skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Mott and generalized Wigner crystal states in WSe 2/WS 2 moiré superlattices

Abstract

Moiré superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moiré superlattices. Transition metal dichalcogenide moiré heterostructures provide another model system for the study of correlated quantum phenomena because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe 2/WS 2 moiré superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice. Furthermore, the spin–valley optical selection rules of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Here, our studies highlight the value of using moirémore » superlattices beyond graphene to explore correlated physics.« less

Authors:
 [1];  [1]; ORCiD logo [2]; ORCiD logo [1]; ORCiD logo [3]; ORCiD logo [4];  [4];  [4];  [5];  [5]; ORCiD logo [6]; ORCiD logo [7];  [7];  [5]; ORCiD logo [1];  [1]; ORCiD logo [1];  [8]
  1. University of California, Berkeley, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
  2. University of California, Berkeley, CA (United States); Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY (United States)
  3. University of California, Berkeley, CA (United States); Huazhong University of Science and Technology, Wuhan (China)
  4. University of California, Berkeley, CA (United States)
  5. Arizona State University, Tempe, AZ (United States)
  6. University of California, Berkeley, CA (United States); Lund University (Sweden)
  7. National Institute for Materials Science, Tsukuba (Japan)
  8. University of California, Berkeley, CA (United States); University of the Chinese Academy of Sciences, Beijing (China)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division
OSTI Identifier:
1670714
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Volume: 579; Journal Issue: 7799; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Quantum fluids and solids; Two-dimensional materials

Citation Formats

Regan, Emma C., Wang, Danqing, Jin, Chenhao, Bakti Utama, M. Iqbal, Gao, Beini, Zhao, Sihan, Zhao, Wenyu, Zhang, Zuocheng, Yumigeta, Kentaro, Blei, Mark, Carlström, Johan D., Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Crommie, Michael, Zettl, Alex, Wang, Feng, and Wei, Xin. Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices. United States: N. p., 2020. Web. doi:10.1038/s41586-020-2092-4.
Regan, Emma C., Wang, Danqing, Jin, Chenhao, Bakti Utama, M. Iqbal, Gao, Beini, Zhao, Sihan, Zhao, Wenyu, Zhang, Zuocheng, Yumigeta, Kentaro, Blei, Mark, Carlström, Johan D., Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Crommie, Michael, Zettl, Alex, Wang, Feng, & Wei, Xin. Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices. United States. doi:10.1038/s41586-020-2092-4.
Regan, Emma C., Wang, Danqing, Jin, Chenhao, Bakti Utama, M. Iqbal, Gao, Beini, Zhao, Sihan, Zhao, Wenyu, Zhang, Zuocheng, Yumigeta, Kentaro, Blei, Mark, Carlström, Johan D., Watanabe, Kenji, Taniguchi, Takashi, Tongay, Sefaattin, Crommie, Michael, Zettl, Alex, Wang, Feng, and Wei, Xin. Wed . "Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices". United States. doi:10.1038/s41586-020-2092-4.
@article{osti_1670714,
title = {Mott and generalized Wigner crystal states in WSe2/WS2 moiré superlattices},
author = {Regan, Emma C. and Wang, Danqing and Jin, Chenhao and Bakti Utama, M. Iqbal and Gao, Beini and Zhao, Sihan and Zhao, Wenyu and Zhang, Zuocheng and Yumigeta, Kentaro and Blei, Mark and Carlström, Johan D. and Watanabe, Kenji and Taniguchi, Takashi and Tongay, Sefaattin and Crommie, Michael and Zettl, Alex and Wang, Feng and Wei, Xin},
abstractNote = {Moiré superlattices can be used to engineer strongly correlated electronic states in two-dimensional van der Waals heterostructures, as recently demonstrated in the correlated insulating and superconducting states observed in magic-angle twisted-bilayer graphene and ABC trilayer graphene/boron nitride moiré superlattices. Transition metal dichalcogenide moiré heterostructures provide another model system for the study of correlated quantum phenomena because of their strong light–matter interactions and large spin–orbit coupling. However, experimental observation of correlated insulating states in this system is challenging with traditional transport techniques. Here we report the optical detection of strongly correlated phases in semiconducting WSe2/WS2 moiré superlattices. We use a sensitive optical detection technique and reveal a Mott insulator state at one hole per superlattice site and surprising insulating phases at 1/3 and 2/3 filling of the superlattice, which we assign to generalized Wigner crystallization on the underlying lattice. Furthermore, the spin–valley optical selection rules of transition metal dichalcogenide heterostructures allow us to optically create and investigate low-energy excited spin states in the Mott insulator. We measure a very long spin relaxation lifetime of many microseconds in the Mott insulating state, orders of magnitude longer than that of charge excitations. Here, our studies highlight the value of using moiré superlattices beyond graphene to explore correlated physics.},
doi = {10.1038/s41586-020-2092-4},
journal = {Nature (London)},
issn = {0028-0836},
number = 7799,
volume = 579,
place = {United States},
year = {2020},
month = {3}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on March 18, 2021
Publisher's Version of Record

