Spontaneous Nernst effect in the iron-based superconductor <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Fe</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>+</mml:mo><mml:mi>y</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Te</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi>Se</mml:mi><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math>
Lu Chen, Ziji Xiang, Colin Tinsman, Bin Lei, Xianhui Chen, Genda Gu, Lü Li
Abstract
We present a study of the Nernst effect in an iron-based superconductor with a nontrivial band topology ${\mathrm{Fe}}_{1+y}{\mathrm{Te}}_{1\ensuremath{-}x}{\mathrm{Se}}_{x}$. A nonzero Nernst signal is observed in a narrow temperature region around the superconducting transition temperature ${T}_{c}$ at a zero field. This anomalous Nernst signal shows symmetric dependence on the external magnetic field and indicates an unconventional vortex contribution in an $s$-wave superconductor with a strong spin-orbit coupling, which is originated from the local magnetic moments of the interstitial Fe atoms. Our experiments also provide the first evidence of a locally broken time-reversal symmetry in bulk ${\mathrm{Fe}}_{1+y}{\mathrm{Te}}_{1\ensuremath{-}x}{\mathrm{Se}}_{x}$ single crystals.