Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3

Liam Trzaska; Lei Qiao; Matthew D Watson; Monica Ciomaga Hatnean; Igor Markovic; Edgar Abarca Morales; Tommaso Antonelli; Cephise Cacho; Geetha Balakrishnan; Wei Ren; Silvia Picozzi; Phil D. C. King

doi:10.1038/S41699-025-00526-8

Charge doping into spin minority states mediates doubling of T_C in ferromagnetic CrGeTe₃

Liam Trzaska, Lei Qiao, Matthew D Watson, Monica Ciomaga Hatnean, Igor Markovic, Edgar Abarca Morales, Tommaso Antonelli, Cephise Cacho, Geetha Balakrishnan, Wei Ren, Silvia Picozzi, Phil D. C. King^*

^*Corresponding author for this work

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

Abstract

The recent discovery of the persistence of long-range magnetic order when van der Waals magnets are thinned towards monolayers provides a tunable platform for engineering of novel magnetic structures and devices. Here, we study the evolution of the electronic structure of CrGeTe₃ as a function of surface electron doping. From angle-resolved photoemission, we observe spectroscopic fingerprints that this electron doping drives a marked increase in T_C, reaching values more than double that of the undoped material, in agreement with recent studies using electrostatic gating. Together with density functional theory calculations and Monte Carlo simulations, we show that, surprisingly, the increased T_C is mediated by the population of spin-minority Cr t_2g states, forming a half-metallic 2D electron gas. This promotes a novel variant of double exchange, and unlocks a significant influence of Ge – which was previously thought to be electronically inert in this system – in mediating Cr-Cr exchange.

Original language	English
Article number	4
Number of pages	7
Journal	npj 2D Materials and Applications
Volume	9
DOIs	https://doi.org/10.1038/S41699-025-00526-8
Publication status	Published - 17 Jan 2025

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1 Active
2 Finished

Controlling and integrating 2D magnetism: Controlling and integrating 2D magnetism in epitaxial van der Waals heterostructures
King, P. (PI) & Wahl, P. (CoI)
EPSRC
1/08/23 → 31/07/26
Project: Standard
An electronic structure perspective: An electronic structure perspective on quasi-2D magnetism in layered chalcogenides
King, P. (PI)
The Royal Society
15/02/23 → 14/02/25
Project: Standard
Engineered Quantum States: Engineered quantum states via atmoic-scale assembly of artificial 2D heterostructures
King, P. (PI)
The Leverhulme Trust
1/08/17 → 31/07/22
Project: Standard

Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3 (dataset)
Trzaska, L. (Creator), Qiao, L. (Creator), Watson, M. D. (Creator), Hatnean, M. (Creator), Markovic, I. (Creator), Abarca Morales, E. (Creator), Antonelli, T. (Creator), Cacho, C. (Creator), Balakrishnan, G. (Creator), ren, W. (Creator), Picozzi, S. (Creator) & King, P. (Creator), University of St Andrews, 17 Jan 2025
DOI: 10.17630/d2994e11-d310-46f1-9fa3-927d9895443f
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Cite this

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title = "Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3",

abstract = "The recent discovery of the persistence of long-range magnetic order when van der Waals magnets are thinned towards monolayers provides a tunable platform for engineering of novel magnetic structures and devices. Here, we study the evolution of the electronic structure of CrGeTe3 as a function of surface electron doping. From angle-resolved photoemission, we observe spectroscopic fingerprints that this electron doping drives a marked increase in TC, reaching values more than double that of the undoped material, in agreement with recent studies using electrostatic gating. Together with density functional theory calculations and Monte Carlo simulations, we show that, surprisingly, the increased TC is mediated by the population of spin-minority Cr t2g states, forming a half-metallic 2D electron gas. This promotes a novel variant of double exchange, and unlocks a significant influence of Ge – which was previously thought to be electronically inert in this system – in mediating Cr-Cr exchange.",

author = "Liam Trzaska and Lei Qiao and Watson, {Matthew D} and Hatnean, {Monica Ciomaga} and Igor Markovic and {Abarca Morales}, Edgar and Tommaso Antonelli and Cephise Cacho and Geetha Balakrishnan and Wei Ren and Silvia Picozzi and King, {Phil D. C.}",

note = "Funding: We gratefully acknowledge support from The Leverhulme Trust via Grant No. RL-2016-006, and the UK Engineering and Physical Sciences Research Council via Grant Nos. EP/X015556/1, EP/T005963/1, and EP/N032128/1. P.K. and S.P. acknowledge support from the Royal Society through the International Exchange grant IEC\R2\222041. IM and EAM gratefully acknowledge studentship support from the International Max Planck Research School for Chemistry and Physics of Quantum Materials. We thank Diamond Light Source for access to Beamline I05 (Proposals SI21986 and SI25564), which contributed to the results presented here. S.P. acknowledges support from the Ministry of University and Research (MUR) PRIN 2022 project “SORBET - Spin ORBit Effects in Two-dimensional magnets”, project No. 2022ZY8HJY. L.Q. acknowledges the support from China Scholarship Council, W.R. acknowledges the support from the National Natural Science Foundation of China (12074241, 11929401, 52120204), and the Science and Technology Commission of Shanghai Municipality (22XD1400900, 20501130600). ",

