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arXiv · 2303.15432

Visualizing the atomic-scale origin of metallic behavior in Kondo insulators

Harris Pirie·Eric Mascot·Christian E. Matt·Yu Liu·Pengcheng Chen·M. H. Hamidian·Shanta Saha·Xiangfeng Wang·Johnpierre Paglione·Graeme Luke·David Goldhaber-Gordon·Cyrus F. Hirjibehedin·J. C. Séamus Davis·Dirk K. Morr·Jennifer E. Hoffman
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Abstract

A Kondo lattice is often electrically insulating at low temperatures. However, several recent experiments have detected signatures of bulk metallicity within this Kondo insulating phase. Here we visualize the real-space charge landscape within a Kondo lattice with atomic resolution using a scanning tunneling microscope. We discover nanometer-scale puddles of metallic conduction electrons centered around uranium-site substitutions in the heavy-fermion compound URu$_2$Si$_2$, and around samarium-site defects in the topological Kondo insulator SmB$_6$. These defects disturb the Kondo screening cloud, leaving behind a fingerprint of the metallic parent state. Our results suggest that the mysterious 3D quantum oscillations measured in SmB$_6$ could arise from these Kondo-lattice defects, although we cannot rule out other explanations. Our imaging technique could enable the development of atomic-scale charge sensors using heavy-fermion probes.

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Harris Pirie, Eric Mascot, Christian E. Matt, Yu Liu, Pengcheng Chen, M. H. Hamidian, Shanta Saha, Xiangfeng Wang, Johnpierre Paglione, Graeme Luke, David Goldhaber-Gordon, Cyrus F. Hirjibehedin, J. C. Séamus Davis, Dirk K. Morr, Jennifer E. Hoffman. 2023-03-27. Visualizing the atomic-scale origin of metallic behavior in Kondo insulators. https://doi.org/10.1126/science.abq5375

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