Erratum: Large Unidirectional Magnetoresistance in a Magnetic Topological Insulator [Phys. Rev. Lett. 117, 127202 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.117.127202.

Current-driven magnetization switching in ferromagnetic bulk Rashba semiconductor (Ge,Mn)Te.

Multiferroic materials with both ferroelectric and ferromagnetic orders provide a promising arena for the electrical manipulation of magnetization through the mutual correlation between those ferroic orders. Such a concept of multiferroics may expand to semiconductor with both broken symmetries of spatial inversion and time reversal, that is, polar ferromagnetic semiconductors. Here, we report the observation of current-driven magnetization switching in one such example, (Ge,Mn)Te thin films. The ferromagnetism caused by Mn doping opens an exchange gap in original massless Dirac band of the polar semiconductor GeTe with Rashba-type spin-split bands. The anomalous Hall conductivity is enhanced with increasing hole carrier density, indicating that the contribution of the Berry phase is maximized as the Fermi level approaches the exchange gap. By means of pulse-current injection, the electrical switching of the magnetization is observed in the (Ge,Mn)Te thin films as thick as 200 nm, pointing to the Rashba-Edelstein effect of bulk origin. The efficiency of this effect strongly depends on the Fermi-level position owing to the efficient spin accumulation at around the gap. The magnetic bulk Rashba system will be a promising platform for exploring the functional correlations among electric polarization, magnetization, and current.

Quantized chiral edge conduction on domain walls of a magnetic topological insulator.

Electronic ordering in magnetic and dielectric materials forms domains with different signs of order parameters. The control of configuration and motion of the domain walls (DWs) enables nonvolatile responses against minute external fields. Here, we realize chiral edge states (CESs) on the magnetic DWs of a magnetic topological insulator. We design and fabricate the magnetic domains in the quantum anomalous Hall state with the tip of a magnetic force microscope and prove the existence of the chiral one-dimensional edge conduction along the prescribed DWs through transport measurements. The proof-of-concept devices based on reconfigurable CESs and Landauer-Büttiker formalism are realized for multiple-domain configurations with well-defined DW channels. Our results may lead to the realization of low-power-consumption spintronic devices.

A magnetic heterostructure of topological insulators as a candidate for an axion insulator.

The axion insulator which may exhibit an exotic quantized magnetoelectric effect is one of the most interesting quantum phases predicted for the three-dimensional topological insulator (TI). The axion insulator state is expected to show up in magnetically doped TIs with magnetizations pointing inwards and outwards from the respective surfaces. Towards the realization of the axion insulator, we here engineered a TI heterostructure in which magnetic ions (Cr) are modulation-doped only in the vicinity of the top and bottom surfaces of the TI ((Bi,Sb)2Te3) film. A separation layer between the two magnetic layers weakens interlayer coupling between them, enabling the magnetization reversal of individual layers. We demonstrate the realization of the axion insulator by observing a zero Hall plateau (ZHP) (where both the Hall and longitudinal conductivity become zero) in the electric transport properties, excluding the other possible origins for the ZHP. The manifestation of the axion insulator can lead to a new stage of research on novel magnetoelectric responses in topological matter.

Current-Nonlinear Hall Effect and Spin-Orbit Torque Magnetization Switching in a Magnetic Topological Insulator.

The current-nonlinear Hall effect or second harmonic Hall voltage is widely used as one of the methods for estimating charge-spin conversion efficiency, which is attributed to the magnetization oscillation by spin-orbit torque (SOT). Here, we argue the second harmonic Hall voltage under a large in-plane magnetic field with an in-plane magnetization configuration in magnetic-nonmagnetic topological insulator (TI) heterostructures, Cr_{x}(Bi_{1-y}Sb_{y})_{2-x}Te_{3}/(Bi_{1-y}Sb_{y})_{2}Te_{3}, where it is clearly shown that the large second harmonic voltage is governed not by SOT but mainly by asymmetric magnon scattering without macroscopic magnetization oscillation. Thus, this method does not allow an accurate estimation of charge-spin conversion efficiency in TI. Instead, the SOT contribution is exemplified by current pulse induced nonvolatile magnetization switching, which is realized with a current density of 2.5×10^{10} A m^{-2}, showing its potential as a spintronic material.

Large Unidirectional Magnetoresistance in a Magnetic Topological Insulator.

We report current-direction dependent or unidirectional magnetoresistance (UMR) in magnetic or nonmagnetic topological insulator (TI) heterostructures, Cr_{x}(Bi_{1-y}Sb_{y})_{2-x}Te_{3}/(Bi_{1-y}Sb_{y})_{2}Te_{3}, that is several orders of magnitude larger than in other reported systems. From the magnetic field and temperature dependence, the UMR is identified to originate from the asymmetric scattering of electrons by magnons. In particular, the large magnitude of UMR is an outcome of spin-momentum locking and a small Fermi wave number at the surface of TI. In fact, the UMR is maximized around the Dirac point with the minimal Fermi wave number.

