Research Status In a crystal with a sub-lattice of localized f-electron states, the Kondo effect generates a heavy-fermion band structure. At high temperatures, a conventional (light) electronic band coexists with localized f-electron states on each magnetic atom. At lower temperatures, hybridization between this light band and the f-electron states results in opening a hybridization gap ΔHF(k), and its splitting into two new very flat bands with greatly enhanced density-of-electronic-states N(E) within just a few meV of EF. We developed a dilution-refrigerator-based mK SISTM instrument for mapping simultaneously the r-space and k-space electronic structure of heavy-fermion systems at temperatures down to 20 mK. Demonstration of the feasibility of this approach for visualizing heavy-fermion formation, and measuring heavy-fermion band-structures, launched the field of STM studies of heavy fermions (Nature 465, 570 (2010)). Fig. 4 A) URu2Si2 surface with Th substitution sites dark; B) the expected heavy-fermion band formation due to hybridization of the localized/magnetic Ur electrons with delocalized Ru electrons; C) our QPI measured heavy-fermion band formation in of URu2Si2. |
Research Plans The capability to image heavy fermions (Fig. 4) opens exciting new avenues for research into strongly entangled electronic quantum matter. |