Niels R. Walet
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View article: Two-cluster approach to the properties of one- and two-neutron-halo nuclei
Two-cluster approach to the properties of one- and two-neutron-halo nuclei Open
In this work, we present a new approximate method for obtaining simple wave functions for the ground state of exotic nuclei with a neutron halo. We model the system as a two-cluster structure, treating the core and halo as inert objects. T…
View article: Multiphase superconductivity in PdBi2
Multiphase superconductivity in PdBi2 Open
View article: Multiphase superconductivity in PdBi2
Multiphase superconductivity in PdBi2 Open
Unconventional superconductivity, where electron pairing does not involve electron-phonon interactions, is often attributed to magnetic correlations in a material. Well known examples include high-T_c cuprates and uranium-based heavy fermi…
View article: Two-cluster approach to the properties of one- and two-neutron-halo nuclei
Two-cluster approach to the properties of one- and two-neutron-halo nuclei Open
In this work, we present a new approximate method for obtaining simple wave functions for the ground state of exotic nuclei with a neutron halo. We model the system as a two-cluster structure, treating the core and halo as inert objects. T…
View article: Extended Coupled Cluster approach to Twisted Graphene Layers
Extended Coupled Cluster approach to Twisted Graphene Layers Open
A study of correlation effects in twisted bilayer graphene is presented using the extended coupled cluster method at consistent mean-field and beyond mean-field truncations. In order to describe the phase transitions in this strongly corre…
View article: Prediction of two-neutron halos in the N = 28 isotones 40Mg and 39Na
Prediction of two-neutron halos in the N = 28 isotones 40Mg and 39Na Open
The ground states of the nuclei Mg40 and Na39 are investigated using the hyperspherical formalism. Since they are located at the edge of the “big island of inversion”, we concentrate on whether we are likely to find two-neutron Borromean h…
View article: Prediction of two-neutron halos in the $N=28$ isotones $^{40}$Mg and $^{39}$Na
Prediction of two-neutron halos in the $N=28$ isotones $^{40}$Mg and $^{39}$Na Open
The ground states of the nuclei $^{40}$Mg and $^{39}$Na are investigated using the hyperspherical formalism. Since they are located at the edge of the "big island of inversion", we concentrate on whether we are likely to find two-neutron B…
View article: Giant Atomic Swirl in Graphene Bilayers with Biaxial Heterostrain
Giant Atomic Swirl in Graphene Bilayers with Biaxial Heterostrain Open
The study of moiré engineering started with the advent of van der Waals heterostructures, in which stacking 2D layers with different lattice constants leads to a moiré pattern controlling their electronic properties. The field entered a ne…
View article: Calculation of Dynamical Response Functions Using a Bound-State Method
Calculation of Dynamical Response Functions Using a Bound-State Method Open
View article: Calculation of Dynamical Response Functions Using a Bound-state Method
Calculation of Dynamical Response Functions Using a Bound-state Method Open
We investigate a method to extract response functions (dynamical polarisabilities) directly from a bound-state approach applied to calculations of perturbation-induced reactions. The use of a square-integrable basis leads to a response in …
View article: Wannier Topology and Quadrupole Moments for a generalized Benalcazar-Bernevig-Hughes Model
Wannier Topology and Quadrupole Moments for a generalized Benalcazar-Bernevig-Hughes Model Open
We analyze a special separable and chiral-symmetric model with a quantized quadrupole moment, extending the Benalcazar-Bernevig-Hughes model [Science 357, 61 (2017)]. Using nested-Wilson loop formalism, we give an exact expression for Wann…
View article: Rotating Majorana zero modes in a disk geometry
Rotating Majorana zero modes in a disk geometry Open
We study the manipulation of Majorana zero modes in a thin disk made from a\n$p$-wave superconductor in order to understand their use as a building block\nfor topological quantum computers. We analyze the second-order topological\ncorner m…
View article: Electrostatic interactions in twisted bilayer graphene
Electrostatic interactions in twisted bilayer graphene Open
The effects of the long range electrostatic interaction in twisted bilayer graphene are described using the Hartree-Fock approximation. The results show a significant dependence of the band widths and shapes on electron filling, and the ex…
View article: Magnetization Signature of Topological Surface States in a Non‐Symmorphic Superconductor
Magnetization Signature of Topological Surface States in a Non‐Symmorphic Superconductor Open
Superconductors with nontrivial band structure topology represent a class of materials with unconventional and potentially useful properties. Recent years have seen much success in creating artificial hybrid structures exhibiting the main …
View article: Flat bands, strains, and charge distribution in twisted bilayer <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>h</mml:mi><mml:mtext>−</mml:mtext><mml:mi>BN</mml:mi></mml:math>
Flat bands, strains, and charge distribution in twisted bilayer Open
We study the effect of twisting on bilayer graphene. The effect of lattice\nrelaxation is included; we look at the electronic structure, piezo-electric\ncharges and spontaneous polarisation. We show that the electronic structure\nwithout l…
View article: Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride
Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride Open
View article: Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride
