Pseudospin-dependent Acoustic Topological Insulator by Sonic Crystals With Same Hexagonal Rods

We report the experimental and numerical realization of a pseudospin-dependent acoustic topological insulator based on two sonic crystals constructed by the same regular hexagonal rods. Based on the zone folding mechanism, we obtain double Dirac cones with a four-fold deterministic degeneracy in the sonic crystal, and realize a band inversion and topological phase transition by rotating the rods. We observe the topologically protected one-way sound propagation of pseudospin-dependent edge states in a designed topological insulator composed of two selected sonic crystals with different rotation angles of the rods. Furthermore, we experimentally demonstrate the robustness of topological sound propagation against two types of defects, in which the edge states are almost immune to backscattering, and remain pseudospin-dependent characteristics. Our work provides a diverse route for designing tunable topological functional sound devices.

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Transformation of the Topological Phase and the Edge Modes of Double-Bilayer Bismuthene with Inter-Bilayer Spacing

Crystals ◽

10.3390/cryst9050266 ◽

2019 ◽

Vol 9 (5) ◽

pp. 266 ◽

Cited By ~ 1

Author(s):

Huanzhi Hu ◽

Zhibin Shi ◽

Peng Wang ◽

Weiping Zhou ◽

Tai-Chang Chiang ◽

...

Keyword(s):

Phase Transition ◽

Valence Band ◽

Conduction Band ◽

Topological Insulator ◽

First Principles ◽

Topological Phase ◽

First Principles Calculations ◽

Topological Phase Transition ◽

Band Inversion ◽

Band Insulator

The transformations of the topological phase and the edge modes of a double-bilayer bismuthene were investigated with first-principles calculations and Green’s function as the inter-bilayer spacing increased from 0 Å to 10 Å. At a critical spacing of 2 Å, a topological phase transition from a topological insulator to a band insulator resulting from a band inversion between the highest valence band and the second lowest conduction band, was observed, and this was understood based on the particular orbital characters of the band inversion involved states. The edge modes of double-bilayer bismuthene survived the phase transition. When d was 2 Å < d < 4 Å, the interaction between the edge modes of two separated bismuthene bilayers induced an anti-crossing gap and resulted in a trivial band connection. At and beyond 4 Å, the two bilayers behavior decoupled entirely. The results demonstrate the transformability of the topological phase and the edge modes with the inter-bilayer spacing in double-bilayer bismuthene, which may be useful for spintronic applications.

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Topological phase transition between a normal insulator and a topological metal state in a quasi-one-dimensional system

Scientific Reports ◽

10.1038/s41598-021-92390-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Milad Jangjan ◽

Mir Vahid Hosseini

Keyword(s):

Phase Transition ◽

Dimensional System ◽

Inversion Symmetry ◽

Topological Phase ◽

Edge States ◽

Zero Energy ◽

One Dimensional ◽

Topological Phase Transition ◽

Metal State ◽

Topological Metal

AbstractWe theoretically report the finding of a new kind of topological phase transition between a normal insulator and a topological metal state where the closing-reopening of bandgap is accompanied by passing the Fermi level through an additional band. The resulting nontrivial topological metal phase is characterized by stable zero-energy localized edge states that exist within the full gapless bulk states. Such states living on a quasi-one-dimensional system with three sublattices per unit cell are protected by hidden inversion symmetry. While other required symmetries such as chiral, particle-hole, or full inversion symmetry are absent in the system.

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Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

10.20944/preprints201901.0295.v1 ◽

2019 ◽

Author(s):

Maksim Zholudev ◽

Aleksandr Kadykov ◽

Mikhail Fadeev ◽

Michal Marcinkiewicz ◽

Sandra Ruffenach ◽

...

Keyword(s):

Magnetic Field ◽

Phase Transition ◽

Quantum Wells ◽

Topological Insulator ◽

Critical Magnetic Field ◽

Topological Phase ◽

Temperature Dependent ◽

Transition Parameter ◽

Topological Phase Transition ◽

Band Insulator

We report on comparison between temperature-dependent magneto¬absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of detection of phase transition between topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet magnetotransport method is shown to have advantages for clear manifestation of the phase transition with accurate quantitative values of transition parameter (i.e. critical magnetic field Bc).

