Time-reversal symmetry-breaking charge order in a kagome superconductor.

The kagome lattice1, which is the most prominent structural motif in quantum physics, benefits from inherent non-trivial geometry so that it can host diverse quantum phases, ranging from spin-liquid phases, to topological matter, to intertwined orders2-8 and, most rarely, to unconventional superconductivity6,9. Recently, charge sensitive probes have indicated that the kagome superconductors AV3Sb5 (A = K, Rb, Cs)9-11 exhibit unconventional chiral charge order12-19, which is analogous to the long-sought-after quantum order in the Haldane model20 or Varma model21. However, direct evidence for the time-reversal symmetry breaking of the charge order remains elusive. Here we use muon spin relaxation to probe the kagome charge order and superconductivity in KV3Sb5. We observe a noticeable enhancement of the internal field width sensed by the muon ensemble, which takes place just below the charge ordering temperature and persists into the superconducting state. Notably, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. We further show the multigap nature of superconductivity in KV3Sb5 and that the [Formula: see text] ratio (where Tc is the superconducting transition temperature and λab is the magnetic penetration depth in the kagome plane) is comparable to those of unconventional high-temperature superconductors. Our results point to time-reversal symmetry-breaking charge order intertwining with unconventional superconductivity in the correlated kagome lattice.

Photocurrent-driven transient symmetry breaking in the Weyl semimetal TaAs.

Symmetry plays a central role in conventional and topological phases of matter, making the ability to optically drive symmetry changes a critical step in developing future technologies that rely on such control. Topological materials, like topological semimetals, are particularly sensitive to a breaking or restoring of time-reversal and crystalline symmetries, which affect both bulk and surface electronic states. While previous studies have focused on controlling symmetry via coupling to the crystal lattice, we demonstrate here an all-electronic mechanism based on photocurrent generation. Using second harmonic generation spectroscopy as a sensitive probe of symmetry changes, we observe an ultrafast breaking of time-reversal and spatial symmetries following femtosecond optical excitation in the prototypical type-I Weyl semimetal TaAs. Our results show that optically driven photocurrents can be tailored to explicitly break electronic symmetry in a generic fashion, opening up the possibility of driving phase transitions between symmetry-protected states on ultrafast timescales.

Non-Kondo-like electronic structure in the correlated rare-earth hexaboride YbB(6).

We present angle-resolved photoemission studies on the rare-earth-hexaboride YbB(6), which has recently been predicted to be a topological Kondo insulator. Our data do not agree with the prediction and instead show that YbB(6) exhibits a novel topological insulator state in the absence of a Kondo mechanism. We find that the Fermi level electronic structure of YbB(6) has three 2D Dirac cone like surface states enclosing the Kramers's points, while the f orbital that would be relevant for the Kondo mechanism is ∼1 eV below the Fermi level. Our first-principles calculation shows that the topological state that we observe in YbB(6) is due to an inversion between Yb d and B p bands. These experimental and theoretical results provide a new approach for realizing novel correlated topological insulator states in rare-earth materials.

Topological surface states protected from backscattering by chiral spin texture.

Topological insulators are a new class of insulators in which a bulk gap for electronic excitations is generated because of the strong spin-orbit coupling inherent to these systems. These materials are distinguished from ordinary insulators by the presence of gapless metallic surface states, resembling chiral edge modes in quantum Hall systems, but with unconventional spin textures. A key predicted feature of such spin-textured boundary states is their insensitivity to spin-independent scattering, which is thought to protect them from backscattering and localization. Recently, experimental and theoretical efforts have provided strong evidence for the existence of both two- and three-dimensional classes of such topological insulator materials in semiconductor quantum well structures and several bismuth-based compounds, but so far experiments have not probed the sensitivity of these chiral states to scattering. Here we use scanning tunnelling spectroscopy and angle-resolved photoemission spectroscopy to visualize the gapless surface states in the three-dimensional topological insulator Bi(1-x)Sb(x), and examine in detail the influence of scattering from disorder caused by random alloying in this compound. We show that, despite strong atomic scale disorder, backscattering between states of opposite momentum and opposite spin is absent. Our observations demonstrate that the chiral nature of these states protects the spin of the carriers. These chiral states are therefore potentially useful for spin-based electronics, in which long spin coherence is critical, and also for quantum computing applications, where topological protection can enable fault-tolerant information processing.

