Inhomogeneous Kondo-lattice in geometrically frustrated Pr${}_2$Ir${}_2$O${}_7$

Abstract

Magnetic fluctuations induced by geometric frustration of local Ir-spins disturb the formation of long range magnetic order in the family of pyrochlore iridates, R${}_2$Ir${}_2$O${}_7$ (R = lanthanide)${}^1$. As a consequence, Pr${}_2$Ir${}_2$O${}_7$ lies at a tuning-free antiferromagnetic-to-paramagnetic quantum critical point and exhibits a diverse array of complex phenomena including Kondo effect, biquadratic band structure, metallic spin-liquid (MSL), and anomalous Hall effect${}^{2-5}$. Using spectroscopic imaging with the scanning tunneling microscope, complemented with machine learning K-means clustering analysis, density functional theory, and theoretical modeling, we probe the local electronic states in single crystal of Pr${}_2$Ir${}_2$O${}_7$ and discover an electronic phase separation. Nanoscale regions with a well-defined Kondo resonance are interweaved with a non-magnetic metallic phase with Kondo-destruction. Remarkably, the spatial nanoscale patterns display a correlation-driven fractal geometry with power-law behavior extended over two and a half decades, consistent with being in proximity to a critical point. Our discovery reveals a new nanoscale tuning route, viz. using a spatial variation of the electronic potential as a means of adjusting the balance between Kondo entanglement and geometric frustration.

arXiv commentNature Communications (in press)

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• Nature of the unconventional heavy fermion Kondo state in monolayer CeSiI
• Weyl-Luttinger phase transition in pyrochlore iridates revealed by Raman scattering
• Many-body electronic structure in pyrochlore superconductor CsBi2 and spin liquid Pr2Ir2O7
• Anomalous Hall effect and quantum criticality in geometrically frustrated heavy fermion metals
• Emergent Chiral Metal near a Kondo Breakdown Quantum Phase Transition