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Title: Dynamical Bonding Driving Mixed Valency in a Metal Boride

Journal Article · · Angewandte Chemie (International Edition)

Abstract Samarium hexaboride is an anomaly, having many exotic and seemingly mutually incompatible properties. It was proposed to be a mixed‐valent semiconductor, and later a topological Kondo insulator, and yet has a Fermi surface despite being an insulator. We propose a new and unified understanding of SmB 6 centered on the hitherto unrecognized dynamical bonding effect: the coexistence of two Sm−B bonding modes within SmB 6 , corresponding to different oxidation states of the Sm. The mixed valency arises in SmB 6 from thermal population of these distinct minima enabled by motion of B. Our model simultaneously explains the thermal valence fluctuations, appearance of magnetic Fermi surface, excess entropy at low temperatures, pressure‐induced phase transitions, and related features in Raman spectra and their unexpected dependence on temperature and boron isotope.

Research Organization:
Energy Frontier Research Centers (EFRC) (United States). Institute for Quantum Matter (IQM); Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
89233218CNA000001; SC0019331
OSTI ID:
1671085
Alternate ID(s):
OSTI ID: 1608371
Report Number(s):
LA-UR-19-30421
Journal Information:
Angewandte Chemie (International Edition), Vol. 59, Issue 27; ISSN 1433-7851
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English

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