Quantum coherent effects in layered nanostructures

Magnetotransport in structures based on NbSe$_3$, Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$, and graphite has been examined. The stimulation of the charge density wave gap by a high magnetic field in NbSe$_3$ has been detected and studied using interlayer tunneling spectroscopy. It has been shown that this stimulation is of orbital character and the effect of the Zeeman splitting of the ground state of the charge density wave on this stimulation has been analyzed. The second harmonic of the gap singularity of the charge density wave in tunneling spectra, which is associated with the cascade relaxation of quasiparticles with the excess energy $2\Delta$. The effects caused by the interaction between Josephson vortices and Abrikosov vortex filaments have been studied on Bi$_2$Sr$_2$СaСu$_2$O$_{8+х}$ mesas. Studies of the magnetoresistance of thin graphite with nanoholes reveal a significant contribution to the magnetotransport from Dirac fermions and provide experimental evidence of the existence of edge states around nanoholes.