Zero-bias photocurrent in ferromagnetic topological insulator.

Magnetic interactions in topological insulators cause essential modifications in the originally mass-less surface states. They offer a mass gap at the Dirac point and/or largely deform the energy dispersion, providing a new path towards exotic physics and applications to realize dissipation-less electronics. The nonequilibrium electron dynamics at these modified Dirac states unveil additional functions, such as highly efficient photon to spin-current conversion. Here we demonstrate the generation of large zero-bias photocurrent in magnetic topological insulator thin films on mid-infrared photoexcitation, pointing to the controllable band asymmetry in the momentum space. The photocurrent spectra with a maximal response to the intra-Dirac-band excitations can be a sensitive measure for the correlation between Dirac electrons and magnetic moments.

Quantum Hall states stabilized in semi-magnetic bilayers of topological insulators.

By breaking the time-reversal symmetry in three-dimensional topological insulators with the introduction of spontaneous magnetization or application of magnetic field, the surface states become gapped, leading to quantum anomalous Hall effect or quantum Hall effect, when the chemical potential locates inside the gap. Further breaking of inversion symmetry is possible by employing magnetic topological insulator heterostructures that host non-degenerate top and bottom surface states. Here we demonstrate the tailored-material approach for the realization of robust quantum Hall states in the bilayer system, in which the cooperative or cancelling combination of the anomalous and ordinary Hall responses from the respective magnetic and non-magnetic layers is exemplified. The appearance of quantum Hall states at filling factor 0 and +1 can be understood by the relationship of energy band diagrams for the two independent surface states. The designable heterostructures of magnetic topological insulator may explore a new arena for intriguing topological transport and functionality.

Quantum Hall effect on top and bottom surface states of topological insulator (Bi1-xSbx)2Te3 films.

The three-dimensional topological insulator is a novel state of matter characterized by two-dimensional metallic Dirac states on its surface. To verify the topological nature of the surface states, Bi-based chalcogenides such as Bi2Se3, Bi2Te3, Sb2Te3 and their combined/mixed compounds have been intensively studied. Here, we report the realization of the quantum Hall effect on the surface Dirac states in (Bi1-xSbx)2Te3 films. With electrostatic gate-tuning of the Fermi level in the bulk band gap under magnetic fields, the quantum Hall states with filling factor ±1 are resolved. Furthermore, the appearance of a quantum Hall plateau at filling factor zero reflects a pseudo-spin Hall insulator state when the Fermi level is tuned in between the energy levels of the non-degenerate top and bottom surface Dirac points. The observation of the quantum Hall effect in three-dimensional topological insulator films may pave a way toward topological insulator-based electronics.

Dirac electron states formed at the heterointerface between a topological insulator and a conventional semiconductor.

Topological insulators are a class of semiconductor exhibiting charge-gapped insulating behaviour in the bulk, but hosting a spin-polarized massless Dirac electron state at the surface. The presence of a topologically protected helical edge channel has been verified for the vacuum-facing surface of several topological insulators by means of angle-resolved photoemission spectroscopy and scanning tunnelling microscopy. By performing tunnelling spectroscopy on heterojunction devices composed of p-type topological insulator (Bi1−xSbx)2Te3 and n-type conventional semiconductor InP, we report the observation of such states at the solid-state interface. Under an applied magnetic field, we observe a resonance in the tunnelling conductance through the heterojunction due to the formation of Landau levels of two-dimensional Dirac electrons at the interface. Moreover, resonant tunnelling spectroscopy reveals a systematic dependence of the Fermi velocity and Dirac point energy on the composition x. The successful formation of robust non-trivial edge channels at a solid-state interface is an essential step towards functional junctions based on topological insulators.

[Immunohistological study of the nasal mucosa with reference to gamma delta-T cells].

The distribution of gamma delta-T cells (gamma delta-TCR positive cells) in nasal mucosa and polyps was studied in patients with nasal allergy and non-allergic patients. The biopsy specimens from the inferior turbinate and resected polyps were frozen at -70 degrees C and sliced at a thickness of 4 microns with a cryostat. Monoclonal antibodies (CD3 and TCR-gamma delta-1) and the Labelled Streptavidin Biotin method were used to detect T lymphocytes and gamma delta-T cells. The results were as follows: 1) The rate of gamma delta-T cells in the epithelium is higher than that in the lamina propria in patients with nasal allergy. 2) In non-allergic patients, on the other hand, the rate of gamma delta-T cells was almost the same in these layers. 3) The distribution of gamma delta-T cells in nasal polyps was uniform and their rate was relatively high. It has been reported that gamma delta-T cells can recognize a stress antigen such as heat shock protein. These cells are thought to play an important role in non-specific immunoreactions. This study suggests that gamma delta-T cells in the nasal mucosa play an important role also in specific immunoreactions.

