Angle-resolved photoemission spectroscopy and its application to topological materials

Lv, Baoliang; Qian, Tian; Ding, Hong

doi:10.1038/s42254-019-0088-5

Cited by 243 publications

(142 citation statements)

References 244 publications

(810 reference statements)

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“…The theoretical predictions, which are conducted on the wave-vector-dependent band structures below E F , could be veried by high-resolution ARPES. 34 Many previous measurements have clearly identied the low-energy valence bands of layered graphene systems as being only initiated from the K/K 0 valleys, 58 such as the linear Dirac-cone structure in twisted bilayer graphene (Moire superlattices with very large unit cells) 59 & monolayer graphene, 60 the parabolic/parabolic and linear dispersions in bilayer/tri-layer AB stackings, 60,61 the linear, partially at and Sombrero-shaped bands in tri-layer ABC stacking, 61,62 and the semi-metallic property of bulk Bernal graphite. 61 These diversied electronic energy spectra are identied to only arise from the pure and unique interlayer 2p z -2p z orbital hybridizations in normal/enlarged honeycomb lattices, according to consistency between the rst-principles method 63 and the tight-binding model.…”

Section: Rich and Unique Electronic Propertiesmentioning

confidence: 99%

“…The difficulties of analysis lie in the very complicated orbital-decomposed density of states, which is supported by the electronic energy spectrum and carrier density. The theoretical predictions, which are conducted on the optimal geometry, the occupied valence state and the energy gap & whole energy spectrum, could be veried by highresolution measurements of X-ray diffraction/low-energy electron diffraction (LEED), 33 angle-resolved photoemission spectroscopy (ARPES), 34 and scanning tunneling microscopy (STM). 35…”

Section: Introductionmentioning

confidence: 99%

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Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂

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Section: Rich and Unique Electronic Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂

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“…k=2 and k=3. However, we still need to sum over m k in (16). Due to the near degeneracy of MPE states in each manifold k, we can approximate In contrast to the MI case, the off-diagonal elements are ignorable.…”

Section: Discussionmentioning

confidence: 99%

“…(16) as ( )|ˆ| ( )¯( ) The overlap of the excited state |y ñ ex with energy eigenstates | ñ  n in the MI (left) and the BI (right).…”

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confidence: 99%

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Okamoto

2019

New J. Phys.

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Motivated by the recent progress in time-resolved nonequilibrium spectroscopy in condensed matter, we study an optically excited one-dimensional ionic Hubbard model by exact diagonalization. The model is relevant to organic crystals, transition metal oxides, or ultracold atoms in optical lattices. We implement numerical pump-probe measurements to calculate time-dependent conductivity and single-particle spectral functions. In general, short optical excitation induces a metallic behavior imprinted as a Drude peak in conductivity or an in-gap density of states. In a Mott insulator, we find that the induced Drude peak oscillates at the pump frequency and its second harmonic. The former comes from the oscillation of currents, and the latter from the interference of single-and three-photon excited states. In a band insulator, the Drude peak oscillates only at the pump frequency, and quantities such as the double occupancy do not oscillate. The absence of the second harmonic oscillation is due to the degeneracy of multi-photon excited states. The in-gap density of states in both insulators correlates with the Drude weight and the energy absorption for weak pumping. Strong pumping leads to saturation of the in-gap density of states and to suppression of the Drude weight in the Mott regime. We have also checked that the above features are robust for insulators in the intermediate parameter range. Our study demonstrates the distinct natures of the multi-photon excited states in two different insulators.Alternatively, we can regard it as a variant of the Falicov-Kimball model [41] where f-electrons are chargeordered and frozen. Here we ignore the dynamics of the underlying objects that give the staggered modulation. This means that our results are relevant to experimental data for a short period of time before the ionic motion sets in; the model serves as a starting point for further investigation with dynamical phonons. There is also an experimental realization of the model in ultracold atoms [42].We employ an exact diagonalization method to solve the time-dependent Schrödinger equation, and implement numerical pump-probe measurements to obtain time-dependent conductivity [43-45] and singleparticle spectral functions [46,47]. Short optical pulses applied to a Mott insulator (MI) or a band insulator (BI) make the system metallic, which is indicated by a nonzero Drude peak in conductivity. We find that the Drude peak oscillates at the pump frequency in both cases, while also at the second harmonic in the MI. The second harmonic oscillation in the Mott regime is explained by a constructive interference of single-and three-photon excited states. We have confirmed that the distinct dynamic behaviors still appear for intermediate cases unless the energy gap becomes too small. The relation between the in-gap density of states and the Drude weight is also discussed.The paper is organized as follows. In section 2, an ionic Hubbard model is introduced. Section 3 is devoted to the details of the exact diagonalization method and pump...

