TQC ~ 1/tQC and much less than the interaction strength of the system. For example, probes with quantum coherence times of milliseconds or seconds can be used to study, without cooling the system, quantum criticality that was previously known to be only observable at extremely low temperatures of nano- or pico-kelvin. This finding provides a new possibility to study quantum matters.
New Journal of Physics 04/2013; 15(4):043032. DOI:10.1088/1367-2630/15/4/043032 · 3.56 Impact Factor
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ABSTRACT: The integration of atomic physics with quantum device technology contributed to the exploration of the field of single electron nanoelectronics originally developed in single electron quantum dots. Here the basic concepts of single electron nanoelectronics, including key aspects of architectures, quantum transport in silicon devices, single electron transistors, few atom devices, single charge/spin dynamics, and the role of valleys and bands are reviewed. Future applications in fundamental physics and classical and quantum information technologies are discussed, by highlighting the critical aspects which currently impose limits to the most advanced developments at the 10-nm node.
Journal of Nanoparticle Research 05/2013; 15(5). DOI:10.1007/s11051-013-1615-4 · 2.18 Impact Factor
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