Probing the interlayer coupling in 
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 via soft x-ray angle-resolved photoemission spectroscopy

Huang, D.; Nakamura, Hiroyuki; Küster, Kathrin; Wedig, Ulrich; Schröter, Niels B. M.; Strocov, Vladimir N.; Starke, Ulrich; Takagi, H.

doi:10.1103/physrevb.105.245145

Cited by 8 publications

(2 citation statements)

References 66 publications

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“…The energy band structure of SPO examined in earlier theoretical studies reveals a reversal of the Sr‐ 4d‐ and Pb‐ 6p ‐dominated bands below and above the Fermi energy, respectively. [ 16 ] This gives rise to six band crossings along the X–Γ k‐path due to strong hybridization of the Sr‐ 4d and Pb‐ 6p orbitals and SOC. Klintenberg et al, [ 17 ] Hsieh et al, [ 18 ] and Chiu et al [ 19 ] carried out detailed density functional theory (DFT)‐based studies on the A 3 PbO systems which show that the electronic band structure of SPO is dominated by SOC and the TI nature is protected by cubic point group symmetries.…”

Section: Introductionmentioning

confidence: 99%

Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Bilal,

Alay-e-Abbas,

Abbas

et al. 2023

Physica Status Solidi (b)

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The emergence of robust surface electronic states in topological insulators such as bulk Sr3PbO inverse‐perovskite makes them suitable candidates for spintronic devices and solid‐state quantum computers. Herein, the atomic structure, surface energetics, and electronic properties of Sr3PbO inverse‐perovskite Sr2O (SO)‐terminated and SrPb‐terminated (001) surfaces are examined using density functional theory. A comparison of the computed structural properties of SO‐termianted and SrPb‐terminated (001) surfaces reveals maximum surface rumpling and changes in interlayer distances for the SrPb‐terminated surface of Sr3PbO. However, the calculated surface energies indicate that both SO‐termianted and SrPb‐terminated (001) surfaces of Sr3PbO are energetically feasible, indicating that these surfaces can coexist in a polycrystalline sample of this material. Due to the presence of Pb in Sr3PbO, a comprehensive examination of the electronic structure of bulk and supercell slab structures of Sr3PbO by taking spin–orbit coupling effects into consideration is conducted. Noninsulating nature of electronic structure for the two possible (001) terminations of Sr3PbO is found. The domination of Pb‐6p states at the Fermi energy and the hole screening observed at the SrPb‐terminated surface of Sr3PbO support the p‐type nature observed in the experiment.

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Section: Introductionmentioning

confidence: 99%

Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Bilal,

Alay-e-Abbas,

Abbas

et al. 2023

Physica Status Solidi (b)

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“…The optical band gap of monolayer NbSe 2 flakes was reported to be around ∼1.3 eV. 50 As the thickness increases, the band gap of NbSe 2 would decrease due to the interlayer coupling effect, 51 which would induce a considerable reabsorption effect of the SH signal and underestimates the second-order nonlinear optical response of the few-layer NbSe 2 flakes. In consideration of the linear absorption effect of the SH signal, the inherent second-order nonlinear susceptibility of the monolayer counterpart could be estimated as d eff inh = d eff exp / Q abs , where d eff exp is the experimentally measured effective second-order nonlinear susceptibility of odd-layered flakes and Q abs stands for the absorption of the measured few-layer sample.…”

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confidence: 99%

Observation of Anisotropic Second Harmonic Generation in Two-Dimensional Niobium Diselenide

Younus,

Zhou,

Zhu

et al. 2024

J. Phys. Chem. Lett.

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The intrinsic anisotropy of NbSe 2 provides a favorable prerequisite of second harmonic generation (SHG) and rich possibilities for tailoring its nonlinear optical (NLO) properties. Here we report the highly efficient SHG of mechanically exfoliated NbSe 2 flakes. The nonlinear optical response changes with excitation wavelengths, layer thicknesses, and polarizations of the excitation laser. The anisotropic SHG response further exhibits the intrinsic non-centrosymmetric crystal structure and could effectively assign the crystalline orientation of NbSe 2 flakes. Interestingly, although NbSe 2 flakes with tens of nanometers thickness experience attenuations in SHG performance, more efficient SHG anisotropy ratios were obtained, which are around 4 times higher than that of the 5-layer counterpart. The determined second-order nonlinearities of NbSe 2 flakes (monolayer: ∼1.0 × 10 3 pm/V; 3-layer: ∼73 pm/V) are comparable to those of the commonly reported two-dimensional materials (e.g., MoS 2 , WSe 2 , graphene) with the same number of layers and much higher than those of commercial nonlinear optical crystals.

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Theoretical Prediction of Semiconductor-Free Negative Differential Resistance Tunnel Diodes with High Peak-to-Valley Current Ratios Based on Two-Dimensional Cold Metals

Şaşıoğlu

Mertig

2023

ACS Appl. Nano Mater.

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The negative differential resistance (NDR) tunnel diodes are promising alternative devices for beyond-CMOS (complementary metal oxide semiconductor) computing because they offer several potential applications when integrated with transistors. We propose a semiconductor-free NDR tunnel diode concept that exhibits an ultrahigh peak-to-valley current ratio (PVCR) value. Our proposed NDR diode consists of two cold metal electrodes separated by a thin insulating tunnel barrier. The NDR effect stems from the unique electronic band structure of the cold metal electrodes; i.e., the width of the isolated metallic bands around the Fermi level as well as the energy gaps separating higher- and lower-lying bands determine the current–voltage (I–V) characteristics and the PVCR value of the tunnel diode. By proper choice of the cold metal electrode materials, either a conventional N-type or Λ-type NDR effect can be obtained. Two-dimensional (2D) nanomaterials offer a unique platform for the realization of proposed NDR tunnel diodes. To demonstrate the proof of concept, we employ the nonequilibrium Green function method combined with density functional theory to calculate the I–V characteristic of the lateral (AlI2/MgI2/AlI2) and vertical (NbS2/h-BN/NbS2) heterojunction tunnel diodes based on 2D cold metals. For the lateral tunnel diode, we obtain a Λ-type NDR effect with an ultrahigh PVCR value of 1016 at room temperature, while the vertical tunnel diode exhibits a conventional N-type NDR effect with a smaller PVCR value of about 104. The proposed concept provides a semiconductor-free solution for NDR devices to achieve the desired I–V characteristics with ultrahigh PVCR values for memory and logic applications.

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Probing the interlayer coupling in 2H−NbS2 via soft x-ray angle-resolved photoemission spectroscopy

Cited by 8 publications

References 66 publications

Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Observation of Anisotropic Second Harmonic Generation in Two-Dimensional Niobium Diselenide

Theoretical Prediction of Semiconductor-Free Negative Differential Resistance Tunnel Diodes with High Peak-to-Valley Current Ratios Based on Two-Dimensional Cold Metals

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Probing the interlayer coupling in 2H−NbS2 via soft x-ray angle-resolved photoemission spectroscopy

Cited by 8 publications

References 66 publications

Elucidating the Surface Properties of Sr3PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Elucidating the Surface Properties of Sr3PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Observation of Anisotropic Second Harmonic Generation in Two-Dimensional Niobium Diselenide

Theoretical Prediction of Semiconductor-Free Negative Differential Resistance Tunnel Diodes with High Peak-to-Valley Current Ratios Based on Two-Dimensional Cold Metals

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Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study

Elucidating the Surface Properties of Sr₃PbO Inverse‐Perovskite Topological Insulator: A First‐Principles Study