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doi = "10.1038/S41699-025-00526-8",

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T1 - Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3

AU - Trzaska, Liam

AU - Qiao, Lei

AU - Watson, Matthew D

AU - Hatnean, Monica Ciomaga

AU - Markovic, Igor

AU - Abarca Morales, Edgar

AU - Antonelli, Tommaso

AU - Cacho, Cephise

AU - Balakrishnan, Geetha

AU - Ren, Wei

AU - Picozzi, Silvia

AU - King, Phil D. C.

N1 - Funding: We gratefully acknowledge support from The Leverhulme Trust via Grant No. RL-2016-006, and the UK Engineering and Physical Sciences Research Council via Grant Nos. EP/X015556/1, EP/T005963/1, and EP/N032128/1. P.K. and S.P. acknowledge support from the Royal Society through the International Exchange grant IEC\R2\222041. IM and EAM gratefully acknowledge studentship support from the International Max Planck Research School for Chemistry and Physics of Quantum Materials. We thank Diamond Light Source for access to Beamline I05 (Proposals SI21986 and SI25564), which contributed to the results presented here. S.P. acknowledges support from the Ministry of University and Research (MUR) PRIN 2022 project “SORBET - Spin ORBit Effects in Two-dimensional magnets”, project No. 2022ZY8HJY. L.Q. acknowledges the support from China Scholarship Council, W.R. acknowledges the support from the National Natural Science Foundation of China (12074241, 11929401, 52120204), and the Science and Technology Commission of Shanghai Municipality (22XD1400900, 20501130600).

PY - 2025/1/17

Y1 - 2025/1/17

N2 - The recent discovery of the persistence of long-range magnetic order when van der Waals magnets are thinned towards monolayers provides a tunable platform for engineering of novel magnetic structures and devices. Here, we study the evolution of the electronic structure of CrGeTe3 as a function of surface electron doping. From angle-resolved photoemission, we observe spectroscopic fingerprints that this electron doping drives a marked increase in TC, reaching values more than double that of the undoped material, in agreement with recent studies using electrostatic gating. Together with density functional theory calculations and Monte Carlo simulations, we show that, surprisingly, the increased TC is mediated by the population of spin-minority Cr t2g states, forming a half-metallic 2D electron gas. This promotes a novel variant of double exchange, and unlocks a significant influence of Ge – which was previously thought to be electronically inert in this system – in mediating Cr-Cr exchange.

AB - The recent discovery of the persistence of long-range magnetic order when van der Waals magnets are thinned towards monolayers provides a tunable platform for engineering of novel magnetic structures and devices. Here, we study the evolution of the electronic structure of CrGeTe3 as a function of surface electron doping. From angle-resolved photoemission, we observe spectroscopic fingerprints that this electron doping drives a marked increase in TC, reaching values more than double that of the undoped material, in agreement with recent studies using electrostatic gating. Together with density functional theory calculations and Monte Carlo simulations, we show that, surprisingly, the increased TC is mediated by the population of spin-minority Cr t2g states, forming a half-metallic 2D electron gas. This promotes a novel variant of double exchange, and unlocks a significant influence of Ge – which was previously thought to be electronically inert in this system – in mediating Cr-Cr exchange.

U2 - 10.1038/S41699-025-00526-8

DO - 10.1038/S41699-025-00526-8

M3 - Article

SN - 2397-7132

VL - 9

JO - npj 2D Materials and Applications

JF - npj 2D Materials and Applications

M1 - 4

ER -

Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3

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Controlling and integrating 2D magnetism: Controlling and integrating 2D magnetism in epitaxial van der Waals heterostructures

An electronic structure perspective: An electronic structure perspective on quasi-2D magnetism in layered chalcogenides

Engineered Quantum States: Engineered quantum states via atmoic-scale assembly of artificial 2D heterostructures

Datasets

Charge doping into spin minority states mediates doubling of TC in ferromagnetic CrGeTe3 (dataset)

Cite this

Charge doping into spin minority states mediates doubling of T_C in ferromagnetic CrGeTe₃