Papers by Laurent Saminadayar
Physical Review B
We have measured the resistivity of magnetically doped Ag:Mn mesoscopic wires as a function of te... more We have measured the resistivity of magnetically doped Ag:Mn mesoscopic wires as a function of temperature and magnetic field. The doping has been made using ion implantation, allowing a distribution of the dopants in the middle of the sample. Comparison with an undoped sample, used as a reference sample, shows that the resistivity of the doped sample exhibits nonmonotonic behavior as a function of both magnetic field and temperature, revealing the competition between the Kondo effect and the RKKY interactions between spins. This proves that transport measurements are still a reliable probe of the spin-glass transition in nanoscopic metallic wire doped using implantation.
Eprint Arxiv Cond Mat 0407200, Jul 8, 2004
We report on magnetotransport measurements performed on a large metallic two-dimensional T3 netwo... more We report on magnetotransport measurements performed on a large metallic two-dimensional T3 network. Superimposed on the conventional Altshuler-Aronov-Spivak (AAS) oscillations of period h/2e, we observe clear h/e oscillations in magnetic fields up to 8 T. Different interpretations of this phenomenon are proposed.
International Journal of Nanotechnology, 2010
ABSTRACT The time τ φ over which an electron can maintain its phase coherence at low temperatures... more ABSTRACT The time τ φ over which an electron can maintain its phase coherence at low temperatures is of fundamental importance in mesoscopic systems. The observability of many phenomena, such as the Aharonov Bohm effect, the universal conductance fluctuations, the weak localisation correction to the conductance, persistent current in ringstructures and many more rely on a long enough phase coherence time. In disordered conductors and within the standard Fermi liquid picture, the phase coherence time is expected to diverge at zero temperature. However, most experiments show a saturating phase coherence time at low temperatures. This saturation has often been attributed to the presence of a small amount of magnetic impurities giving rise to the so-called Kondo effect. In this paper, we present a brief review of recent advances, both experimental and theoretical, in the understanding of dephasing by magnetic impurities in the framework of the Kondo effect. they have founded a research group devoted to the study of quantum (spin) transport in nanoscale devices at the Néel Institute, Grenoble, France. Their work concerns quantum coherence in Kondo systems and spin glasses, Kondo effect in semiconductor nanostructures and more recently spin based quantum bits and nanomechanics. The group has good expertise in very low temperature physics under high magnetic field, ultra-low noise transport measurements and micro-SQUID magnetometry. 2 C. Bäuerle et al. Pascal Degiovanni is CNRS researcher at the École Normale Supérieure of Lyon, in the condensed matter theory group. He has worked in decoherence problems in superconducting qubits, cavity QED and Luttinger liquids. He is now working on the development of quantum optics formalism for electrons. His expertise includes field theory methods in condensed matter physics as well as dissipative quantum dynamics.
Physica B, 1998
The existence of fractional charges carrying the current is experimentally demonstrated. Using a ... more The existence of fractional charges carrying the current is experimentally demonstrated. Using a 2-D electron system in high perpendicular magnetic field we measure the shot noise associated with tunneling in the fractional quantum Hall regime at Landau level filling factor. The noise gives a direct determination of the quasiparticle charge, which is found to be e * "e/3 as predicted by Laughlin. The existence of e/3 Laughlin quasiparticles is unambiguously confirmed by the shot noise to Johnson-Nyquist cross-over found for temperature "e * » BQ /2k .
Physica B, 1996
We present a comprehensive experimental study of mesoscopic noise in a GaAs quantum point contact... more We present a comprehensive experimental study of mesoscopic noise in a GaAs quantum point contact. In agreement with existing theory, we find that the measured noise power is strongly reduced from the full shot noise 2eI (I is the time-averaged current) expected for completely uncorrelated electron transport. Study of the temperature dependence of the noise clearly demonstrates the transition from
Phys Rev Lett, 1996
... 8 APRIL 1996 Experimental Test of the Quantum Shot Noise Reduction Theory A. Kumar, L. Samina... more ... 8 APRIL 1996 Experimental Test of the Quantum Shot Noise Reduction Theory A. Kumar, L. Saminadayar, and ... below 200 mK the thermalization length of electrons with phonons is largerthan the sample ... We thank P. Jacques for valuable technical help, P. Pari and P. Forget for ...
Toward the Controllable Quantum States, 2003
ABSTRACT We present measurements of the magnetic response of a network of connected mesoscopic Ga... more ABSTRACT We present measurements of the magnetic response of a network of connected mesoscopic GaAs/GaAlAs rings whose total size is much larger than the phase coherence length. We observe a clear magnetic response with a flux periodicity of h/e. Direct comparison with measurements on the same sample with isolated rings shows that the persistent current is only weakly affected by the connection of the rings.
Reflets de la physique, 2014
physica status solidi (a), 2010
… of Nanoscience and …, 2004
Diamond is an electrical insulator in its natural form. However, when doped with boron above a cr... more Diamond is an electrical insulator in its natural form. However, when doped with boron above a critical level (∼ 0.25 at.%) it can be rendered superconducting at low temperatures with high critical fields. Here we present the realization of a micrometer scale superconducting quantum interference device (µ-SQUID) made from nanocrystalline boron doped diamond (BDD) films. Our results demonstrate that µ-SQUIDs made from superconducting diamond can be operated in magnetic fields as large as 4T independent on the field direction. This is a decisive step towards the detection of quantum motion in a diamond based nanomechanical oscillator.
International Journal of Nanoscience, 2003
ABSTRACT We present calculations of the quantum oscillations appearing in the transmission of a m... more ABSTRACT We present calculations of the quantum oscillations appearing in the transmission of a mesoscopic GaAs/GaAlAs ring isolated by quantum point contacts. We show that the device acts as an electronic Fabry–Perot spectrometer in the quantum Hall effect regime, and discuss the effect of the coherence length of edge states.
We report on magnetoconductance measurements of metallic networks of various sizes ranging from 1... more We report on magnetoconductance measurements of metallic networks of various sizes ranging from 10 to 10 6 plaquettes, with an anisotropic aspect ratio. Both Altshuler-Aronov-Spivak h=2e periodic oscillations and Aharonov-Bohm h=e periodic oscillations are observed for all networks. For large samples, the amplitude of both oscillations results from the incoherent superposition of contributions of phase coherent regions. When the transverse size becomes smaller than the phase coherent length L , one enters a new regime which is phase coherent (mesoscopic) along one direction and macroscopic along the other, leading to a new size dependence of the quantum oscillations.
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Papers by Laurent Saminadayar