[Histological and immunohistochemical study of nasal polyps].

Nasal polyps, in general, have been histologically classified as edematous, adenocystic and fibrous types. It has recently been pointed out that eosinophilic infiltration in nasal polyps has increased along with an increase in nasal allergy. The purpose of this study was to classify the nasal polyps histologically and to examine the mode of infiltration and activation of eosinophils by means of immunohistochemistry. The subjects were 101 patients who underwent surgery for nasal polyps. There were 66 males and 35 females ranging in age from 12 to 76 years. Resected polyps were fixed in formalin, embedded in paraffin, and sliced at a thickness of 4 microns. Hematoxylin-eosin staining and streptavidin- biotinyl peroxidase complex staining were used to detect eosinophils. The results were as follows: 1) The nasal polyps were, histologically, edematous in 88.1%, adenocystic in 47.5%, and fibrous in 19.8%. 2) The number and distribution of EG1-positive cells and EG2-positive cells were almost the same in the superficial layer of the lamina propria. This study suggests that eosinophilic infiltration into nasal polyps occurs mainly in edematous polyps and that the majority of the infiltrating eosinophils are activated.

[Immunohistological study of the nasal mucosa in latent allergic patients].

We studied the distribution of T lymphocyte subpopulations and EG2 positive cells in the inferior turbinates of subjects with latent nasal allergy by use of an immunohistochemical procedure. Five patients who had a positive skin test for house dust and one who had a positive skin test for Japanese cedar were studied. The specimens were frozen at -70 degrees C and sliced at 4 microns with a cryostat. The peroxidaseantiperoxidase method with monoclonal antibodies (CD4, CD8, EG2) was used to detect T lymphocyte subpopulations and activated eosinophils. Finally, the specimens were counterstained with Mayer's Hematoxylin. CD4 positive cells and CD8 positive cells were found mainly in the superficial layer of the lamina propria. In every subject, the number of CD4 positive cells dominated that of CD8 positive cells in the lamina propria. The ratio of CD4 positive cells to CD8 positive cells was 1.93, on average. This ratio was lower than the ratio typical of nasal allergy, but higher than the ratio of non-allergic normal controls. Though the number of EG2 positive cells was lower than the number typical of nasal allergy, EG2 positive cells were observed in every case. We speculate that latent nasal allergic reactions may develop in the inferior turbinates.

[Immunohistological study of eosinophilic infiltration of nasal polyps in aspirin-induced asthma].

It is well known that nasal polyps frequently develop in patients with aspirin-induced asthma, which is thought to be a non-atopic disease. We immunohistochemically examined the eosinophils infiltrating the nasal polyps in patients with aspirin-induced asthma. It has also been established that the monoclonal antibody EG1 reacts with both stored and secretion type ECP (eosinophil cationic protein), and that EG2 reacts only with the secretion type of ECP. EG2 positive cells may thus be considered to be activated eosinophils. Seven cases with nasal polyps associated with aspirin-induced asthma participated in our study. Blood eosinophilia was observed in all 7 cases, but 6 showed normal blood values IgE. Two reacted to house dust antigen, on skin tests and RAST. In the nasal polyps, many EG2 positive cells were observed. On serial sections, the number and distribution of EG1 and EG2 positive cells were almost equal. In the superficial lamina propria, extra-cellular release of ECP was noted. However, epithelial damage did not relate to the number of EG2 positive cells or the degree of extra-cellular EG2 release. In the deep lamina propria, slight extra-cellular ECP release was found. From these results, the eosinophils in nasal polyps accompanying aspirin-induced asthma were thought to be activated. Eosinophils seem to play an important role in the development of nasal polyps. However, tissue injury induced by eosinophils, was not be demonstrated in this study.

[Immunohistologic study of the nasal mucosa with reference to Langerhans cells].

