Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe2

Tommaso Antonelli; Warda Rahim; Matthew D. Watson; Akhil Rajan; Oliver J. Clark; Alisa Danilenko; Kaycee Underwood; Igor Marković; Edgar Abarca-Morales; Seán R. Kavanagh; P. Le Fèvre; F. Bertran; K. Rossnagel; David O. Scanlon; Phil D.C. King

doi:10.1038/s41535-022-00508-9

Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe₂

Tommaso Antonelli^*, Warda Rahim, Matthew D. Watson, Akhil Rajan, Oliver J. Clark, Alisa Danilenko, Kaycee Underwood, Igor Marković, Edgar Abarca-Morales, Seán R. Kavanagh, P. Le Fèvre, F. Bertran, K. Rossnagel, David O. Scanlon, Phil D.C. King^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

Reducing the thickness of a material to its two-dimensional (2D) limit can have dramatic consequences for its collective electronic states, including magnetism, superconductivity, and charge and spin ordering. An extreme case is TiTe₂, where a charge density wave (CDW) emerges in the single-layer, which is absent for the bulk compound, and whose origin is still poorly understood. Here, we investigate the electronic band structure evolution across this CDW transition using temperature-dependent angle-resolved photoemission spectroscopy. Our study reveals an orbital-selective band hybridisation between the backfolded conduction and valence bands occurring at the CDW phase transition, which in turn leads to a significant electronic energy gain, underpinning the CDW transition. For the bulk compound, we show how this energy gain is almost completely suppressed due to the three-dimensionality of the electronic band structure, including via a k_z-dependent band inversion which switches the orbital character of the valence states. Our study thus sheds new light on how control of the electronic dimensionality can be used to trigger the emergence of new collective states in 2D materials.

Original language	English
Article number	98
Number of pages	10
Journal	npj Quantum Materials
Volume	7
Issue number	1
DOIs	https://doi.org/10.1038/s41535-022-00508-9
Publication status	Published - 27 Sept 2022

Bibliographical note

Funding Information:
We thank Sebastian Buchberger, Brendan Edwards, Lewis Hart, Chris Hooley, Federico Mazzola, Martin McClaren, Philip Murgatroyd, Luke Rhode and Gesa Siemann for useful discussions and technical assistance. We gratefully acknowledge support from the Leverhulme Trust and the Royal Society. Via membership of the UK’s HEC Materials Chemistry Consortium, which is funded by the EPSRC (EP/L000202, EP/R029431, EP/T022213), this work used the ARCHER2 UK National Supercomputing Service ( www.archer2.ac.uk ) and the UK Materials and Molecular Modelling (MMM) Hub (Thomas - EP/P020194 & Young - EP/T022213). W.R. is grateful to University College London for awarding a Graduate Research Scholarship and an Overseas Research Scholarship. O.J.C. and K.U. acknowledge PhD studentship support from the UK Engineering and Physical Sciences Research Council (EPSRC, Grant Nos. EP/K503162/1 and EP/L015110/1). I.M. and E.A.-M. acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials. S.R.K. acknowledges the EPSRC Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM, EP/S023259/1) for funding a PhD studentship. The MBE growth facility was funded through an EPSRC strategic equipment grant: EP/M023958/1. We thank SOLEIL synchrotron for access to the CASSIOPEE beamline (proposal Nos. 20181599 and 20171202). The research leading to this result has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.

Publisher Copyright:
© 2022, The Author(s).

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials
Condensed Matter Physics

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Cite this

Antonelli, T., Rahim, W., Watson, M. D., Rajan, A., Clark, O. J., Danilenko, A., Underwood, K., Marković, I., Abarca-Morales, E., Kavanagh, S. R., Le Fèvre, P., Bertran, F., Rossnagel, K., Scanlon, D. O., & King, P. D. C. (2022). Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe₂. npj Quantum Materials, 7(1), Article 98. https://doi.org/10.1038/s41535-022-00508-9

