Collective responses of Bi-2212 stacked junction to 100 GHz microwave radiation under magnetic field oriented along the c-axis

We studied a response of Bi-2212 mesa type structures to 100 GHz microwave radiation. We found that applying magnetic field of about 0.1 T across the layers enables to observe collective Shapiro step response corresponding to a synchronization of all 50 intrinsic Josephson junctions (IJJ) of the mesa. At high microwave power we observed up to 10th harmonics of the fundamental Shapiro step. Besides, we found microwave induced flux-flow step position of which is proportional to the square root of microwave power and that can exceed at high enough powers 1 THz operating frequency of IJJ oscillations.Comment: 11 pages including 5 figures, accepted for publication in JETP Letter

Anomalous asymmetry of magnetoresistance in NbSe3_3 single crystals

A pronounced asymmetry of magnetoresistance with respect to the magnetic field direction is observed for NbSe$_3$ crystals placed in a magnetic field perpendicular to their conducting planes. It is shown that the effect persists in a wide temperature range and manifests itself starting from a certain magnetic induction value $B_0$, which at $T=4.2$ K corresponds to the transition to the quantum limit, i.to the state where the Landay level splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let

Interlayer tunneling spectroscopy of graphite at high magnetic field oriented parallel to the layers

Interlayer tunneling in graphite mesa-type structures is studied at a strong in-plane magnetic field $H$ up to 55 T and low temperature $T=1.4$ K. The tunneling spectrum $dI/dV$ vs. $V$ has a pronounced peak at a finite voltage $V_0$. The peak position $V_0$ increases linearly with $H$. To explain the experiment, we develop a theoretical model of graphite in the crossed electric $E$ and magnetic $H$ fields. When the fields satisfy the resonant condition $E=vH$, where $v$ is the velocity of the two-dimensional Dirac electrons in graphene, the wave functions delocalize and give rise to the peak in the tunneling spectrum observed in the experiment.Comment: 6 pages, 6 figures; corresponds to the published version in Eur. Phys. J. Special Topics, Proceedings of the IMPACT conference 2012, http://lptms.u-psud.fr/impact2012

Nanopattern-stimulated superconductor-insulator transition in thin TiN films

We present the results of the comparative study of the influence of disorder on transport properties in continuous and nanoperforated TiN films. We show that nanopatterning turns a thin TiN film into an array of superconducting weak links and stimulates both, the disorder- and magnetic field-driven superconductor-to-insulator transitions, pushing them to lower degree of disorder. We find that nanopatterning enhances the role of the two-dimensional Coulomb interaction in the system transforming the originally insulating film into a more pronounced insulator. We observe magnetoresistance oscillations reflecting collective behaviour of the multiconnected nanopatterned superconducting film in the wide range of temperatures and uncover the physical mechanism of these oscillations as phase slips in superconducting weak link network.Comment: 6 pages, 4 figure

High-frequency oscillations in low-dimensional conductors and semiconductor superlattices induced by current in stack direction

A narrow energy band of the electronic spectrum in some direction in low-dimensional crystals may lead to a negative differential conductance and N-shaped I-V curve that results in an instability of the uniform stationary state. A well-known stable solution for such a system is a state with electric field domain. We have found a uniform stable solution in the region of negative differential conductance. This solution describes uniform high-frequency voltage oscillations. Frequency of the oscillation is determined by antenna properties of the system. The results are applicable also to semiconductor superlattices.Comment: 8 pages, 3 figure

Experimental Evidence for Coulomb Charging Effects in the Submicron Bi-2212 Stacks

We developed the focused ion beam (FIB) and ion milling techniques for a fabrication of the Bi_2Sr_2CaCu_2O_{8+\delta} (Bi-2212) stacked junctions with in-plane size L_{ab} from several microns down to the submicron scale without degradation of T_c. We found that behaviour of submicron junctions (L_{ab} < 1 {\mu}m) is quite different from the bigger ones. The critical current density is considerably suppressed, the hysteresis and multibranched structure of the IV characteristics are eliminated, the periodic structure of current peaks reproducibly appears on the IV curves at low temperatures. A period of the structure, {\Delta}V, is consistent with the Coulomb charging energy of a single pair, {\Delta}V = e/C with C the effective capacitance of the stack. We consider this behaviour to originate from the Coulomb blockade of the intrinsic Josephson tunneling in submicron Bi-2212 stacks.Comment: 13 pp, incl. 1 table and 4 fig