Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have protected conducting states on their edge or surface. These states are possible due to the combination of spin-orbit interactions and time-reversal symmetry. The two-dimensional (2D) topological insulator is a quantum spin Hall insulator, which is a close cousin of the integer quantum Hall state. A three-dimensional (3D) topological insulator supports novel spin-polarized 2D Dirac fermions on its surface. In this Colloquium the theoretical foundation for topological insulators and superconductors is reviewed and recent experiments are described in which the signatures of topological insulators have been observed. Transport experiments on $\mathrm{Hg}\mathrm{Te}∕\mathrm{Cd}\mathrm{Te}$ quantum wells are described that demonstrate the existence of the edge states predicted for the quantum spin Hall insulator. Experiments on ${\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}$, ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}$, and ${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ are then discussed that establish these materials as 3D topological insulators and directly probe the topology of their surface states. Exotic states are described that can occur at the surface of a 3D topological insulator due to an induced energy gap. A magnetic gap leads to a novel quantum Hall state that gives rise to a topological magnetoelectric effect. A superconducting energy gap leads to a state that supports Majorana fermions and may provide a new venue for realizing proposals for topological quantum computation. Prospects for observing these exotic states are also discussed, as well as other potential device applications of topological insulators.

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Colloquium: Topological insulators

We develop a unified framework to classify topological defects in insulators and superconductors described by spatially modulated Bloch and Bogoliubov de Gennes Hamiltonians. We consider Hamiltonians $\mathcal{H}(\mathbf{k},\mathbf{r})$ that vary slowly with adiabatic parameters $\mathbf{r}$ surrounding the defect and belong to any of the ten symmetry classes defined by time-reversal symmetry and particle-hole symmetry. The topological classes for such defects are identified and explicit formulas for the topological invariants are presented. We introduce a generalization of the bulk-boundary correspondence that relates the topological classes to defect Hamiltonians to the presence of protected gapless modes at the defect. Many examples of line and point defects in three-dimensional systems will be discussed. These can host one dimensional chiral Dirac fermions, helical Dirac fermions, chiral Majorana fermions, and helical Majorana fermions, as well as zero-dimensional chiral and Majorana zero modes. This approach can also be used to classify temporal pumping cycles, such as the Thouless charge pump, as well as a fermion parity pump, which is related to the Ising non-Abelian statistics of defects that support Majorana zero modes.

/pdf/topological-defects-and-gapless-modes-in-insulators-and-4ldu42oypj.pdf

Topological Defects and Gapless Modes in Insulators and Superconductors

We introduce an expression for the ${\mathbb{Z}}_{2}$ topological invariant of band insulators using the non-Abelian Berry connection. Our expression can identify the topological nature of a general band insulator without any of the gauge-fixing problems that plague the concrete implementation of previous invariants. This expression can be derived from the ``partner switching'' of the Wannier function center during time-reversal pumping and is thus equivalent to the ${Z}_{2}$ topological invariant proposed by Kane and Mele. Using our expression, we have recalculated the ${Z}_{2}$ topological index for several topological insulator material systems and obtained consistent results with the previous studies.

Equivalent expression of Z 2 topological invariant for band insulators using the non-Abelian Berry connection

Topological insulators in three dimensions are nonmagnetic insulators that possess metallic surface states (SSs) as a consequence of the nontrivial topology of electronic wavefunctions in the bulk of the material. They are the first known examples of topological order in bulk solids. We review the basic phenomena and experimental history, starting with the observation of topological insulator behavior in BixSb1−x by angle and spin-resolved photoemission spectroscopy (spin-ARPES) and continuing through measurements on other materials and by other probes. A self-contained introduction to the single-particle theory is then given, followed by the many-particle definition of a topological insulator as a material with quantized magnetoelectric polarizability. The last section reviews recent work on strongly correlated topological insulators and new effects that arise from the proximity effect between a topological insulator and a superconductor. Although this article is not intended to be a comprehensive review...

pdf/three-dimensional-topological-insulators-4zbs9ij9hw.pdf

Three-Dimensional Topological Insulators

havebeen studied. A comprehensive analysis of Shubnikov de Haas oscillations, Hall eﬀect, and opticalreﬂectivity indicates that the measured electrical transport can be attributed solely to bulk states,even at 50 mK at low Landau level ﬁlling factor, and in the quantum limit. The absence of asigniﬁcant surface contribution to bulk conduction demonstrates that even in very clean samples,the surface mobility is lower than that of the bulk, despite its topological protection.

