Topological insulators and superconductors

Qi, Xiao Liang; Zhang, Shou Cheng

doi:10.1103/revmodphys.83.1057

Cited by 13,460 publications

(13,545 citation statements)

References 325 publications

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“…1 and Supplementary Note 1). We observe maximum conductance values close to e 2 /h (E0.9e 2 Fig. 3c may not show all the alternating phases of the AB oscillations; however, the overall dependence of the magnetoconductance on gate voltage is qualitatively consistent with theoretical expectations 10,11 .…”

Section: Aharonov-bohm Oscillations As a Function Of Fermi Energysupporting

confidence: 84%

“…I n three-dimensional topological insulator (3D TI) nanowires, charge transport occurs via gapless surface states where the spin is fixed perpendicular to the momentum [1][2][3][4][5][6] . When a magnetic field (B) is applied along the nanowire axis, the surface electrons encircling the wire pick up a phase of 2pF/F 0 , where F ¼ BS is the magnetic flux through cross-sectional area S and F 0 ¼ h/e is the magnetic flux quantum, where h is Planck's constant and e the electron charge.…”

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confidence: 99%

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Aharonov–Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire

et al. 2015

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Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi 1.33 Sb 0.67 )Se 3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications.

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Section: Aharonov-bohm Oscillations As a Function Of Fermi Energysupporting

confidence: 84%

mentioning

confidence: 99%

Aharonov–Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire

et al. 2015

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“…Topological insulators (TIs), [1][2][3][4][5][6][7] as a new class of quantum materials, hold great potential for applications in quantum information, spintronics, field effect transistors, as well as thermoelectrics. [8][9][10][11][12][13][14] The most interesting character of TIs is the presence of robust topological Dirac surface states in three-dimensional (3D) TIs or helical edge states in two-dimensional (2D) TIs with spin locked to momentum as protected by time-reversal symmetry.…”

Section: Introductionmentioning

confidence: 99%

Room Temperature Quantum Spin Hall Insulators with a Buckled Square Lattice

2015

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Two-dimensional (2D) topological insulators (TIs), also known as quantum spin Hall (QSH) insulators, are excellent candidates for coherent spin transport related applications because the edge states of 2D TIs are robust against nonmagnetic impurities since the only available backscattering channel is forbidden.Currently, most known 2D TIs are based on a hexagonal (specifically, honeycomb) lattice. Here, we propose that there exists the quantum spin Hall effect (QSHE) in a buckled square lattice. Through performing global structure optimization, we predict a new three-layer quasi-2D (Q2D) structure which has the lowest energy among all structures with the thickness less than 6.0 Å for the BiF system. It is identified to be a Q2D TI with a large band gap (0.69 eV). The electronic states of the Q2D BiF system near the Fermi level are mainly contributed by the middle Bi square lattice, which are sandwiched by two inert BiF 2 layers. This is beneficial since the interaction between a substrate and the Q2D material may not change the topological properties of the system, as we demonstrate in the case of the NaF substrate. Finally, we come up with a new tight-binding model for a two-orbital system with the buckled square lattice to explain the low-energy physics of the Q2D BiF material. Our study not only predicts a QSH insulator for realistic room temperature applications, but also provides a new lattice system for engineering topological states such as quantum anomalous Hall effect.

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“…The discovery of the integer and fractional quantum Hall effects in the 1980s has led to a new paradigm, where quantum phases of matter are characterized by the topology of their ground-state wavefunctions. Since then, topological phases have been identified in physical systems ranging from condensed-matter [2][3][4][5][6][7][8][9] and high-energy physics 10 to quantum optics 11 and atomic physics [12][13][14][15] .…”

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confidence: 99%

Observation of topologically protected bound states in photonic quantum walks

et al. 2012

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Topological phases exhibit some of the most striking phenomena in modern physics. much of the rich behaviour of quantum Hall systems, topological insulators, and topological superconductors can be traced to the existence of robust bound states at interfaces between different topological phases. This robustness has applications in metrology and holds promise for future uses in quantum computing. Engineered quantum systems-notably in photonics, where wavefunctions can be observed directly-provide versatile platforms for creating and probing a variety of topological phases. Here we use photonic quantum walks to observe bound states between systems with different bulk topological properties and demonstrate their robustness to perturbations-a signature of topological protection. Although such bound states are usually discussed for static (time-independent) systems, here we demonstrate their existence in an explicitly time-dependent situation. moreover, we discover a new phenomenon: a topologically protected pair of bound states unique to periodically driven systems.

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Topological insulators and superconductors

Cited by 13,460 publications

References 325 publications

Aharonov–Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire

Aharonov–Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire

Room Temperature Quantum Spin Hall Insulators with a Buckled Square Lattice

Observation of topologically protected bound states in photonic quantum walks

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