Save / Share:

Works referenced in this record:

Correlated insulator behaviour at half-filling in magic-angle graphene superlattices
journal, March 2018


Unconventional superconductivity in magic-angle graphene superlattices
journal, March 2018


Evidence of a gate-tunable Mott insulator in a trilayer graphene moiré superlattice
journal, January 2019


Signatures of tunable superconductivity in a trilayer graphene moiré superlattice
journal, July 2019


Hubbard Model Physics in Transition Metal Dichalcogenide Moiré Bands
journal, July 2018


On the Interaction of Electrons in Metals
journal, December 1934


Flat Bands and Wigner Crystallization in the Honeycomb Optical Lattice
journal, August 2007


Doped Twisted Bilayer Graphene near Magic Angles: Proximity to Wigner Crystallization, Not Mott Insulation
journal, September 2018


Pressure-induced metal-insulator transition in twisted bilayer graphene
journal, May 2019


Control of valley polarization in monolayer MoS2 by optical helicity
journal, June 2012


Coupled Spin and Valley Physics in Monolayers of MoS 2 and Other Group-VI Dichalcogenides
journal, May 2012


Valley-selective circular dichroism of monolayer molybdenum disulphide
journal, January 2012

  • Cao, Ting; Wang, Gang; Han, Wenpeng
  • Nature Communications, Vol. 3, Issue 1
  • DOI: 10.1038/ncomms1882

Electronic structure of a single MoS2 monolayer
journal, May 2012


Shubnikov–de Haas Oscillations of High-Mobility Holes in Monolayer and Bilayer WSe 2 : Landau Level Degeneracy, Effective Mass, and Negative Compressibility
journal, February 2016


Spin-polarized electrons in monolayer MoS2
journal, March 2019

  • Roch, Jonas Gaël; Froehlicher, Guillaume; Leisgang, Nadine
  • Nature Nanotechnology, Vol. 14, Issue 5
  • DOI: 10.1038/s41565-019-0397-y

Giant Paramagnetism-Induced Valley Polarization of Electrons in Charge-Tunable Monolayer MoSe 2
journal, June 2017


Emerging Photoluminescence in Monolayer MoS2
journal, April 2010

  • Splendiani, Andrea; Sun, Liang; Zhang, Yuanbo
  • Nano Letters, Vol. 10, Issue 4, p. 1271-1275
  • DOI: 10.1021/nl903868w

Atomically Thin MoS2 A New Direct-Gap Semiconductor
journal, September 2010


The Basis of the Electron Theory of Metals, with Special Reference to the Transition Metals
journal, July 1949


Metal-insulator transitions
journal, October 1998

  • Imada, Masatoshi; Fujimori, Atsushi; Tokura, Yoshinori
  • Reviews of Modern Physics, Vol. 70, Issue 4, p. 1039-1263
  • DOI: 10.1103/RevModPhys.70.1039

Electrical contacts to two-dimensional semiconductors
journal, November 2015

  • Allain, Adrien; Kang, Jiahao; Banerjee, Kaustav
  • Nature Materials, Vol. 14, Issue 12
  • DOI: 10.1038/nmat4452

Observation of moiré excitons in WSe2/WS2 heterostructure superlattices
journal, February 2019


Ultrafast Charge Recombination in a Photoexcited Mott-Hubbard Insulator
journal, July 2013


Photoinduced transition from Mott insulator to metal in the undoped cuprates Nd 2 CuO 4 and La 2 CuO 4
journal, March 2011


Ultrafast optical spectroscopy of strongly correlated materials and high-temperature superconductors: a non-equilibrium approach
journal, March 2016


Observation of ultralong valley lifetime in WSe 2 /MoS 2 heterostructures
journal, July 2017


Imaging of pure spin-valley diffusion current in WS 2 -WSe 2 heterostructures
journal, May 2018


1T-TaS 2 as a quantum spin liquid
journal, June 2017

  • Law, K. T.; Lee, Patrick A.
  • Proceedings of the National Academy of Sciences, Vol. 114, Issue 27
  • DOI: 10.1073/pnas.1706769114

Weak Mott insulators on the triangular lattice: Possibility of a gapless nematic quantum spin liquid
journal, June 2010


One-Dimensional Electrical Contact to a Two-Dimensional Material
journal, October 2013


Second harmonic microscopy of monolayer MoS 2
journal, April 2013


Probing Symmetry Properties of Few-Layer MoS 2 and h-BN by Optical Second-Harmonic Generation
journal, June 2013

  • Li, Yilei; Rao, Yi; Mak, Kin Fai
  • Nano Letters, Vol. 13, Issue 7
  • DOI: 10.1021/nl401561r