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“…To date, ideal type-I Weyl points with symmetric cone spectra have been ascertained in available semimetals (e.g. NbAs, TaP, TaAs) and also in artificial photonic crystal structures [4][5][6][14][15][16]. In contrast, it was not until 2015 that the concept of type-II WSMs was theoretically proposed by studying the topological properties of WTe 2 and MoTe 2 [13,17].…”

Section: Introductionmentioning

confidence: 99%

Photonic spin Hall effect on the surfaces of type-I and type-II Weyl semimetals

et al. 2020

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Topological optics is an emerging research area in which various topological and geometrical ideas are being proposed to design and manipulate the behaviors of photons. Here, the photonic spin Hall effect on the surfaces of topological Weyl semimetal (WSM) films was studied. Our results show that the spin-dependent splitting (i.e. photonic spin Hall shifts) induced by the spin-orbit interaction is little sensitive to the tilt αt of Weyl nodes and the chemical potential μ in type-I WSM film. In contrast, photonic spin Hall shifts in both the in-plane and transverse directions present versatile dependent behaviors on the αt and μ in type-II WSM film. In particular, the largest in-plane and transverse spin Hall shifts appear at the tilts between −2 and −3, which are ~40 and ~10 times of the incident wavelength, respectively. Nevertheless, the largest spin Hall shifts for type-II WSM film with positive αt are only several times of incident wavelength. Moreover, the photonic spin Hall shifts also exhibit different variation trends with decreasing the chemical potential for different signs of αt in type-II WSM films. This dependence of photonic spin Hall shifts on tilt orientation in type-II WSM films has been explained by time-reversal-symmetry-breaking Hall conductivities in WSMs.

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Angle-resolved photoemission spectroscopy and its application to topological materials

Abstract: ARPES, angle-resolved photoemission spectroscopy. a Examples of common discharge lamps include the He lamp (with photon energies of 21.2eV for He Iα and 40.8 eV for He IIα) and the Xe lamp (with a photon energy of 8.4 eV for Xe I). b Data for the VUV5k He lamp.

Cited by 243 publications

References 244 publications

Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂

Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Photonic spin Hall effect on the surfaces of type-I and type-II Weyl semimetals

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Angle-resolved photoemission spectroscopy and its application to topological materials

Abstract: ARPES, angle-resolved photoemission spectroscopy. a Examples of common discharge lamps include the He lamp (with photon energies of 21.2eV for He Iα and 40.8 eV for He IIα) and the Xe lamp (with a photon energy of 8.4 eV for Xe I). b Data for the VUV5k He lamp.

Cited by 243 publications

References 244 publications

Featured properties of Li+-based battery anode: Li4Ti5O12

Featured properties of Li+-based battery anode: Li4Ti5O12

Time-dependent spectral properties of a photoexcited one-dimensional ionic Hubbard model: an exact diagonalization study

Photonic spin Hall effect on the surfaces of type-I and type-II Weyl semimetals

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Product

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Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂

Featured properties of Li⁺-based battery anode: Li₄Ti₅O₁₂