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arXiv · 1506.06639

Observation of a $d$-wave gap in electron-doped Sr$_2$IrO$_4$

Y. K. Kim·N. H. Sung·J. D. Denlinger·B. J. Kim
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Abstract

High temperature superconductivity in cuprates emerges out of a highly enigmatic `pseudogap' metal phase. The mechanism of high temperature superconductivity is likely encrypted in the elusive relationship between the two phases, which spectroscopically is manifested as Fermi arcs---disconnected segments of zero-energy states---collapsing into $d$-wave point nodes upon entering the superconducting phase. Here, we reproduce this distinct cuprate phenomenology in the 5$d$ transition-metal oxide Sr$_2$IrO$_4$. Using angle-resolved photoemission, we show that clean, low-temperature phase of 6-8$\%$ electron-doped Sr$_2$IrO$_4$ has gapless excitations only at four isolated points in the Brillouin zone with a predominant $d$-wave symmetry of the gap. Our work thus establishes a connection between the low-temperature $d$-wave instability and the previously reported high-temperature Fermi arcs in electron-doped Sr$_2$IrO$_4$. Although the physical origin of the $d$-wave gap remains to be understood, Sr$_2$IrO$_4$ is a first non-cuprate material to spectroscopically reproduce the complete phenomenology of the cuprates, thus offering a new material platform to investigate the relationship between the pseudogap and the $d$-wave gap.

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Y. K. Kim, N. H. Sung, J. D. Denlinger, B. J. Kim. 2015-06-25. Observation of a $d$-wave gap in electron-doped Sr$_2$IrO$_4$. https://doi.org/10.1038/nphys3503

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