Josephson vortices in naturally stacked Bi2Sr2CaCu2O 8+δ tunneling junctions display rich dynamic behavior that derives from the coexistence of three basic states: static Josephson vortex lattice, coherently moving lattice, and incoherent quasiparticle tunneling state. Rich structure of hysteretic branches observed in the current-voltage characteristics can be understood as combinatorial combinations of these three states which are realized in different junctions and evolve separately with magnetic field and bias current. In particular, the multiple Josephson-vortex-flow branches at low bias currents arise from the individual depinning of Josephson vortex rows in each junction.Natural Josephson junctions (JJs), closely packed in an atomic scale, form along the c axis of highly anisotropic Bi 2 Sr 2 CaCuO 8+δ (Bi-2212) superconductors [1]. Josephson vortices (JVs) are generated in these naturally stacked JJs in an in-plane magnetic field. Since the period between adjacent CuO 2 bilayers, s (=1.5 nm), is much smaller than the in-plane component of the London penetration depth λ ab (∼ 200 nm), a Josephson vortex (JV) spreads over many junctions, which leads to inductive coupling between JVs. In stacked JJs, JVs fill every junction in a field higher than B cr = Φ 0 /(2πγs 2 ) (∼0.75 T for Bi-2212), where γ (≡ λ c /λ ab ∼250; λ c is the out-of-plane penetration depth) is the magnetic anisotropy ratio. In this high-field region, JVs configurations in the static state are well understood and are known to be in a triangular lattice [2,3,4,5]. Despite much interest, however, dynamic state of JVs is far less understood although various aspects of dynamical properties are proposed including the possible lattice structures [6,7,8], interaction between JVs and electromagnetic excitations [9,10,11,12], and coherent characters of the JV motion [13] over the whole junctions in a stack.Key elements governing the dynamics of JVs are well reflected in the tunneling current-voltage (I-V) characteristics, which reveal the relation between the driving force acting on JVs in a junction by the bias current and the responsive JVs motion that induces a voltage drop across the junctions. For instance, JV viscosity is determined by the in-and out-of-plane quasiparticle dissipation that is extracted from the tunneling JV-flow resistance [14,15]. Oscillatory tunneling magnetoresistance is also used to confirm the coherently moving JV lattice and the influence of the edge barrier potential on * Corresponding author: hjlee@postech.ac.kr the JV motion [16,17,18]. Interaction between JVs and electromagnetic excitations is another interesting subject of JV dynamics where the resonance with cavity modes appears as Fiske steps [12,19]. Moreover, resonance between collectively moving JVs and plasma mode excitations in naturally stacked JJs has been studied extensively [9,10,11] where multiple subbranches in the I-V characteristics have been claimed to be an experimental evidence for the resonance [8]. The interaction between Josephson and pancake vo...

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We investigated the thermal-depinning current ͑I c ͒ distribution of Josephson vortices ͑JVs͒ in naturally stacked Bi 2 Sr 2 CaCu 2 O 8+␦ intrinsic Jospehson junctions in tesla-range magnetic fields and at different field tilt angles from the in-plane position. The I c distribution in the thermal-activation regime contains accurate information on the bias and magnetic-field dependence of the Josephson-vortex pinning potential. In a few-teslarange magnetic field, JVs in a row in a junction, strongly coupled with each other, are pinned or depinned like a single physical entity at a single pinning center. In the best-aligned in-plane magnetic field, the edge pinning is most relevant and is insensitive to the field strength. In the presence of pancake vortices ͑PVs͒ in a slightly tilted field, however, the PV pinning deepens the JV pinning potential linearly with the number of PVs.