1. Students: Alexei Zubarev *and Camelia Sold** *Faculty of Physics, University of Bucharest **Faculty of Physics, West University of Timisoara Coordinators***: D. Kolesnikov, V. Katkov ***Bogoliubov Laboratory of Theoretical Physics, JINR, Dubna

2. Carbon nanostructures Graphene Nanotubes Graphene pillars

3. Nanotubes properties Nanotubes have a very broad range of electonic, thermal, and structural properties that change depending on the different kinds of nanotube (defined by its diameter, length, and chirality, or twist). To make things more interesting, besides having a single cylindrical wall (SWNTs), nanotubes can have multiple walls (MWNTs)--cylinders inside the other cylinders. Currently, the physical properties are still being discovered and disputed.

4. Electrons in nanotubes The behavior of electrons is descibed by the Dirac equation:

5. Nanotubes under magnetic field Magnetic flux: Dirac equations for Ψ T =(Ψ 1,Ψ 2 ) have the following form:

6. Magnetic barrier

7. Rotational deformation α Rotational deformation is equivalent to magnetic field

8. Results Transmission in function of rotational deformation: T(α) L=10, 5, 2, 1 Metallic channel Secondary channel m = 0 L = 0.05, 0.5, 1, 2 m = 1

9. Results E = 0.01, 0.5, 0.7, 1 The transmission dependence on deformation for different energies Transmission value doesn’t depend significantly on energy The transmission dependence on deformation if we rotate only the centre of the nanotube The secondary channels don’t influence significantly the value of transmission m = 0 m = -1 m = 1

10. Conclusions Transmission doesn’t depend significantly on energy Transmission decreases when the nanotube length increases For the main channel, transmission decreases sharply when deformation (magnetic field) increases For the main channel, transmission depends only on the total deformation For the secondary channel (electrons with positive m), transmission decreases when deformation increases

11. Possible applications Using nanotubes we can assemble an electronical device that works based on magnetic field. The signal decreases sharply when magnetic field is applied. The results we obtained can be applied to make a sensor similar to Coulomb Balance. The value of force can be measured by the current variation.