Magnetic Field Evolution of the Linear and Nonlinear Conduction of Perforated TiN Films
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DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Magnetic Field Evolution of the Linear and Nonlinear Conduction of Perforated TiN Films A. Yu. Mironova,b,*, S. V. Postolovaa, and D. A. Nasimova a Institute
of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630090 Russia b Novosibirsk State University, Novosibirsk, 630090 Russia *e-mail: [email protected] Received December 11, 2019; revised January 14, 2020; accepted January 30, 2020
Abstract—The low-temperature linear and nonlinear transport on nanoperforated titanium nitride films is experimentally studied. A metallic Bose state is shown to appear in the system, and it transforms into a metallic state in a magnetic field. The linear and differential magnetoresistances of the system exhibit oscillations. A vortex Mott insulator was shown to transfer into a metallic state when a direct current passes through a film. DOI: 10.1134/S1063776120050167
1. INTRODUCTION The electrical resistance of a nanostructured system, such as a regular array of superconducting islands on a non-superconducting substrate or a regular array of holes in a superconducting film, as a function of magnetic field B is known to exhibit oscillations with period B0, which corresponds to magnetic flux quantum h/2e per cell area [1–5]. The authors of [6] found that the passage of a direct current through a twodimensional network of Josephson junctions radically changed the oscillations of differential magnetoresistance dV/dI(f): minima at a fractional number of magnetic flux quanta per cell f = B/B0 were replaced by maxima when a certain threshold current was reached, which corresponded to the oscillation behavior of the critical current in a magnetic field. Analogous behavior of dV/dI(f) was recently observed in a square array of superconducting Nb islands on a gold substrate [7, 8]. The authors of those works showed that minima changed into maxima when the current changes at both fractional and integral numbers f. They related this behavior to a dynamic transition of a vortex lattice from the state of a vortex Mott insulator to a metallic state, i.e., the state of vortex liquid. As was shown in [9], the type of differential resistance dV/dI in a vortex Mott insulator indicates the density of vortex states; that is, the dip at I = 0 changes into a peak during the transition into a metallic state when I increases. Similarly, the density of electronic states in an electronic Mott insulator is determined from differential conductivity dI/dV [10], and the density of states in the insulating state has a dip at V = 0, which changes into a peak during the transition into a metallic state when V increases.
2. EXPERIMENTAL We experimentally studied the linear and nonlinear magnetic transport in nanostructured superconducting disordered films. As a base material, we used a 5-nm-thick superconducting TiN film grown upon atomic-layer deposition at a temperature of 350°C. Interest in titanium nitride films is caused by the presence of a superconductor–insulator phase tr
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