# Surface waves versus negative refractive index in layered superconductors 

V.A. Golick, 1 D.V. Kadygrob, 2 V.A. Yampol’skii, 1, 2, 3 A.L. Rakhmanov, 3, 4 B.A. Ivanov, 3, 5, 6 and Franco Nori 3, 7 

$^{1}$V.N. Karazin Kharkov National University, 61077 Kharkov, Ukraine 

$^{2}$A.Ya. Usikov Institute for Radiophysics and Electronics, Ukrainian Academy of Sciences, 61085 Kharkov, Ukraine 

$^{3}$Advanced Science Institute, The Institute of Physical and Chemical Research (RIKEN), Saitama, 351-0198, Japan 

$^{4}$Institute for Theoretical and Applied Electrodynamics Russian Acad. Sci., 125412 Moscow, Russia 

$^{5}$Institute of Magnetism, Ukrainian Academy of Sciences, 03142 Kiev, Ukraine 

$^{6}$National T. Shevchenko University of Kiev, 03127 Kiev, Ukraine 

$^{7}$Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA 

## Abstract 

We predict a new branch of surface Josephson plasma waves (SJPWs) in layered superconductors for frequencies higher than the Josephson plasma frequency. In this frequency range, the permit- tivity tensor components along and transverse to the layers have different signs, which is usually associated with negative refraction. However, for these frequencies, the bulk Josephson plasma waves cannot be matched with the incident and reflected waves in the vacuum, and, instead of the negative-refractive properties, abnormal surface modes appear within the frequency band ex- pected for bulk modes. We also discuss the excitation of high-frequency SJPWs by means of the attenuated-total-reflection method. 

PACS numbers: 74.25.N-, 42.25.Bs 

