The van der Waals (vdW) materials with low dimensions have been extensively studied as a platform to generate exotic quantum properties [1][2][3][4][5][6]. Advancing this view, a great deal of attention is currently paid to topological quantum materials with vdW structures, which give new concepts in designing the functionality of materials. Here, we present the first experimental realization of a higher-order topological insulator by investigating a quasi-one-dimensional (quasi-1D) bismuth bromide Bi 4 Br 4 [7][8][9][10][11] built from a vdW stacking of quantum spin Hall insulators (QSHI) [12] with angle-resolved photoemission spectroscopy (ARPES). The quasi-1D bismuth halides can select various topological phases by different stacking procedures of vdW chains, offering a fascinating playground for engineering topologically non-trivial edge-states toward future spintronics applications.The Z 2 weak topological insulator (WTI) phases have been confirmed in the materials with stacked QSHI layers, where the side-surface becomes topologically non-trivial by accumulating helical edge states of QSHI layers [13,14]. Similarly, higher-order topological insulators (HOTIs) are expected to be built from stacking QSHIs, which, however, accumulate the 1D edge-states to develop 1D helical hinge-states in a 3D crystal [15,16]. Such HOTI phases have been theoretically predicted recently in materials previously regarded as trivial insulators under the Z 2 criterion by extending the topological classification to the Z 4 topological index [17][18][19][20][21][22]. To date, only one material has been experimentally confirmed to be in the higher-order topological phase, which is bulk bismuth [23]. However, bulk bismuth is a semimetal, which cannot become insulating even by carrier doping. Materials science is, therefore, awaiting the first experimental realization of a HOTI, which enables one to explore various quantum phenomena including spin currents around hinges and quantized conductance under the external fields.A quasi-1D bismuth bromide, Bi 4 Br 4 , with a bilayer structure of chains (Fig. 1b) is theoretically predicted to be a topological crystalline insulator of Z 2,2,2,4 = {0, 0, 0, 2}, protected by the C 2 -rotation symmetry [10,11,[19][20][21]. This state should develop 2D topological surface states in the cross-section (010) of the chains [24,25]. Significantly, theory also categorizes this system as a HOTI, and expects that 1D helical hinge-states emerge between the top-surface (001) and the side-surface (100) of a crystal due to the second-order bulk-boundary correspondence [10,11]. Nevertheless, the topological phase of Bi 4 Br 4 has

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the most sensitive method for the detection of nucleic acids. 14 In hepatitis A virus (HAV) infection, fecal excretion ofA recent report on an outbreak of hepatitis A in a neonatal the virus has been reported to cease shortly after sympintensive care unit reported the occurrence of prolonged extoms occur. Although there have been several reports cretion of HAV RNA in stool (as long as 6 months) much on detection of HAV in feces using polymerase chain longer than previously reported. 15 However, neonates may reaction (PCR), the duration of fecal HAV shedding in excrete HAV in stool for longer than adults because of their human adult hepatitis A has not been well described. In underdeveloped immunity.15 the present study, we applied the reverse-transcription In the present study, we determined HAV RNA in stools (RT)-PCR system to the detection of fecal HAV RNA in from adult patients using the two-stage reverse-transcription 10 patients with sporadic hepatitis A. The viral genomic (RT)-PCR method 16 and found that fecal shedding of HAV RNA was detected in the stools from five patients after continued for up to 3 months after onset of illness, and even the onset of clinical symptoms. All stool samples colafter the normalization of the serum ALT levels. ied by several methods. Immunoelectron microscopy has dis-sera as described previously.16 RNA pellets from 100 mL of sera were closed that HAV antigen is detectable in the stool before the dissolved in 25 mL of distilled water and subjected to PCR. Stool development of jaundice and peaking of serum alanine trans-RNA was extracted by the same method from 400 mL of 10% stool suspension in phosphate-buffered saline (pH 7.4).aminase (ALT) levels. Taq under the same conditions as used for the first amplification.Address reprint requests to: Kazuhiko Koike, M.D., First Department of Internal MediAliquots of the resulting samples were electrophoresed in 6% polycine,

In cuprate superconductors with high critical transition temperature (Tc), light hole-doping to the parent compound, which is an antiferromagnetic Mott insulator, has been predicted to lead to the formation of small Fermi pockets. These pockets, however, have not been observed. Here, we investigate the electronic structure of the five-layered Ba2Ca4Cu5O10(F,O)2, which has inner copper oxide (CuO2) planes with extremely low disorder, and find small Fermi pockets centered at (π/2, π/2) of the Brillouin zone by angle-resolved photoemission spectroscopy and quantum oscillation measurements. The d-wave superconducting gap opens along the pocket, revealing the coexistence between superconductivity and antiferromagnetic ordering in the same CuO2 sheet. These data further indicate that superconductivity can occur without contribution from the antinodal region around (π, 0), which is shared by other competing excitations.

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