Charge-polarized interfacial superlattices in marginally twisted hexagonal boron nitride Open
When two-dimensional crystals are brought into close proximity, their interaction results in strong reconstruction of electronic spectrum and local crystal structure. Such reconstruction strongly depends on the twist angle between the two …
View article: Tunable terahertz oscillation arising from Bloch-point dynamics in chiral magnets
Tunable terahertz oscillation arising from Bloch-point dynamics in chiral magnets Open
Skyrmionic textures are being extensively investigated due to the occurrence of novel topological magnetic phenomena, and their promising applications in a new generation of spintronic devices take advantage of the robust topological stabi…
View article: Narrow bands and electrostatic interactions in graphene stacks
Narrow bands and electrostatic interactions in graphene stacks Open
Superconducting and insulating phases are well-established in twisted graphene bilayers, and they have also been reported in other arrangements of graphene layers. We investigate three such situations, (untwisted) bilayer graphene on hBN, …
View article: Twists and the Electronic Structure of Graphitic Materials
Twists and the Electronic Structure of Graphitic Materials Open
We analyze the effect of twists on the electronic structure of configurations of infinite stacks of graphene layers. We focus on three different cases: an infinite stack where each layer is rotated with respect to the previous one by a fix…
View article: The emergence of one-dimensional channels in marginal-angle twisted bilayer graphene
The emergence of one-dimensional channels in marginal-angle twisted bilayer graphene Open
We generalize the continuum model for Moir\\'e structures made from twisted\ngraphene layers, in order to include lattice relaxation and the formation of\nchannels at very small (marginal) twist angles. We show that a precise\ndescription …
View article: Electronic band structure and pinning of Fermi energy to Van Hove singularities in twisted bilayer graphene: A self-consistent approach
Electronic band structure and pinning of Fermi energy to Van Hove singularities in twisted bilayer graphene: A self-consistent approach Open
The emergence of flat bands in twisted bilayer graphene leads to an\nenhancement of interaction effects, and thus to insulating and superconducting\nphases at low temperatures, even though the exact mechanism is still widely\ndebated. The …
View article: Continuum models for twisted bilayer graphene: Effect of lattice deformation and hopping parameters
Continuum models for twisted bilayer graphene: Effect of lattice deformation and hopping parameters Open
We analyze a description of twisted graphene bilayers, that incorporates\ndeformation of the layers due to the nature modern interlayer potentials, and a\nmodification of the hopping parameters between layers in the light of the\nclassic S…
View article: Lattice Deformation, Low Energy Models and Flat Bands in Twisted Graphene Bilayers
Lattice Deformation, Low Energy Models and Flat Bands in Twisted Graphene Bilayers Open
Twisted graphene bilayers show a complex electronic structure, further modified by interaction effects. The main features can be obtained from effective models, which make use a few phenomenological parameters. We analyze the influence of …
View article: A functional renormalization group approach to thermodynamics of weakly interacting Bose gases: from linear to hydrodynamic fluctuations
A functional renormalization group approach to thermodynamics of weakly interacting Bose gases: from linear to hydrodynamic fluctuations Open
We study weakly interacting Bose gases using the functional renormalization group with a hydrodynamic effective action. We use a scale-dependent parametrization of the boson fields developed previously that interpolates between a Cartesian…
View article: Electrostatic effects, band distortions, and superconductivity in twisted graphene bilayers
Electrostatic effects, band distortions, and superconductivity in twisted graphene bilayers Open
Significance For small twist angles, bilayer graphene forms long-wavelength Moiré patterns. For specific, so-called magic, angles of the order of 1 degree, very narrow bands have been seen that lead to superconductivity. The underlying mec…
View article: Application of the functional renormalization group to Bose gases: From linear to hydrodynamic fluctuations
Application of the functional renormalization group to Bose gases: From linear to hydrodynamic fluctuations Open
We study weakly interacting Bose gases using the functional renormalization group with a hydrodynamic effective action. We use a scale-dependent parametrization of the boson fields that interpolates between a Cartesian representation at hi…
View article: Electrostatic effects and band distortions in twisted graphene bilayers
Electrostatic effects and band distortions in twisted graphene bilayers Open
View article: Effect of layered water structures on the anomalous transport through nanoscale graphene channels
Effect of layered water structures on the anomalous transport through nanoscale graphene channels Open
We analyse the enhanced flow rate of water through nano-fabricated graphene channels that has been recently observed experimentally. Using molecular dynamics simulations in channels of similar lateral dimensions as the experimental ones, o…
View article: Edge Modes and Nonlocal Conductance in Graphene Superlattices
Edge Modes and Nonlocal Conductance in Graphene Superlattices Open
We study the existence of edge modes in gapped moiré superlattices of graphene monolayer ribbons on a hexagonal boron nitride substrate. We find that the superlattice bands acquire finite Chern numbers, which lead to a valley Hall effect. …