*Review* **Interplay between Vortex Dynamics and Superconducting Gap Structure in Layered Organic Superconductors**

**Syuma Yasuzuka**

Research Center for Condensed Matter Physics, Hiroshima Institute of Technology, Hiroshima 731-5193, Japan; yasuzuka@cc.it-hiroshima.ac.jp; Tel.: +81-82-921-6930

**Abstract:** Layered organic superconductors motivate intense investigations because they provide various unexpected issues associated with their low dimensionality and the strong electron correlation. Since layered organic superconductors possess simple Fermi surface geometry and they often share similarities to the high temperature oxide superconductors and heavy fermion compounds, research on layered organic superconductors is suitable for understanding the essence and nature of strongly correlated electron systems. In strongly correlated electron systems, one of the central problems concerning the superconducting (SC) state is the symmetry of the SC gap, which is closely related to the paring mechanism. Thus, experimental determination of the SC gap structure is of essential importance. In this review, we present the experimental results for the in-plane angular variation of the flux-flow resistance in layered organic superconductors K-(ET)2Cu(NCS)2, β"-(ET)2SF5CH2CF2SO3, and λ-(BETS)2GaCl4. The interplay between the vortex dynamics and nodal structures is discussed for these superconductors.

**Keywords:** layered organic conductor; unconventional superconductivity; vortex dynamics; *d*-wave pairing symmetry; superconducting gap structure; magnetic field; flux-flow resistivity
