Magnetic ground states of honeycomb lattice Wigner crystals

Kaushal, Nitin; Morales-Durán, Nicolás; MacDonald, Allan H.; Dagotto, Elbio

doi:10.1038/s42005-022-01065-0

Cited by 10 publications

(4 citation statements)

References 67 publications

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“…Our work establishes the HTL as a platform for investigation of both honeycomb and triangular Hubbard systems, as well as their interplay [7]. Exploring the magnetic phase diagrams of the charge transfer insulating states [15,46] and honeycomb lattice Wigner crystals [23,24] are exciting future avenues to pursue. Further, the high tunability and large number of degrees of freedom available in this system could enable the exploration of Kondo interactions when ν h = 1 in the lowest Hubbard band while a higher energy, more dispersive orbital is partially filled [47,48].…”

Section: Discussionmentioning

confidence: 76%

“…Further, in semiconducting transition metal dichalcogenide (TMD) moiré systems, the Coulomb interaction strengths between particles in the moiré lattice can be continuously tuned via the moiré period [14,15]. Additionally, different real-space lattice geometries can be found in the low energy valence moiré bands, dependent on the valley degree of freedom: moiré orbitals on a triangular lattice are generally found for Kvalley moiré bands localized on a single atomic layer [14][15][16][17][18][19][20][21] while honeycomb lattices are found for Γ-valley moiré bands spread across each layer [22][23][24][25][26][27][28]. Notably, the energetic ordering of Γ-versus K-derived valence moiré bands is sensitively dependent on material combination, twist angle, and atomic relaxation effects [29].…”

Section: Introductionmentioning

confidence: 99%

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The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

Campbell¹,

Vitale²,

Brotons‐Gisbert³

et al. 2023

Preprint

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The interplay of charge, spin, lattice, and orbital degrees of freedom leads to a wide range of emergent phenomena in strongly correlated systems. In heterobilayer transition metal dichalcogenide moiré systems, recent observations of Mott insulators and generalized Wigner crystals are well described by triangular lattice single-orbital Hubbard models based on K-valley derived moiré bands. Richer phase diagrams, mapped onto multi-orbital Hubbard models, are possible with hexagonal lattices in Γ-valley derived moiré bands and additional layer degrees of freedom. Here we report the tunable interaction between strongly correlated hole states hosted by Γ-and K-derived moiré bands in a monolayer MoSe2 / natural WSe2 bilayer device. To precisely probe the nature of the correlated states, we optically characterise the behaviour of exciton-polarons and distinguish the layer and valley degrees of freedom. We find that the honeycomb Γ-band gives rise to a chargetransfer insulator described by a two-orbital Hubbard model with inequivalent ΓA and ΓB orbitals. With an out-of-plane electric field, we re-order the ΓB-and K-derived bands energetically, driving an abrupt redistribution of carriers to the layer-polarized K orbital where new correlated states are observed. Finally, by fine-tuning the band-alignment, we obtain degeneracy of the ΓB and K orbitals at the Fermi level. In this critical condition, stable Wigner crystals with carriers distributed across the two orbitals are observed until the Fermi-level reaches one hole per lattice site, whereupon the system collapses into a filled ΓB orbital. Our results establish a platform to investigate the interplay of charge, spin, lattice, and layer geometry in multi-orbital Hubbard model Hamiltonians.

