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Title: Direct spectroscopic evidence for mixed-valence Tl in the low carrier-density superconductor Pb 1 - x Tl x Te

Abstract

Upon doping with Tl the narrow band-gap semiconductor PbTe exhibits anomalously high-temperature superconductivity despite a very low carrier-density as well as signatures of the Kondo effect despite an absence of magnetic moments. These phenomena have been explained by invoking 2e fluctuations of the valence of the Tl dopants, but a direct measurement of the mixed valency implied by such a mechanism has not been reported to date. Here in this work we present the unambiguous observation of multiple valences of Tl in Tl-doped PbTe via photoemission spectroscopy measurements. It is shown via a quantitative analysis that the suppression of the carrier density in compositions exhibiting superconductivity and Kondo-like behavior can be accounted for by mixed valency, thus arguing against a self-compensation scenario proposed elsewhere for this material and strengthening the case for valence fluctuation models. In addition to the identification of Tl+ and Tl3+ a possible third intermediate local charge-density is suggested by full fits to the data, the origins of which are also discussed but remain unclear.

Authors:
 [1];  [2];  [3];  [4];  [5];  [1];  [5]
  1. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials and Dept. of Applied Physics
  2. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy; Southern Univ. of Science and Technology (SUSTech), Shenzhen, Guangdong (China)
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy; Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
  4. Stanford Univ., CA (United States). Geballe Lab. for Advanced Materials and Dept. of Applied Physics; Univ. de Los Andes, Bogotá (Colombia). Dept. of Physics
  5. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1487218
Alternate Identifier(s):
OSTI ID: 1482285
Report Number(s):
IS-J-9823
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:  
AC02-07CH11358; FA9550-09-1-0583; DMR 9212658
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Physical Review. B
Additional Journal Information:
Journal Volume: 98; Journal Issue: 18; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY

Citation Formats

Walmsley, P., Liu, C., Palczewski, A. D., Giraldo-Gallo, P., Olson, C. G., Fisher, I. R., and Kaminski, A. Direct spectroscopic evidence for mixed-valence Tl in the low carrier-density superconductor Pb1-xTlxTe. United States: N. p., 2018. Web. doi:10.1103/physrevb.98.184506.
Walmsley, P., Liu, C., Palczewski, A. D., Giraldo-Gallo, P., Olson, C. G., Fisher, I. R., & Kaminski, A. Direct spectroscopic evidence for mixed-valence Tl in the low carrier-density superconductor Pb1-xTlxTe. United States. https://doi.org/10.1103/physrevb.98.184506
Walmsley, P., Liu, C., Palczewski, A. D., Giraldo-Gallo, P., Olson, C. G., Fisher, I. R., and Kaminski, A. 2018. "Direct spectroscopic evidence for mixed-valence Tl in the low carrier-density superconductor Pb1-xTlxTe". United States. https://doi.org/10.1103/physrevb.98.184506. https://www.osti.gov/servlets/purl/1487218.
@article{osti_1487218,
title = {Direct spectroscopic evidence for mixed-valence Tl in the low carrier-density superconductor Pb1-xTlxTe},
author = {Walmsley, P. and Liu, C. and Palczewski, A. D. and Giraldo-Gallo, P. and Olson, C. G. and Fisher, I. R. and Kaminski, A.},
abstractNote = {Upon doping with Tl the narrow band-gap semiconductor PbTe exhibits anomalously high-temperature superconductivity despite a very low carrier-density as well as signatures of the Kondo effect despite an absence of magnetic moments. These phenomena have been explained by invoking 2e fluctuations of the valence of the Tl dopants, but a direct measurement of the mixed valency implied by such a mechanism has not been reported to date. Here in this work we present the unambiguous observation of multiple valences of Tl in Tl-doped PbTe via photoemission spectroscopy measurements. It is shown via a quantitative analysis that the suppression of the carrier density in compositions exhibiting superconductivity and Kondo-like behavior can be accounted for by mixed valency, thus arguing against a self-compensation scenario proposed elsewhere for this material and strengthening the case for valence fluctuation models. In addition to the identification of Tl+ and Tl3+ a possible third intermediate local charge-density is suggested by full fits to the data, the origins of which are also discussed but remain unclear.},
doi = {10.1103/physrevb.98.184506},
url = {https://www.osti.gov/biblio/1487218}, journal = {Physical Review. B},
issn = {2469-9950},
number = 18,
volume = 98,
place = {United States},
year = {Thu Nov 15 00:00:00 EST 2018},
month = {Thu Nov 15 00:00:00 EST 2018}
}

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Cited by: 15 works
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Works referencing / citing this record:

Physics of Superconducting Transition Temperatures
journal, November 2019