Josephson plasma resonance inκ−(BEDT−TTF)2Cu(NCS

Abstract

A cavity perturbation technique is used to study the microwave response of the organic superconductor -(BEDT-TTF) 2 Cu(NCS) 2 . Observation of a Josephson plasma resonance, below T c (ϳ10 K), enables investigation of the vortex structure within the mixed state of this highly anisotropic, type-II superconductor. Contrary to previous assumptions, frequency-dependent studies ͑28-153 GHz͒ indicate that the squared plasma frequency ( p 2 ) depends exponentially on the magnetic-field strength. Such behavior has been predicted for a weakly pinned quasi-two-dimensional vortex lattice ͓Bulaevskii et al., Phys. Rev. Lett. 74, 801 ͑1995͔͒. Our data also suggests a transition in the vortex structure near the irreversibility line.

Temperature dependence of the Josephson plasma resonance between vortex phases in the organic superconductor κ-(BEDT-TTF)2Cu(NCS)2

“…weak disorder [11]. Previous studies focused on the field dependence of u p across the boundary separating the vortex liquid phase from the low-temperature irreversible region of the phase diagram [5,12]. In constant temperature, field-swept experiments, we observed a crossover in the sign of vu P /vT, which changed from positive at low temperatures (w4 K), to negative at high temperatures.…”

“…2 plots the JPR positions for data obtained from temperature sweeps at the three indicated measurement frequencies. The solid line represents the approximate crossover between the vu p /vT!0 and vu p /vT>0 regions, obtained from previously published data [5,12]. The inset to Fig.…”

“…In the region where vu p /vT!0, the field and temperature swept data agree quite well, while there is less agreement in the region where vu p /vT>0. Possible explanations for this slight [5,12]. The dash-dotted lines are fits to Eq.…”

“…In the past decade, an interlayer Josephson plasma resonance (JPR) has been observed in many layered superconductors, including the title compound [4,5], the HTS [6][7][8], and other organic conductors [9]. This JPR has been used extensively to investigate the Q2D vortex phase diagram, since the JPR frequency is strongly influenced by the interlayer spatial correlations between pancake vortices.…”

Terahertz Josephson plasma waves in layered superconductors: spectrum, generation, nonlinear and quantum phenomena

“…This phenomenon plays an essential role in the microwave absorption and reflectivity of layered superconductors [29][30][31][32][33][34][35][36][37][38][39] near the resonance frequency ω J . Besides this, the JPR has been introduced as a powerful tool providing unique information on the Josephson coupling of superconducting layers in HTS and on the structure of vortex phases in the presence of an applied magnetic field (see, e.g., Refs.…”