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Section: Discussionmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

Campbell¹,

Vitale²,

Brotons‐Gisbert³

et al. 2023

Preprint

View full text Add to dashboard Cite

show abstract

“…Further, in semiconducting transition metal dichalcogenide (TMD)-based moiré systems, the strengths of Coulomb interactions between particles in the moiré lattice can be continuously tuned via the moiré period 13,14 . Additionally, different real-space lattice geometries can be found in the low-energy valence moiré bands, dependent on the valley degree of freedom: moiré orbitals on a triangular lattice are generally found for K-valley moiré bands localized on a single atomic layer [13][14][15][16][17][18][19] , whereas honeycomb lattices are found for Γ-valley moiré bands spread across each layer [20][21][22][23][24][25][26][27] . In particular, the energetic ordering of Γ-versus K-derived valence moiré bands is sensitively dependent on material combination, twist angle and atomic relaxation effects 28 .…”

Section: Layer and Valley Degrees Of Freedom For Holes In Moiré Bandsmentioning

confidence: 99%

“…2c,d, black dashed lines), which we ascribe to the formation of generalized Wigner crystals that arise due to long-range Coulomb interactions 16,30,35 . Although an in-depth understanding about the specific charge and spin ordering of these states is beyond the scope of this work, we refer to recent theoretical works as a starting point to address these issues 22,[36][37][38] .…”

Section: Probing γ-Valley Correlated Electronic Statesmentioning

confidence: 99%

The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

Campbell,

Vitale,

Brotons-Gisbert

et al. 2024

Nat. Phys.

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The interplay of charge, spin, lattice and orbital degrees of freedom leads to a variety of emergent phenomena in strongly correlated systems. In transition-metal-dichalcogenide-based moiré heterostructures, recent observations of correlated phases can be described by triangular-lattice single-orbital Hubbard models based on moiré bands derived from the Brillouin-zone corners—the so-called K valleys. Richer phase diagrams described by multi-orbital Hubbard models are possible with hexagonal lattices that host moiré bands at the zone centre—called Γ valleys—or an additional layer degree of freedom. Here we report the tunable interaction between strongly correlated hole states hosted by Γ- and K-derived bands in a heterostructure of monolayer MoSe2 and bilayer 2H WSe2. We characterize the behaviour of exciton–polarons to distinguish the layer and valley degrees of freedom. The Γ band gives rise to a charge-transfer insulator described by a two-orbital Hubbard model. An out-of-plane electric field re-orders the Γ- and K-derived bands and drives the redistribution of carriers to the layer-polarized K orbital, generating Wigner crystals and Mott insulating states. Finally, we obtain degeneracy of the Γ and K orbitals at the Fermi level and observe interacting correlated states with phase transitions dependent on the doping density. Our results establish a platform to investigate multi-orbital Hubbard model Hamiltonians.

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Magnetic quasi-atomic electrons driven reversible structural and magnetic transitions between electride and its hydrides

Lee,

Lim,

Khan

et al. 2023

Nat Commun

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In electrides, interstitial anionic electrons (IAEs) in the quantized energy levels at cavities of positively charged lattice framework possess their own magnetic moment and interact with each or surrounding cations, behaving as quasi-atoms and inducing diverse magnetism. Here, we report the reversible structural and magnetic transitions by the substitution of the quasi-atomic IAEs in the ferromagnetic two-dimensional [Gd2C]2+·2e− electride with hydrogens and subsequent dehydrogenation of the canted antiferromagnetic Gd2CHy (y > 2.0). It is demonstrated that structural and magnetic transitions are strongly coupled by the presence or absence of the magnetic quasi-atomic IAEs and non-magnetic hydrogen anions in the interlayer space, which dominate exchange interactions between out-of-plane Gd−Gd atoms. Furthermore, the magnetic quasi-atomic IAEs are inherently conserved by the hydrogen desorption from the P$$\bar{3}$$ 3 ¯ 1m structured Gd2CHy, restoring the original ferromagnetic state of the R$$\bar{3}$$ 3 ¯ m structured [Gd2C]2+·2e− electride. This variable density of magnetic quasi-atomic IAEs enables the quantum manipulation of floating electron phases on the electride surface.

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Magnetic ground states of honeycomb lattice Wigner crystals

Cited by 10 publications

References 67 publications

The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

The interplay of field-tunable strongly correlated states in a multi-orbital moiré system

Magnetic quasi-atomic electrons driven reversible structural and magnetic transitions between electride and its hydrides

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