From node-line semimetals to large-gap quantum spin Hall states in a family of pentagonal group-IVA chalcogenide

Zhang, Run-Wu; Liu, Cheng-Cheng; Ma, Da-Shuai; Yao, Yugui

doi:10.1103/physrevb.97.125312

Cited by 26 publications

(16 citation statements)

References 64 publications

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“…In this respect, Young et al theoretically proposed symmetry protected 2D Dirac semimetals in which Dirac cones at high-symmetry points are not gapped by SOC [30]. On the other hand, Honeycomb-Kagome lattice Hg 3 As 2 [31], Lieb lattice BeH 2 and Be 2 C [32], single layer MX (M=Pd, Pt; X=S, Se, Te) [33], single layer B 2 C [34], 2D compounds X 2 Y (X=Ca, Sr and Ba; Y=As, Sb and Bi) [35], β 12 -borophene [36] and pentagonal group p-IVX 2 (IV=C, Si, Ge, Sn, Pb; X=S, Se, Te) [37] were predicted to be 2D node line semimetals, in which the conduction and valence bands touch near the Fermi level at extended loops. More intriguingly, single layer Cu 2 Si [38] and CuSe [39] have been experimentally demonstrated to be 2D node line semimetals.…”

Section: Introductionmentioning

confidence: 99%

Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn

Wang

Han

et al. 2019

New J. Phys.

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Realizing semimetal states in two-dimensional (2D) materials are of great importance for their future application in novel quantum devices at the nanoscale. Using first-principles calculations based on density functional theory, we propose a new 2D tetragonal allotrope of Ge and Sn, 2D T-Ge and T-Sn, which consists of repeated square and octagon rings. The calculated cohesive energy, ab initio molecular dynamic simulations and phonon dispersions indicate that 2D T-Ge and T-Sn are stable at room temperature and possibly synthesized in the experiments under appropriate growth conditions. In the absence of spin-orbital coupling (SOC), 2D T-Ge and T-Sn are node line semimetals and the nodal loop in 2D T-Ge and T-Sn are protected by the combination of the spatial inversion P and timereversal T symmetries. Remarkably, when SOC is included, 2D T-Ge and T-Sn are still node line semimetals although small gap is opened along the nodal loop, which are identified by nontrivial Z 2 invariant and topological edge states at the sample boundaries. Furthermore, our calculations show that node line semimetal states in 2D T-Ge and T-Sn are robust with the biaxial strains in the range of −3% to 3%. Our results provide a new 2D material platform for realization of 2D topological node line semimetals and innovative applications of topological node line semimetals.

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Section: Introductionmentioning

confidence: 99%

Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn

Wang

Han

et al. 2019

New J. Phys.

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“…This is because in such cases, each band have a definite parity under mirror, and the crossing between two bands with different parity will generically form a Weyl line in the 2D BZ. These lines have been found in many material examples, such as Hg 3 As 2 [70], Ca 2 As [71], PdS [72], C 9 N 4 [73], p-IVX 2 [74], and honeycomb borophene oxide [75]. This type of lines are in a sense unpinned: they are not restricted to high-symmetry paths and their shapes may be deformed under perturbation.…”

Section: D Nodal-line Tsmmentioning

confidence: 90%

Two-dimensional topological semimetals*

Feng

Zhu

et al. 2021

Chinese Phys. B

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The field of two-dimensional topological semimetals, which emerged at the intersection of twodimensional materials and topological materials, have been rapidly developing in recent years. In this article, we briefly review the progress in this field. Our focus is on the basic concepts and notions, in order to convey a coherent overview of the field. Some material examples are discussed to illustrate the concepts. We discuss the outstanding problems in the field that need to be addressed in future research.

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“…Besides transition metal dichalcogenides (TMDCs), pulsed fiber lasers have also been demonstrated with layered transition-metal monochalcogenides (TMMCs) [23]. In addition, there is still plenty of room for pentagonal 2D materials and 2D V-V binary materials, which is recently emerged and predicted with superior properties by theoretical calculations [114][115][116][117]. The LD material systems could be further enriched by stacking distinct LD materials into 2D or mixed-dimensional van der Waals heterostructures [118][119][120].…”

Section: Enrich the Materials Options Of Ld Materials In Pulsed Wavegumentioning

confidence: 99%

Low-dimensional materials as saturable absorbers for pulsed waveguide lasers

Pang

et al. 2020

J. Phys. Photonics

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Low-dimensional (LD) materials, such as 2D materials, carbon nanotubes, and nanoparticles, have attracted increasing attention for light modulation in photonics and optoelectronics. The high nonlinearity, broad bandwidth, and fast response enabled by LD materials are critical to realize desired functionalities in highly integrated photonic systems. Driven by the growing demand for compact laser sources, LD materials have recently demonstrated their great capacity as saturable absorbers in pulsed (Q-switched or mode-locked) laser generation in waveguide platforms. We review the recent advances of pulsed waveguide lasers based on LD materials. A perspective is also presented in this rapidly growing research field. Fundamentals of LD saturable absorbers and optical waveguidesOwing to the diverse electronic structures, LD materials offer versatile options to realize wide applications based on the nonlinear optical response. Currently, semiconductor saturable absorber mirrors (SESAMs) are the most frequently used commercial SAs, processing high damage threshold and prominent stability. However, a variety of LD materials retain a number of advantages to be nonlinear SAs, of which SESAMs © 2020 The Author(s). Published by IOP Publishing Ltd J. Phys. Photonics 2 (2020) 031001 Z Li et al cannot fulfill, such as broadband operation, ultrafast recovery time, low cost, and better compatibility with compact devices such as fibers and waveguides. Recently, an increasing number of research efforts have been made to unfold the nonlinear optical properties as well as its corresponding applications of the emerging LD materials [14][15][16][17][18][19][20][21][22][23]. For semiconducting or semimetallic LD materials, the main mechanism for nonlinear saturable absorption is Pauli blocking. After photoexcitation, non-equilibrium carrier state could be created, in which valence-band electrons can be excited to the conduction band, and a hole can be formed on the valence band. As the increase of the incident light intensity, the photon absorption processes of LD materials experience a transition from linear absorption to saturable absorption. When the light intensity continues increasing and reaches the saturation intensity, the extra photons will no longer be absorbed by the electrons in the valence band, and the transmittance of the SA will not increase but gradually tend to a stable value. For metallic nanoparticles, the dominant mechanism is the LSPR effect arising from the interaction between the electric field of incident light and the surface electrons in the conduction band. The optical nonlinearity could be significantly enhanced while maintaining the ultrafast recovery time. These nonlinear effects are widely used in passively Q-switched or mode-locked lasers. In order to characterize the nonlinear optical properties, femtosecond Z-scan spectroscopy is typically employed by moving the sample along the Z direction through a focused Gaussian beam. The laser intensity can be varied continuously with the maximum at the focal poin...

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From node-line semimetals to large-gap quantum spin Hall states in a family of pentagonal group-IVA chalcogenide

Cited by 26 publications

References 64 publications

Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn

Topological node line semimetal state in two-dimensional tetragonal allotrope of Ge and Sn

Two-dimensional topological semimetals*

Low-dimensional materials as saturable absorbers for pulsed waveguide lasers

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