Observation of coherent modes of Josephson vortices in Bi2Sr2CaCu2Ox

Abstract

We report strong evidence for coherent modes of moving Josephson vortices in mesas patterned on the surface of Bi2Sr2CaCu2Ox single crystals. The vortex flow current–voltage curves are characterized by a sharp up-turn and the appearance of multiple branches as the current is ramped up and down at a fixed magnetic field and temperature. These results are consistent with weakly damped motion of Josephson vortices in which different coherent modes can occur in a close stack of Josephson coupled multilayers.

Collective Josephson vortex dynamics in long Josephson junction stacks

“…7,8,9 Note that these supercurrent sub-branches differ from the observed multiple quasiparticle branches 12,19,13 in the I-V data for LJJ stacks.…”

“…(28) To observe these branches, a magnetic field, stronger than B ∼ H o , may be needed because of their stability conditions. Note that the appearance of these high velocity branches is expected when the interaction between the vortices is increased by the field, 8 suggesting that a complete sub-branch structure may be more easily obtained from the I-V characteristics of a LJJ stack with increasing microwave irradiation power (i.e., AC magnetic fields). 9 These results are consistent with the data 7,8,9 exhibiting supercurrent branch splitting.…”

“…7,8,9 The experiments on both conventional LJJ stacks 7 (e.g., Nb-Al/AlO x -Nb multilayers) and layered superconductors 5,6,8,9 (e.g., Bi 2 Sr 2 CaCu 2 O 8+y (BSCCO)) behaving as intrinsic LJJ stacks 10 indicate that JPR can be tuned 11 by magnetic field B and can occur over a broad range of frequencies, from microwave to submillimeter-wave. Also, the supercurrent branch in the current-voltage (I-V) data splits into multiple sub-branches when a bias current exceeds some critical value.…”

“…Also, the supercurrent branch in the current-voltage (I-V) data splits into multiple sub-branches when a bias current exceeds some critical value. 8 To explain the data, 5,6,7,8,9 two theoretical models have been proposed:…”

Josephson-Vortex-Flow Terahertz Emission in Layered High-TcSuperconducting Single Crystals

“…In a higher magnetic field of H=3.9 T as in the region (ii) of the main panel of Fig. 2, however, the single vortexflow branch splits into multiple vortex-flow sub-branches, which arise as a result of phase-locking of a Josephson vortex lattice on multiple SJP modes [14,15]. SJP oscillations in each mode, standing along the c axis, propagate along junctions with a characteristic collective mode velocity [7,8], c n = c 0 / 1 − cos[πn/(N + 1)].…”