A tunable topological insulator in the spin helical Dirac transport regime.

Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose-Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators-materials with a bulk insulating gap of spin-orbit origin and surface states protected against scattering by time-reversal symmetry-and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuth-based class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a non-trivial Berry's phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spin-texture in stoichiometric Bi(2)Se(3).M(x) (M(x) indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spin-polarized edge channels in spintronic and computing technologies possibly at room temperature.

A topological Dirac insulator in a quantum spin Hall phase.

When electrons are subject to a large external magnetic field, the conventional charge quantum Hall effect dictates that an electronic excitation gap is generated in the sample bulk, but metallic conduction is permitted at the boundary. Recent theoretical models suggest that certain bulk insulators with large spin-orbit interactions may also naturally support conducting topological boundary states in the quantum limit, which opens up the possibility for studying unusual quantum Hall-like phenomena in zero external magnetic fields. Bulk Bi(1-x)Sb(x) single crystals are predicted to be prime candidates for one such unusual Hall phase of matter known as the topological insulator. The hallmark of a topological insulator is the existence of metallic surface states that are higher-dimensional analogues of the edge states that characterize a quantum spin Hall insulator. In addition to its interesting boundary states, the bulk of Bi(1-x)Sb(x) is predicted to exhibit three-dimensional Dirac particles, another topic of heightened current interest following the new findings in two-dimensional graphene and charge quantum Hall fractionalization observed in pure bismuth. However, despite numerous transport and magnetic measurements on the Bi(1-x)Sb(x) family since the 1960s, no direct evidence of either topological Hall states or bulk Dirac particles has been found. Here, using incident-photon-energy-modulated angle-resolved photoemission spectroscopy (IPEM-ARPES), we report the direct observation of massive Dirac particles in the bulk of Bi(0.9)Sb(0.1), locate the Kramers points at the sample's boundary and provide a comprehensive mapping of the Dirac insulator's gapless surface electron bands. These findings taken together suggest that the observed surface state on the boundary of the bulk insulator is a realization of the 'topological metal'. They also suggest that this material has potential application in developing next-generation quantum computing devices that may incorporate 'light-like' bulk carriers and spin-textured surface currents.

Comparative Study of Treatment Outcome with Tenofovir Alafenamide and Entecavir in Patients with HBV Related Acute on Chronic Liver Failure.

Major causes of acute insult in Hepatitis B virus related acute on chronic liver failure in the Asian region are reactivation of Hepatitis B virus and super infection with hepatitis A and E virus (ACLF). Anti viral therapy should be started as soon as possible in the ACLF patients at presentation while waiting for confirmation by HBV DNA level. This randomized controlled trial was carried out at the Department of Hepatology, BSMMU, Bangladesh from September 2019 to august 2020 with Hepatitis B virus related ACLF patient. This trial was conducted among twenty seven HBV acute on chronic liver failure patient to compare Child Turcotte pugh (CTP) score, Model for end stage liver disease (MELD) score, Asia Pacific Association for study of Liver (APASL) ACLF Research consortium (AARC) score, survival of the patients and HBV DNA level at 3 months with antiviral therapy between tenofovir alafenamide (25mg) and entecavir (0.5mg) group. CTP score, MELD score and AARC score were significantly (p<0.05) decline from baseline to all subsequent follow-up at 1st (at 7 days), 2nd (at 14 days), 3rd (at 30 days) and 4th (at 90 days) in each group but non significant (p>0.05) difference occurred between two group. All twenty seven patients had detectable HBV DNA level at pre-treatment and all survived patients became undectable at 4th, 90 days follow-up. Total 10 patients (37.07%) were survived at 90 days follow-up, out of them seven patients (70.0%) were in tenofovir alafenamide group and three patients (30.0%) were in entecavir group which was statistically significant (p<0.05) in between two group. Hepatic encephalopathy and hepatorenal syndrome were most common causes of death in both groups. Both drugs tenofovir alafenamide and entecavir significantly improves liver functions but the former one is superior regarding survival.

