Accueil du site > Thèmes de recherche > Physique mésoscopique > En détail > En détail


En détail

 Energy Free Microwave based Signal Communication using Ratchet Effect

E. S. Kannan1*, I. Bisotto1, J.-C. Portal1,2 T. J. Beck3, and L. Jalabert4

 (Nanotechnology 2012 )


 ANR PNANO : MICONANO et NANOTERRA ( 2005-2012 Coordinateur J C Portal ), 


—S. Sassine, Y. Krupko, J.-C. Portal, Z. D. Kvon, R. Murali, K. P. Martin

G. Hill, and A. D. Wieck, Phys. Rev. B 78, 045431 _2008_.

—Bisotto I,Kannan E S,Portal J-C, Murali R, Beck T J and Jalabert L 2011Nanotechnology 22, 24540

—Kannan E S, Bisotto I, Portal J-C, Murali R and Beck T J 2011 Appl. Phys. Lett. 98, 193505

—Bisotto I,Kannan E S,Portal J-C, Murali R, Beck T J and Jalabert L.Nanotechnlogy Highlight July 12 , 2011 ,46501


Transport in disordered two-dimensional topological insulators
Phys. Rev. B 84, 121302(R) (2011) [5 pages
Received 9 June 2011 ; published 9 September 2011
The transport properties of the “inverted” semiconductor HgTe-based quantum well, recently shown to be a two-dimensional topological insulator, are studied experimentally in the diffusive regime.
Nonlocal transport measurements are performed in the absence of magnetic field, and a large signal due to the edge states is observed. This shows that the edge states can propagate over a long distance, 1 mm, and therefore, there is no difference between local and nonlocal electrical measurements in a topological insulator.
 In the presence of an in-plane magnetic field a strong decrease of the local resistance and complete suppression of the nonlocal resistance is observed.
We attribute this behavior to an in-plane magnetic-field-induced transition from the topological insulator state to a conventional bulk metal state.
M. GUSEV et al. PHYSICAL REVIEW B 84, 121302(R) (2011)
(Color online) Schematic top view of the central part of the sample, covered by the gate (shown in blue or light grey)
(a) Red thin lines are edge states localized at the periphery of the sample under a TiAu metallic gate in the TI state. Red areas are the regions with n-type HgTe.

 (b) The diagonal Rxx (thick line, I = 1,6, V = 9,8) and Hall Rxy(dotted line, I = 1,6, V = 9,3) resistances as a function of the gate voltage at zero and fixed magnetic field. The inset shows the temperature dependence of the peak at zero magnetic field. Two traces at zero field are shown in (b) (red solid line, T = 1 K ; blue dashed line, T = 0.08 K)

In summary, we report the observation of a disordered 2D TI state in HgTe quantum wells in zero magnetic field and the emergence of conductive bulk states in the presence of the in-plane magnetic field.

We demonstrate the similarity between local and nonlocal resistance measurements in zero and perpendicular magnetic field in the TI regime. These data offer the evidence that in realistic samples edge-state transport really extends over a macroscopic distance of ∼1 mm in the absence of magnetic field.

Cryogenic systems with 4 Superconducting magnets


Cryogenic systems with Superconducting magnets :
- VTI cryostat (temperature range 1.4–300 K, magnetic field range 0–17 T)
- VTI cryostat (temperature range 2–300 K, magnetic field range 0–12 T)
- 3He system (temperature range 0.3–4.2 K, magnetic field range 0–15 T)
- Dilution fridge (temperature range 30 mK – 1.6 K, magnetic field range 0–17 T)
Cryogenic systems for resistive magnets (up to 34 T) :
VTI cryostat, Continuous Flow Cryostat, 3He system, Dilution fridge
(All systems have large bore diameter 31–37 mm and are equipped with systems of : Top loadings, hydrostatic pressure cells (up to 28 Kbars) : optical and transport, He pressure compressor up to 17 Kbars, optical fibre, rotation of samples, wave guides)
4 electronic units for measurements : Lock-in techniques (ac, dc…), preamplifiers, high impedance measurements…
Set-up for microwave irradiation : Several microwave generators (6 “carcinotrons” with frequency range GHz–0.4 THz and high power (100-150 mW), linear polarization…)
 Modulation and demodulation equipment for any complex information signal