Far-infrared optical conductivity gap in superconducting MgB2 films.
We report the first study of the optical conductivity of MgB2 covering the range of its lowest-energy superconducting gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity sigma(omega) of thin films. The imaginary part reveals an inductive response due to the emergence of the superconducting condensate. The real part exhibits a strong depletion of oscillator strength near 5 meV resulting from the opening of a superconducting energy gap. The gap ratio of 2Delta0/k(B)TC approximately 1.9 is well below the weak-coupling value, pointing to complex behavior in this novel superconductor.
Kaindl
Robert A
RA
Department of Physics, University of California at Berkeley, and Materials Sciences Division, E. O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Carnahan
Marc A
MA
Orenstein
Joseph
J
Chemla
Daniel S
DS
Christen
Hans M
HM
Zhai
Hong-Ying
HY
Paranthaman
Mariappan
M
Lowndes
Doug H
DH