/pdf/strong-surface-scattering-in-ultrahigh-mobility-bi2se3-3ks8bpl9v7.pdf

Strong surface scattering in ultrahigh mobility Bi2Se3 topological insulator crystals

Nuclear fusion is one of the most attractive alternatives to carbon-dependent energy sources1. Harnessing energy from nuclear fusion in a large reactor scale, however, still presents many scientific challenges despite the many years of research and steady advances in magnetic confinement approaches. State-of-the-art magnetic fusion devices cannot yet achieve a sustainable fusion performance, which requires a high temperature above 100 million kelvin and sufficient control of instabilities to ensure steady-state operation on the order of tens of seconds2,3. Here we report experiments at the Korea Superconducting Tokamak Advanced Research4 device producing a plasma fusion regime that satisfies most of the above requirements: thanks to abundant fast ions stabilizing the core plasma turbulence, we generate plasmas at a temperature of 100 million kelvin lasting up to 20 seconds without plasma edge instabilities or impurity accumulation. A low plasma density combined with a moderate input power for operation is key to establishing this regime by preserving a high fraction of fast ions. This regime is rarely subject to disruption and can be sustained reliably even without a sophisticated control, and thus represents a promising path towards commercial fusion reactors. A magnetic confinement regime established at the Korea Superconducting Tokamak Advanced Research device enables the generation of plasmas over 108 kelvin for 20 seconds with the aid of fast ions without plasma edge instabilities or impurity accumulation. 

/pdf/a-sustained-high-temperature-fusion-plasma-regime-1h0hw989.pdf

A sustained high-temperature fusion plasma regime facilitated by fast ions

The discovery of ferroelectrics induced by peculiar magnetic structures brought about extensive theoretical and experimental studies. The key driving force for these magnetic ferroelectrics appears to lie in the inverse Dzyaloshinskii-Moriya (DM) interaction in magnets with long-wavelength ``noncollinear'' spin structures. In this Brief Report, we report the magnetodielectric effect in dysprosium iron garnet which has a noncollinear spin structure within a single unit cell, through the same DM interaction. The distinct effects of magnetism on the lattice are also demonstrated by the unprecedented magnetostriction with a negative Poisson ratio. We attribute the observed magnetodielectric effects and the huge magnetostriction to the magnetic-field-induced spin reorientation from noncollinear to collinear, which possibly weakens the proposed antiferroelectric-type lattice distortion. Our results suggest an additional class of magnetodielectrics and enrich the theoretical understanding of phenomena related to peculiar magnetic structures.

Magnetodielectric effect via a noncollinear-to-collinear spin reorientation in rare-earth iron garnets

/pdf/arpes-studies-on-metal-insulator-transition-in-nis-2-x-se-x-4jpxprxdwy.pdf

ARPES studies on metal-insulator-transition in NiS$_{2-x}$Se$_{x}$

A kit for monitoring, diagnosing and screening breast cancer is provided to confirm the difference of marker protein expression from normal person and breast cancer patient and enables early diagnosis, screening and process evaluation A kit for monitoring, diagnosing and screening breast cancer comprises an antibody which is specific to a protein selected from Vitronectin, sVCAM-1(Soluble Vascular cell adhesion molecule-1), sCD40L(Soluble CD40 ligand), EGF(Epidermal growth factor), tPAI-1(Total plasminogen activator inhibitor-1), ApoA-1(Apolipoprotein-A1), proApoA-1(Proapolipoprotein-A1), Kininogen, VDBP(Vitamin D-binding protein), ApoA1/proApoA1, CRP/Kininogen, Hemoglobin, and MPO(myeloperoxidase) The kit also comprises an antibody which is specific to the combination of two or more proteins selected from D-Dimer, Vitronectin, sVCAM-1(Soluble Vascular cell adhesion molecule-1), sCD40L(Soluble CD40 ligand), EGF(Epidermal growth factor), A1AT(Alpha-1-antitrypsin), tPAI-1(Total plasminogen activator inhibitor-1), ApoA-1(Apolipoprotein-A1), proApoA-1(Proapolipoprotein-A1), Kininogen, VDBP(Vitamin D-binding protein), ApoA-1/proApoA-1, CRP/Kininogen, Hemoglobin, Cathepsin B(CB), MPO(myeloperoxidase) and IL-1ra(Interleukin-1 receptor antagonist)

Protein markers for monitoring, diagnosis and screening of breast cancer and the method of monitoring, diagnosis and screening using thereof

The present invention relates to a protein marker for breast-cancer monitoring, diagnosis and screening, and a breast-cancer monitoring, diagnosis and screening method using the same. More specifically, it relates to a method for the monitoring, diagnosis and screening of breast-cancer through the use of a protein marker whose expression is either increased or decreased specifically for breast-cancer patients. The method for the monitoring, diagnosis and screening of breast-cancer using a protein marker according to the present invention can make a contribution to improving survival rates in breast-cancer patients and reducing national losses due to cancer treatment by making rapid treatment possible. This is achieved by enabling diagnosis and screening, and assessment of the extent of progression of breast-cancer, at an early stage in the breast cancer, by finding differences in the levels of marker protein expression in healthy individuals and breast-cancer patients.

Protein marker for breast-cancer monitoring, diagnosis and screening, and a breast-cancer monitoring, diagnosis and screening method using the same

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