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Title: Characterization of collective ground states in single-layer NbSe 2

Abstract

Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge density wave (CDW) order and superconductivity. In bulk NbSe 2 a CDW sets in at T CDW = 33 K and superconductivity sets in at T c = 7.2 K. Below T c these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional (2D) layer of NbSe 2 by means of low-temperature scanning tunnelling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and electrical transport measurements. We demonstrate that 3 × 3 CDW order in NbSe 2 remains intact in two dimensions. Superconductivity also still remains in the 2D limit, but its onset temperature is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified (compared to bulk) electronic structure of single-layer NbSe 2, thus providing insight into CDW formation and superconductivity in this model strongly correlated system.

Authors:
 [1];  [2]; ORCiD logo [3];  [2];  [2];  [4];  [5];  [6];  [7];  [2];  [8]; ORCiD logo [6];  [2];  [9];  [6];  [10];  [9]
  1. Univ. of California, Berkeley, CA (United States); CIC nanoGUNE, Donostia-San Sebastion (Spain); Basque Foundation for Science, Bilbao (Spain)
  2. Univ. of California, Berkeley, CA (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS); SLAC National Accelerator Lab., Menlo Park, CA (United States); Nanjing Univ. (China)
  4. Univ. of California, Berkeley, CA (United States); Tsinghua Univ., Beijing (China)
  5. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); California State Univ. (CalState), Long Beach, CA (United States)
  6. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  7. Univ. of California, Berkeley, CA (United States); Monash Univ., Melbourne, VIC (Australia)
  8. Univ. of California, Berkeley, CA (United States); Vienna Univ. of Technology (Austria). Inst. of Applied Physics
  9. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  10. SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1530224
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Nature Physics
Additional Journal Information:
Journal Volume: 12; Journal Issue: 1; Journal ID: ISSN 1745-2473
Publisher:
Nature Publishing Group (NPG)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS

Citation Formats

Ugeda, Miguel M., Bradley, Aaron J., Zhang, Yi, Onishi, Seita, Chen, Yi, Ruan, Wei, Ojeda-Aristizabal, Claudia, Ryu, Hyejin, Edmonds, Mark T., Tsai, Hsin-Zon, Riss, Alexander, Mo, Sung-Kwan, Lee, Dunghai, Zettl, Alex, Hussain, Zahid, Shen, Zhi-Xun, and Crommie, Michael F. Characterization of collective ground states in single-layer NbSe2. United States: N. p., 2015. Web. doi:10.1038/nphys3527.
Ugeda, Miguel M., Bradley, Aaron J., Zhang, Yi, Onishi, Seita, Chen, Yi, Ruan, Wei, Ojeda-Aristizabal, Claudia, Ryu, Hyejin, Edmonds, Mark T., Tsai, Hsin-Zon, Riss, Alexander, Mo, Sung-Kwan, Lee, Dunghai, Zettl, Alex, Hussain, Zahid, Shen, Zhi-Xun, & Crommie, Michael F. Characterization of collective ground states in single-layer NbSe2. United States. doi:10.1038/nphys3527.
Ugeda, Miguel M., Bradley, Aaron J., Zhang, Yi, Onishi, Seita, Chen, Yi, Ruan, Wei, Ojeda-Aristizabal, Claudia, Ryu, Hyejin, Edmonds, Mark T., Tsai, Hsin-Zon, Riss, Alexander, Mo, Sung-Kwan, Lee, Dunghai, Zettl, Alex, Hussain, Zahid, Shen, Zhi-Xun, and Crommie, Michael F. Mon . "Characterization of collective ground states in single-layer NbSe2". United States. doi:10.1038/nphys3527. https://www.osti.gov/servlets/purl/1530224.
@article{osti_1530224,
title = {Characterization of collective ground states in single-layer NbSe2},
author = {Ugeda, Miguel M. and Bradley, Aaron J. and Zhang, Yi and Onishi, Seita and Chen, Yi and Ruan, Wei and Ojeda-Aristizabal, Claudia and Ryu, Hyejin and Edmonds, Mark T. and Tsai, Hsin-Zon and Riss, Alexander and Mo, Sung-Kwan and Lee, Dunghai and Zettl, Alex and Hussain, Zahid and Shen, Zhi-Xun and Crommie, Michael F.},
abstractNote = {Layered transition metal dichalcogenides are ideal systems for exploring the effects of dimensionality on correlated electronic phases such as charge density wave (CDW) order and superconductivity. In bulk NbSe2 a CDW sets in at T CDW = 33 K and superconductivity sets in at Tc = 7.2 K. Below Tc these electronic states coexist but their microscopic formation mechanisms remain controversial. Here we present an electronic characterization study of a single two-dimensional (2D) layer of NbSe2 by means of low-temperature scanning tunnelling microscopy/spectroscopy (STM/STS), angle-resolved photoemission spectroscopy (ARPES), and electrical transport measurements. We demonstrate that 3 × 3 CDW order in NbSe2 remains intact in two dimensions. Superconductivity also still remains in the 2D limit, but its onset temperature is depressed to 1.9 K. Our STS measurements at 5 K reveal a CDW gap of Δ = 4 meV at the Fermi energy, which is accessible by means of STS owing to the removal of bands crossing the Fermi level for a single layer. Our observations are consistent with the simplified (compared to bulk) electronic structure of single-layer NbSe2, thus providing insight into CDW formation and superconductivity in this model strongly correlated system.},
doi = {10.1038/nphys3527},
journal = {Nature Physics},
number = 1,
volume = 12,
place = {United States},
year = {2015},
month = {11}
}

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Works referenced in this record:

Electrons in lattice fields
journal, July 1954


Two-dimensional atomic crystals
journal, July 2005

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