Strong correlations and orbital texture in single-layer 1T-TaSe2

Abstract

Strong electron correlation can induce Mott insulating behaviour and produce intriguing states of matter such as unconventional superconductivity and quantum spin liquids. Recent advances in van der Waals material synthesis enable the exploration of Mott systems in the two-dimensional limit. Here we report characterization of the local electronic properties of single- and few-layer 1T-TaSe2 via spatial- and momentum-resolved spectroscopy involving scanning tunnelling microscopy and angle-resolved photoemission. Our results indicate that electron correlation induces a robust Mott insulator state in single-layer 1T-TaSe2 that is accompanied by unusual orbital texture. Interlayer coupling weakens the insulating phase, as shown by reduction of the energy gap and quenching of the correlation-driven orbital texture in bilayer and trilayer 1T-TaSe2. This establishes single-layer 1T-TaSe2 as a useful platform for investigating strong correlation physics in two dimensions.

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Fig. 1: Structure of single-layer 1T-TaSe2 in the star-of-David CDW phase.
Fig. 2: ARPES and DFT + U band structure of single-layer 1T-TaSe2.
Fig. 3: Experimental energy-resolved unusual orbital texture of single-layer 1T-TaSe2.
Fig. 4: Energy gap reduction and quenching of unusual orbital texture in few-layer 1T-TaSe2.
Fig. 5: Theoretical orbital texture of single-layer 1T-TaSe2 from DFT + U simulations.

Data availability

The data represented in Figs. 1f, 3a, 4 and 5a are available with the paper. All other data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.

Code availability

The codes used in this study are available from the corresponding author upon reasonable request.

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Acknowledgements

We thank P.A. Lee and D.-H. Lee for helpful discussions. This research was supported by the VdW Heterostructure programme (KCWF16) (STS measurements and DFT simulations) and the Advanced Light Source (sample growth and ARPES measurements) funded by the Director, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, of the US Department of Energy under contract no. DE-AC02-05CH11231. Support was also provided by National Science Foundation award DMR-1508412 (DFT + U simulations), award DMR-1926004 (theoretical STS and ARPES analyses), award DMR-1507141 (electrostatic analysis) and award EFRI-1433307 (CDW model development). The work at the Stanford Institute for Materials and Energy Sciences and Stanford University (sample growth) was supported by the DOE Office of Basic Energy Sciences, Division of Material Science. Low-energy electron diffraction measurements were supported by the National Natural Science Foundation of China (grant no. 11227902). S.T. acknowledges the support by the CPSF-CAS Joint Foundation for Excellent Postdoctoral Fellows. H.R. acknowledges fellowship support from NRF, Korea through Max Planck Korea/POSTECH Research Initiatives no. 2016K1A4A4A01922028. H.-Z.T. acknowledges fellowship support from the Shenzhen Peacock Plan (grant numbers 827-000113, KQJSCX20170727100802505 and KQTD2016053112042971).

Author information

Y.C., W.R. and M.F.C. initiated and conceived the research. Y.C., W.R., H.-Z.T., R.L., S.K., F.L. and C.J. carried out STM/STS measurements and analyses. M.F.C. supervised STM/STS measurements and analyses. S.T., H.R., H.X. and T.J. performed sample growth and ARPES measurements. S.-K.M., Z.-X.S., J.A.S. and Z.L. supervised sample growth and ARPES measurements. M.W. performed DFT calculations and theoretical analyses. S.G.L. supervised DFT calculations and theoretical analyses. J.E.M. performed electrostatic modelling. O.R.A. and A.Y.L. provided support for development of the CDW model. Y.C., W.R. and M.F.C. wrote the manuscript with help from all authors. All authors contributed to the scientific discussion.

Correspondence to Michael F. Crommie.

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Supplementary Notes 1–5 and Figs. 1–24.

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Chen, Y., Ruan, W., Wu, M. et al. Strong correlations and orbital texture in single-layer 1T-TaSe2. Nat. Phys. 16, 218–224 (2020). https://doi.org/10.1038/s41567-019-0744-9

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