arXiv subjects

T. Tsuneta

Publications and source records attributed to T. Tsuneta.

5 recordsLinked to original sources

arXiv2008

Single-walled carbon nanotube weak links: from Fabry-Pérot to Kondo regime

We have investigated proximity-induced supercurrents in single-walled carbon nanotubes in the Kondo regime and compared them with supercurrents obtained on the same tube with Fabry-Pérot resonances. Our data display a wide distribution of Kondo temperatures \emph{$T_K$} = 1 - 14 K, and the measured critical current $I_{CM}$ vs. \emph{$T_K$} displays two distinct branches; these branches, distinguished by zero-bias splitting of the normal-state Kondo conductance peak, differ by an order of magnitude at large values of $T_K$. Evidence for renormalization of Andreev levels in Kondo regime is also found.

cond-mat.supr-con↗

arXiv2007

Local and Non-local Shot Noise in Multiwalled Carbon Nanotubes

We have investigated shot noise in multiterminal, diffusive multiwalled carbon nanotubes (MWNTs) at 4.2 K over the frequency f = 600 - 850 MHz. Quantitative comparison of our data to semiclassical theory, based on non-equilibrium distribution functions, indicates that a major part of the noise is caused by a non-equilibrium state imposed by the contacts. Our data exhibits non-local shot noise across weakly transmitting contacts while a low-impedance contact eliminates such noise almost fully. We obtain F_{tube}< 0.03 for the intrinsic Fano factor of our MWNTs.

cond-mat.mes-hall↗

arXiv2007

Shot Noise with Interaction Effects in Single Walled Carbon Nanotubes

We have measured shot noise in single walled carbon nanotubes (SWNT) with good contacts at 4.2 K at low frequencies ($f=600 - 850$ MHz). We find a strong modulation of shot noise over the Fabry-Perot pattern; in terms of differential Fano factor the variation ranges over 0.4 - 1.2. The shot noise variation, in combination with differential conductance, is analyzed using two (spin-degenerate) modes with different, energy-dependent transmission coefficients. No power law dependence of shot noise, as expected for Luttinger liquids, was found in our measurements.

cond-mat.mes-hall↗

arXiv2006

Gate-controlled superconductivity in diffusive multiwalled carbon nanotube

We have investigated electrical transport in a diffusive multiwalled carbon nanotube contacted using superconducting leads made of Al/Ti sandwich structure. We find proximity-induced superconductivity with measured critical currents up to I_cm = 1.3 nA, tunable by gate voltage down to 10 pA. The supercurrent branch displays a finite zero bias resistance which varies as R_0 proportional to I_cm^-alpha with alpha=0.74. Using IV-characteristics of junctions with phase diffusion, a good agreement is obtained with Josephson coupling energy in the long, diffusive junction model of A.D Zaikin and G.F. Zharkov (Sov. J. Low Temp. Phys. 7, 184 (1981)).

cond-mat.supr-con↗

arXiv2006

Shot noise of a multiwalled carbon nanotube field effect transistor

We have investigated shot noise in a 6-nm-diameter, semiconducting multiwalled carbon nanotube FET at 4.2 K over the frequency range 600 - 950 MHz. We find a transconductance of 3 - 3.5 $μ$S for optimal positive and negative source-drain voltages V. For the gate referred input voltage noise, we obtain 0.2 and 0.3 $μ{V}/ \sqrt{Hz}$ for V>0 and V<0, respectively. As effective charge noise this corresponds to $2-3 \cdot 10^{-5}$ e/$\sqrt{Hz}$.

cond-mat.mes-hall↗