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Parametric Study on Rectangular Sonic Crystal

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.152-154.281 ◽

2012 ◽

Vol 152-154 ◽

pp. 281-286 ◽

Cited By ~ 5

Author(s):

Arpan Gupta ◽

Kian Meng Lim ◽

Chye Heng Chew

Keyword(s):

Band Gap ◽

Periodic Structure ◽

Parametric Study ◽

Sound Propagation ◽

Periodic Structures ◽

Sound Attenuation ◽

Experimental Results ◽

Center Frequency ◽

Sonic Crystal ◽

Sonic Crystals

Sonic crystals are periodic structures made of sound hard scatterers which attenuate sound in a range of frequencies. For an infinite periodic structure, this range of frequencies is known as band gap, and is determined by the geometric arrangement of the scatterers. In this paper, a parametric study on rectangular sonic crystal is presented. It is found that geometric spacing between the scatterers in the direction of sound propagation affects the center frequency of the band gap. Reducing the geometric spacing between the scatterers in the direction perpendicular to the sound propagation helps in better sound attenuation. Such rectangular arrangement of scatterers gives better sound attenuation than the regular square arrangement of scatterers. The model for parametric study is also supported by some experimental results.

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Acoustic topological phase transition induced by band inversion of high-order compound modes and robust pseudospin-dependent transport

Chinese Physics B ◽

10.1088/1674-1056/abad21 ◽

2020 ◽

Vol 29 (10) ◽

pp. 106301

Author(s):

Yan Li ◽

Yi-Nuo Liu ◽

Xia Zhang

Keyword(s):

Phase Transition ◽

High Order ◽

Topological Phase ◽

Topological Phase Transition ◽

Band Inversion ◽

Dependent Transport

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Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

Condensed Matter ◽

10.3390/condmat4010027 ◽

2019 ◽

Vol 4 (1) ◽

pp. 27 ◽

Cited By ~ 1

Author(s):

Maksim S. Zholudev ◽

Aleksandr M. Kadykov ◽

Mikhail A. Fadeev ◽

Michal Marcinkiewicz ◽

Sandra Ruffenach ◽

...

Keyword(s):

Magnetic Field ◽

Phase Transition ◽

Quantum Wells ◽

Topological Insulator ◽

Critical Magnetic Field ◽

Topological Phase ◽

Temperature Dependent ◽

Transition Parameter ◽

Topological Phase Transition ◽

Band Insulator

We report on the comparison between temperature-dependent magneto-absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of the detection of the phase transition between the topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet the magnetotransport method is shown to have advantages for the clear manifestation of the phase transition with accurate quantitative values of the transition parameter (i.e., critical magnetic field Bc).

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Persistent Ferromagnetism and Topological Phase Transition at the Interface of a Superconductor and a Topological Insulator

Physical Review Letters ◽

10.1103/physrevlett.113.266806 ◽

2014 ◽

Vol 113 (26) ◽

Cited By ~ 11

Author(s):

Wei Qin ◽

Zhenyu Zhang

Keyword(s):

Phase Transition ◽

Topological Insulator ◽

Topological Phase ◽

Topological Phase Transition

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Topological Phase Transition and Texture Inversion in a Tunable Topological Insulator

Science ◽

10.1126/science.1201607 ◽

2011 ◽

Vol 332 (6029) ◽

pp. 560-564 ◽

Cited By ~ 328

Author(s):

S.-Y. Xu ◽

Y. Xia ◽

L. A. Wray ◽

S. Jia ◽

F. Meier ◽

...

Keyword(s):

Phase Transition ◽

Topological Insulator ◽

Topological Phase ◽

Topological Phase Transition

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Emergent Helical Edge States in a Hybridized Three-Dimensional Topological Insulator

10.21203/rs.3.rs-519444/v1 ◽

2021 ◽

Author(s):

Su Kong Chong ◽

Lizhe Liu ◽

Kenji Watanabe ◽

Takashi Taniguchi ◽

Taylor Sparks ◽

...

Keyword(s):

Topological Insulator ◽

Quantum Tunneling ◽

Three Dimensional ◽

Quantum Spin ◽

Topological Phase ◽

Edge States ◽

Experimental Realization ◽

Transition Mechanism ◽

Topological Quantum ◽

Topological State

Abstract As the thickness of a three-dimensional (3D) topological insulator (TI) becomes comparable to the penetration depth of surface states, quantum tunneling between surfaces turns their gapless Dirac electronic structure into a gapped spectrum. Whether the surface hybridization gap can host topological edge states is still an open question. Herein, we provide transport evidence of 2D topological states in the quantum tunneling regime of a bulk insulating 3D TI BiSbTeSe2. Different from its trivial insulating phase, this 2D topological state exhibits a finite longitudinal conductance at ~2e2/h when the Fermi level is aligned within the surface gap, indicating an emergent quantum spin Hall (QSH) state. The transition from the QSH to quantum Hall (QH) state in a transverse magnetic field further supports the existence of this distinguished 2D topological phase. In addition, we demonstrate a second route to realize the 2D topological state via surface gap-closing and topological phase transition mechanism mediated by a transverse electric field. The experimental realization of the 2D topological phase in a 3D TI enriches its phase diagram and marks an important step toward functional topological quantum devices.

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