The distribution of Langerhans cells in human oral mucosa, nasal mucosa and nasal polyps was studied by means of immunohistochemistry. Our study involved 35 participants. The specimens were frozen to -70 degrees C and sliced at 4 microns with a cryostat. Monoclonal antibodies CD1 (OKT6) and the peroxidase-antiperoxidase staining method were used to detect Langerhans cells. In the oral mucosa and the nasal vestibule lined with stratified squamous epithelium, CD1 positive cells were observed and these cells were dendric in form. The cells were found mainly from the intermediate layer to the deep layer of the epithelium. In the inferior turbinate lined with ciliated epithelium, we could not find any CD1 positive cells at all. The nasal polyps in some cases had a normal ciliated columnar epithelium while others had metaplastic stratified squamous epithelium. Both types of epithelium in the same polyp were noted on some occasions. In nasal polyps, CD1 positive cells which showed dendric form were found in the metaplastic squamous epithelium only, and could not be observed in the ciliated columnar epithelium at all. Based on the above results, the presence of Langerhans cells is confirmed not by the anatomical location but by the type of epithelium. Langerhans cells could be detected only in the squamous epithelium. Keratinocytes, which constitute the squamous epithelium, are known to release cytokines. IL-1 (interleukin-1) and GM-CSF (granulocyte-macrophage colony stimulating factor) released from keratinocytes are thought to influence the viability and function of Langerhans cells. The migration of Langerhans cells into squamous epithelium may be regulated by cytokines released from keratinocytes.

Geographical distribution of isozyme alleles for phosphogluconate dehydrogenase in barley.

The Ak and Tj alleles at the Pgd1 locus and the Ps and Tn alleles at the Pgd2 locus were detected for phosphogluconate dehydrogenase in barley. The Ak allele at the Pgd1 locus was widely distributed around the world, while the Tj allele was found only in two accessions from Nepal and one from India. At the Pgd2 locus, the Ps allele was abundant everywhere, whereas the Tn allele was occasionally found in Caucasus, Turkey, and Europe, and scarcely or none in Korea, China, Nepal, India, and Ethiopia. The Tn allele was also detected in Japanese accessions. Among them, six-rowed varieties carrying the Tn allele were principally grown in northern parts of Japan and characterized by covered kernel, the Occidental type for nonbrittleness of rachis, and resistance to Japanese races of powdery mildew. However, the loci responsible for these characteristics were independent of the Pgd1 locus.

[The role of eosinophil in nasal allergy].

In this paper, the function of the eosinophil, activation of the eosinophil and degranulation of eosinophil granules are discussed. The in vitro mechanism of eosinophil-induced tissue injury has been reported previously. We have reported that most of the eosinophils in the inferior turbinate mucous membrane of nasal allergy were positive to EG2 and have also reported that extracellular deposits of EG2, MBP and EPO were mainly found in the superficial lamina propria. However, damage of the epithelia did not relate to the infiltration of EG2, MBP and EPO. The damage of the basement membrane could not be found. The concept of tissue injury induced by eosinophil, is controversial, and further study is required to elucidate the function of the eosinophil, in vivo.

[Immunohistological study of the nasal mucosa in allergic rhinitis with reference to B cell, T cell subpopulation, activated T cell and Langerhans cell].

Distribution of B lymphocytes, T lymphocytes subpopulations, activated T lymphocytes and Langerhans cells of the nasal mucosa in 28 patients with nasal allergy ranging in age from 19 years to 54 years was studied. The specimens from inferior turbinates were frozen at -70 degrees C and sliced at a thickness of 4 microns by cryostat. Monoclonal antibodies and peroxidase-antiperoxidase staining (Ortho) were used to detect these cells. OKT4, OKT8, OKT6 and OKB19 were used as markers of helper/inducer T cells, suppresser/cytotoxic T cells, Langerhans cells and B cells, respectively. OKDR was used as a marker of activated T cells, B cells, Langerhans cells and macrophages. Many OKT4 and OKT8 positive cells were observed in lamina propria. In every case, more OKT4 positive cells were detected in number than OKT8 positive cells. Some OKB19 positive cells and macrophages were observed in lamina propria, but OKT6 positive cells were not observed. OKDR positive cells were observed in high density, and more OKDR positive cells were detected than OKT4, OKT8 and OKB19 positive cells. Most of the OKDR positive cells were small in size and round in shape. From these results, many T lymphocytes were thought to be activated, and T lymphocytes were thought to play an important role in nasal allergy.

[Detection of immunoglobulin in the inner ear tissue by PAP method].

The distribution of immunoglobulins IgG, IgA and IgM in the inner ear tissue from a patient who died of lung bleeding followed after sepsis was studied, and also the normal guinea pig inner ears and the inner ear disorders induced by Kanamycin injection were studied for the distribution of IgG. The temporal bones were fixed in formaldehyde, decalcified in EDTA and embedded in paraffin. The PAP method was used for the demonstration of the immunoglobulins. In both the human inner ear tissue and the normal control inner ear tissue of the guinea pigs deposits of IgG were found in the sensory organs and the endolymphatic sac, however, in the stria vascularis was slight. The severe damaged inner ears induced by Kanamycin the remarkable decreased deposits of IgG were found in the cochlea, but in the endolymphatic sac the remarkable increased deposits of IgG were found. No IgA and IgM were found in the human inner ear tissue.