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title = "Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe2",

abstract = "Reducing the thickness of a material to its two-dimensional (2D) limit can have dramatic consequences for its collective electronic states, including magnetism, superconductivity, and charge and spin ordering. An extreme case is TiTe2, where a charge density wave (CDW) emerges in the single-layer, which is absent for the bulk compound, and whose origin is still poorly understood. Here, we investigate the electronic band structure evolution across this CDW transition using temperature-dependent angle-resolved photoemission spectroscopy. Our study reveals an orbital-selective band hybridisation between the backfolded conduction and valence bands occurring at the CDW phase transition, which in turn leads to a significant electronic energy gain, underpinning the CDW transition. For the bulk compound, we show how this energy gain is almost completely suppressed due to the three-dimensionality of the electronic band structure, including via a kz-dependent band inversion which switches the orbital character of the valence states. Our study thus sheds new light on how control of the electronic dimensionality can be used to trigger the emergence of new collective states in 2D materials.",

author = "Tommaso Antonelli and Warda Rahim and Watson, {Matthew D.} and Akhil Rajan and Clark, {Oliver J.} and Alisa Danilenko and Kaycee Underwood and Igor Markovi{\'c} and Edgar Abarca-Morales and Kavanagh, {Se{\'a}n R.} and {Le F{\`e}vre}, P. and F. Bertran and K. Rossnagel and Scanlon, {David O.} and King, {Phil D.C.}",

note = "Funding Information: We thank Sebastian Buchberger, Brendan Edwards, Lewis Hart, Chris Hooley, Federico Mazzola, Martin McClaren, Philip Murgatroyd, Luke Rhode and Gesa Siemann for useful discussions and technical assistance. We gratefully acknowledge support from the Leverhulme Trust and the Royal Society. Via membership of the UK{\textquoteright}s HEC Materials Chemistry Consortium, which is funded by the EPSRC (EP/L000202, EP/R029431, EP/T022213), this work used the ARCHER2 UK National Supercomputing Service ( www.archer2.ac.uk ) and the UK Materials and Molecular Modelling (MMM) Hub (Thomas - EP/P020194 & Young - EP/T022213). W.R. is grateful to University College London for awarding a Graduate Research Scholarship and an Overseas Research Scholarship. O.J.C. and K.U. acknowledge PhD studentship support from the UK Engineering and Physical Sciences Research Council (EPSRC, Grant Nos. EP/K503162/1 and EP/L015110/1). I.M. and E.A.-M. acknowledge studentship support from the International Max-Planck Research School for Chemistry and Physics of Quantum Materials. S.R.K. acknowledges the EPSRC Centre for Doctoral Training in the Advanced Characterisation of Materials (CDT-ACM, EP/S023259/1) for funding a PhD studentship. The MBE growth facility was funded through an EPSRC strategic equipment grant: EP/M023958/1. We thank SOLEIL synchrotron for access to the CASSIOPEE beamline (proposal Nos. 20181599 and 20171202). The research leading to this result has been supported by the project CALIPSOplus under Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. Publisher Copyright: {\textcopyright} 2022, The Author(s).",

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Antonelli, T, Rahim, W, Watson, MD, Rajan, A, Clark, OJ, Danilenko, A, Underwood, K, Marković, I, Abarca-Morales, E, Kavanagh, SR, Le Fèvre, P, Bertran, F, Rossnagel, K, Scanlon, DO & King, PDC 2022, 'Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe₂', npj Quantum Materials, vol. 7, no. 1, 98. https://doi.org/10.1038/s41535-022-00508-9

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T1 - Orbital-selective band hybridisation at the charge density wave transition in monolayer TiTe2

AU - Antonelli, Tommaso

AU - Rahim, Warda

AU - Watson, Matthew D.

AU - Rajan, Akhil

AU - Clark, Oliver J.

AU - Danilenko, Alisa

AU - Underwood, Kaycee

AU - Marković, Igor

AU - Abarca-Morales, Edgar

AU - Kavanagh, Seán R.

AU - Le Fèvre, P.

AU - Bertran, F.

AU - Rossnagel, K.

AU - Scanlon, David O.

AU - King, Phil D.C.

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PY - 2022/9/27

Y1 - 2022/9/27

N2 - Reducing the thickness of a material to its two-dimensional (2D) limit can have dramatic consequences for its collective electronic states, including magnetism, superconductivity, and charge and spin ordering. An extreme case is TiTe2, where a charge density wave (CDW) emerges in the single-layer, which is absent for the bulk compound, and whose origin is still poorly understood. Here, we investigate the electronic band structure evolution across this CDW transition using temperature-dependent angle-resolved photoemission spectroscopy. Our study reveals an orbital-selective band hybridisation between the backfolded conduction and valence bands occurring at the CDW phase transition, which in turn leads to a significant electronic energy gain, underpinning the CDW transition. For the bulk compound, we show how this energy gain is almost completely suppressed due to the three-dimensionality of the electronic band structure, including via a kz-dependent band inversion which switches the orbital character of the valence states. Our study thus sheds new light on how control of the electronic dimensionality can be used to trigger the emergence of new collective states in 2D materials.

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