Checkerboard patterns of charge stripes in the two-gap superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>ZrB</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:math>
Н. Б. Болотина, О.Н. Хрыкина, A. N. Azarevich, N. Yu. Shitsevalova, В. Б. Филипов, S. Yu. Gavrilkin, K. V. Mitsen, В. В. Воронов, N. E. Sluchanko
Abstract
Inhomogeneous superconductivity was studied in ${\mathrm{ZrB}}_{12}$ $({T}_{\mathrm{c}}\ensuremath{\approx}6\phantom{\rule{0.16em}{0ex}}\mathrm{K})$ using heat capacity and x-ray diffraction data. Evidence of two-band superconductivity with two branches of upper critical field ${\mathbf{H}}_{c2}({T}_{c})$ is obtained in a magnetic field applied along the [110] axis of the crystal. On the contrary, at H || [100], a single dependence $\mathbf{H}{c}_{2}({T}_{c})$ was observed. This finding is consistent with the checkerboard-type patterns observed on the difference Fourier maps of the electron density distribution. These patterns are compared to those for the weakly coupled superconductor ${\mathrm{LuB}}_{12}$, ${T}_{\mathrm{c}}$ of which is 15 times lower than that of ${\mathrm{ZrB}}_{12}$. The probable nature of the two-gap superconductivity in ${\mathrm{ZrB}}_{12}$ is discussed.