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Title: Dynamical Bonding Driving Mixed Valency in a Metal Boride

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 SmB6 centered on the hitherto unrecognized dynamical bonding effect: the coexistence of two Sm-B bonding modes within SmB6, corresponding to different oxidation states of the Sm. The mixed valency arises in SmB6 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.

Authors:
ORCiD logo [1]; ORCiD logo [2];  [3];  [3];  [3];  [3];  [4];  [3]; ORCiD logo [2]
  1. Univ. of California, Los Angeles, CA (United States); Columbia Univ., New York, NY (United States)
  2. Univ. of California, Los Angeles, CA (United States)
  3. Johns Hopkins Univ., Baltimore, MD (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1671085
Alternate Identifier(s):
OSTI ID: 1608371
Report Number(s):
LA-UR-19-30421
Journal ID: ISSN 1433-7851
Grant/Contract Number:  
89233218CNA000001; SC0019331
Resource Type:
Accepted Manuscript
Journal Name:
Angewandte Chemie (International Edition)
Additional Journal Information:
Journal Name: Angewandte Chemie (International Edition); Journal Volume: 59; Journal Issue: 27; Journal ID: ISSN 1433-7851
Publisher:
Wiley
Country of Publication:
United States
Language:
English
Subject:
Material Science; chemical bonding; mixed valency; pressure induced phase transitions; Raman spectroscopy; samarium hexaboride

Citation Formats

Robinson, Paul J., Munarriz, Julen, Valentine, Michael E., Granmoe, Austin, Drichko, Natalia, Chamorro, Juan R., Rosa, Priscila F., McQueen, Tyrel M., and Alexandrova, Anastassia N. Dynamical Bonding Driving Mixed Valency in a Metal Boride. United States: N. p., 2020. Web. doi:10.1002/anie.202000945.
Robinson, Paul J., Munarriz, Julen, Valentine, Michael E., Granmoe, Austin, Drichko, Natalia, Chamorro, Juan R., Rosa, Priscila F., McQueen, Tyrel M., & Alexandrova, Anastassia N. Dynamical Bonding Driving Mixed Valency in a Metal Boride. United States. doi:10.1002/anie.202000945.
Robinson, Paul J., Munarriz, Julen, Valentine, Michael E., Granmoe, Austin, Drichko, Natalia, Chamorro, Juan R., Rosa, Priscila F., McQueen, Tyrel M., and Alexandrova, Anastassia N. Mon . "Dynamical Bonding Driving Mixed Valency in a Metal Boride". United States. doi:10.1002/anie.202000945.
@article{osti_1671085,
title = {Dynamical Bonding Driving Mixed Valency in a Metal Boride},
author = {Robinson, Paul J. and Munarriz, Julen and Valentine, Michael E. and Granmoe, Austin and Drichko, Natalia and Chamorro, Juan R. and Rosa, Priscila F. and McQueen, Tyrel M. and Alexandrova, Anastassia N.},
abstractNote = {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 SmB6 centered on the hitherto unrecognized dynamical bonding effect: the coexistence of two Sm-B bonding modes within SmB6, corresponding to different oxidation states of the Sm. The mixed valency arises in SmB6 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.},
doi = {10.1002/anie.202000945},
journal = {Angewandte Chemie (International Edition)},
number = 27,
volume = 59,
place = {United States},
year = {2020},
month = {4}
}

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