Ising and XY paramagnons in two-dimensional 
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Costa, A. T.; Costa, Marcio; Fernández-Rossier, J.

doi:10.1103/physrevb.105.224412

Cited by 5 publications

(1 citation statement)

References 48 publications

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“…Because of that, the valence and conduction band states in the neighborhood of the K and K points are mostly localized in the A and B sublattices, respectively. Now, if we add the SOC term, the otherwise spin-degenerate bands split into two spin-polarized bands [37]. Due to time-reversal symmetry, Krammer's doublets have opposite spin and momentum.…”

Section: A Kane-mele Modelmentioning

confidence: 99%

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Losada,

Costa,

Biel

et al. 2023

Phys. Rev. B

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We study indirect exchange interactions between localized spins of magnetic impurities in spin valley coupled systems described with the Kane-Mele model. Our model captures the main ingredients of the energy bands of the 1H transition metal dichalcogenide (TMD) monolayers, such as 1H -MoS 2 and 1H -NbSe 2 . To obtain the effective interactions, we use the exact diagonalization of the Hamiltonian, avoiding momentum cutoffs. We start by comparing the standard perturbation expansion in terms of the Kondo exchange with the exact calculation of the interaction, treating the local spins classically. We find that perturbation theory works well even beyond the regime where the relevant figure of merit, the ratio between the exchange J and the hopping t, is small. We verify that the effective indirect exchange Hamiltonian derived from perturbation theory also works in the nonperturbative regime. Additionally, we analyze the interplay between the symmetry of the different terms of the interaction (Heisenberg, Ising, and Dzyaloshinskii-Moriya), the Fermi-surface topology, and the crystallographic direction in which the impurities are placed. We show that the indirect exchange along the armchair direction is actually Heisenberg-like, due to the reflection symmetry of the crystal structure around this direction. Finally, we explore the exploitation of indirect exchange, combined with atomic manipulation, to engineer the Majumdar-Ghosh model. Our results show that TMDs provide an extremely versatile platform to engineer indirect exchange interactions.

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Section: A Kane-mele Modelmentioning

confidence: 99%

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Losada,

Costa,

Biel

et al. 2023

Phys. Rev. B

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Anisotropic Spin Fluctuations Induced by Spin‐Orbit Coupling in a Misfit Layer Compound (LaSe)_1.14(NbSe₂)

Shan,

Li,

Yang

et al. 2024

Advanced Science

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Spin‐orbit coupling (SOC) has significant effects on the superconductivity and magnetism of transition metal dichalcogenides (TMDs) at the 2D limit. Although 2D TMD samples possess many exotic properties different from those of bulk samples, experimental characterization in this field is still limited, especially for magnetism. Recent studies have revealed that bulk misfit layer compounds (MLCs) with (LaSe)1.14(NbSe2)n = 1,2 exhibit an Ising superconductivity similar to that of heavily electron‐doped NbSe2 monolayers. This offers an opportunity to study the effect of SOC on the magnetism of 2D TMDs. Here, the possible SOC effect in (LaSe)1.14(NbSe2) is investigated by measuring nuclear magnetic resonance (NMR) and electrical transport. It is found that the LaSe layer not only functions as a charge reservoir for transferring electrons into the NbSe2 layer but also remarkably influences the local electronic environment around the 93Nb nuclei. More importantly, the significant SOC induces both a weak antilocalization (WAL) effect and anisotropic spin fluctuations in noncentrosymmetric NbSe2 layers. The present work contributes to a deep understanding of the role of the SOC effect in 2D TMDs and supports MCLs as an intriguing platform for exploring exotic physical properties within the 2D limit.

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Evidence for ground state coherence in a two-dimensional Kondo lattice

Wan,

Harsh,

Meninno

et al. 2023

Nat Commun

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Kondo lattices are ideal testbeds for the exploration of heavy-fermion quantum phases of matter. While our understanding of Kondo lattices has traditionally relied on complex bulk f-electron systems, transition metal dichalcogenide heterobilayers have recently emerged as simple, accessible and tunable 2D Kondo lattice platforms where, however, their ground state remains to be established. Here we present evidence of a coherent ground state in the 1T/1H-TaSe2 heterobilayer by means of scanning tunneling microscopy/spectroscopy at 340 mK. Our measurements reveal the existence of two symmetric electronic resonances around the Fermi energy, a hallmark of coherence in the spin lattice. Spectroscopic imaging locates both resonances at the central Ta atom of the charge density wave of the 1T phase, where the localized magnetic moment is held. Furthermore, the evolution of the electronic structure with the magnetic field reveals a non-linear increase of the energy separation between the electronic resonances. Aided by ab initio and auxiliary-fermion mean-field calculations, we demonstrate that this behavior is inconsistent with a fully screened Kondo lattice, and suggests a ground state with magnetic order mediated by conduction electrons. The manifestation of magnetic coherence in TMD-based 2D Kondo lattices enables the exploration of magnetic quantum criticality, Kondo breakdown transitions and unconventional superconductivity in the strict two-dimensional limit.

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Ising and XY paramagnons in two-dimensional 2H−NbSe2

Cited by 5 publications

References 48 publications

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Anisotropic Spin Fluctuations Induced by Spin‐Orbit Coupling in a Misfit Layer Compound (LaSe)_1.14(NbSe₂)

Evidence for ground state coherence in a two-dimensional Kondo lattice

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Ising and XY paramagnons in two-dimensional 2H−NbSe2

Cited by 5 publications

References 48 publications

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Nonperturbative indirect exchange in spin valley coupled two-dimensional crystals

Anisotropic Spin Fluctuations Induced by Spin‐Orbit Coupling in a Misfit Layer Compound (LaSe)1.14(NbSe2)

Evidence for ground state coherence in a two-dimensional Kondo lattice

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Resources

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Anisotropic Spin Fluctuations Induced by Spin‐Orbit Coupling in a Misfit Layer Compound (LaSe)_1.14(NbSe₂)