Changes in Serum Uric Acid Level in Acute Myocardial Infarction Patients.

Myocardial infarction (MI) is one of the dangerous manifestations of coronary artery disease and one of the commonest causes of mortality. This cross-sectional study was carried out in the department of Biochemistry, Mymensingh Medical College in collaboration with the department of Cardiology, Mymensingh Medical College Hospital, Mymensingh, Bangladesh during the period of January 2018 to December 2018. A total of 120 subjects were included in this study. Among them 60 were diagnosed AMI patients denoted as case group and 60 were apparently normal healthy individuals denoted as control group. Biochemical values were expressed as Mean±SD (Standard deviation). Statistical analysis was done by using SPSS (Statistical package for social science) version 21.0 windows package. Serum uric acid determined by enzymatic colorimetric method using the test kit. Among the study groups the mean±SD values of uric acid were 6.61±2.62 and 5.38±1.16mg/dl in case and control group respectively. The analysis showed that, serum uric acid was statistically increased in case group compared with control group. The level of significance was 0.001. Statistical significance of difference between two groups were evaluated by using Student's unpaired 't' test.

Serum Magnesium Level and It's Relation in Predicting Adverse In-Hospital Outcome in Patients with First Attack of Myocardial Infarction.

Acute myocardial infarction (AMI) patients characterize a large proportion of admissions in coronary care unit and their management and risk stratification is of immense importance. Hypomagnesemia is a long-term risk factor for incident of both myocardial infarction and arrhythmia. We assessed whether serum magnesium levels at admission is associated with arrhythmias and in-hospital mortality in patients with acute myocardial infarction (AMI). The aim of the study was to evaluate the prognostic implications of serum magnesium level in patients with acute myocardial infarction. This cross-sectional observational study was conducted in the department of cardiology in Mymensingh Medical College Hospital from October 2017 to March 2019. Total 259 acute myocardial infarction patients were included considering inclusion and exclusion criteria. The sample population was divided into two groups: Group-I: Patients with acute myocardial infarction with serum magnesium ≥1.82mg/dl. Group-II: Patients with acute myocardial infarction with serum magnesium <1.82mg/dl. Serum magnesium level was measured on admission, and the incidence of in-hospital major cardiac events was assessed. In this study mean serum magnesium level of Group-I, Group-II were 2.21±0.14mg/dl, 1.60±0.15mg/dl respectively. It was statistically significant (p<0.05). In-hospital outcomes of the study group revealed that low risk group patients were uneventful outcome during hospitalization period, they had no any complication. In Group-I patient, 9(4.8%) were developed arrhythmias, 26(13.9%) were developed heart failure, 9(4.8%) were developed cardiogenic shock and 3(1.6%) were died and in Group-II patient, 44(61.10%) developed arrhythmias, 9(12.50%) were developed heart failure, 7(9.7%) were developed cardiogenic shock and 12(16.7%) were died out of them which was statistically significant (p<0.05). Mean duration of hospital stay of the study population according serum magnesium level was in Group-I, 4.27±0.68 days, in Group-II, 5.84±1.05 days which was statistically significant (p<0.05). In conclusion patient with serum magnesium level less than 1.82mg/dl increased the risk of in-hospital arrhythmia and death.

Tunable unconventional kagome superconductivity in charge ordered RbV3Sb5 and KV3Sb5.

Unconventional superconductors often feature competing orders, small superfluid density, and nodal electronic pairing. While unusual superconductivity has been proposed in the kagome metals AV3Sb5, key spectroscopic evidence has remained elusive. Here we utilize pressure-tuned and ultra-low temperature muon spin spectroscopy to uncover the unconventional nature of superconductivity in RbV3Sb5 and KV3Sb5. At ambient pressure, we observed time-reversal symmetry breaking charge order below [Formula: see text] 110 K in RbV3Sb5 with an additional transition at [Formula: see text] 50 K. Remarkably, the superconducting state displays a nodal energy gap and a reduced superfluid density, which can be attributed to the competition with the charge order. Upon applying pressure, the charge-order transitions are suppressed, the superfluid density increases, and the superconducting state progressively evolves from nodal to nodeless. Once optimal superconductivity is achieved, we find a superconducting pairing state that is not only fully gapped, but also spontaneously breaks time-reversal symmetry. Our results point to unprecedented tunable nodal kagome superconductivity competing with time-reversal symmetry-breaking charge order and offer unique insights into the nature of the pairing state.

Hidden magnetism uncovered in a charge ordered bilayer kagome material ScV6Sn6.

Charge ordered kagome lattices have been demonstrated to be intriguing platforms for studying the intertwining of topology, correlation, and magnetism. The recently discovered charge ordered kagome material ScV6Sn6 does not feature a magnetic groundstate or excitations, thus it is often regarded as a conventional paramagnet. Here, using advanced muon-spin rotation spectroscopy, we uncover an unexpected hidden magnetism of the charge order. We observe an enhancement of the internal field width sensed by the muon ensemble, which takes place within the charge ordered state. More importantly, the muon spin relaxation rate below the charge ordering temperature is substantially enhanced by applying an external magnetic field. Taken together with the hidden magnetism found in AV3Sb5 (A = K, Rb, Cs) and FeGe kagome systems, our results suggest ubiqitous time-reversal symmetry-breaking in charge ordered kagome lattices.

Discovery of conjoined charge density waves in the kagome superconductor CsV3Sb5.

The electronic instabilities in CsV3Sb5 are believed to originate from the V 3d-electrons on the kagome plane, however the role of Sb 5p-electrons for 3-dimensional orders is largely unexplored. Here, using resonant tender X-ray scattering and high-pressure X-ray scattering, we report a rare realization of conjoined charge density waves (CDWs) in CsV3Sb5, where a 2 × 2 × 1 CDW in the kagome sublattice and a Sb 5p-electron assisted 2 × 2 × 2 CDW coexist. At ambient pressure, we discover a resonant enhancement on Sb L1-edge (2s→5p) at the 2 × 2 × 2 CDW wavevectors. The resonance, however, is absent at the 2 × 2 × 1 CDW wavevectors. Applying hydrostatic pressure, CDW transition temperatures are separated, where the 2 × 2 × 2 CDW emerges 4 K above the 2 × 2 × 1 CDW at 1 GPa. These observations demonstrate that symmetry-breaking phases in CsV3Sb5 go beyond the minimal framework of kagome electronic bands near van Hove filling.

Single-Dirac-cone topological surface states in the TlBiSe(2) class of topological semiconductors.

We investigate several strong spin-orbit coupling ternary chalcogenides related to the (Pb,Sn)Te series of compounds. Our first-principles calculations predict the low-temperature rhombohedral ordered phase in TlBiTe2, TlBiSe2, and TlSbX2 (X=Te, Se, S) to be topologically nontrivial. We identify the specific surface termination that realizes the single Dirac cone through first-principles surface state computations. This termination minimizes effects of dangling bonds, making it favorable for photoemission experiments. In addition, our analysis predicts that thin films of these materials could harbor novel 2D quantum spin Hall states, and support odd-parity topological superconductivity.

Relationship of Plasma Vitamin-D Level with Left Ventricular Ejection Fraction in Patients with First Attack of Acute Myocardial Infarction.

It has been widely reported that vitamin D deficiency is associated with Coronary heart disease (CHD), especially acute Myocardial infarction (MI). Many factors are responsible for reduced Left ventricular ejection fraction (LVEF) and acute Left ventricular fraction (LVF) after acute MI. This cross sectional descriptive type of study was conducted in the Cardiology department of Mymensingh Medical College Hospital from October 2017 to March 2019 to investigate the relationship of plasma vitamin D with LVEF in patients with first attack of acute MI. Total 185 patients of first attack of acute MI were included considering inclusion and exclusion criteria. Fasting blood samples were analyzed for plasma vitamin D level. Sample population were grouped at first into two, normal and low vitamin D level, taking 30ng/ml as cut-off value, low vitamin D level is further subdivided into insufficiency (21-29ng/ml), deficiency (10-20ng/ml) and severe deficiency (<10ng/ml). LVEF among the patients was observed. LVEF was found 49.88±8.58% patients having normal vitamin D level (>30ng/ml), 47.60±8.24% of patients having vitamin D insufficiency (21-29ng/ml), 44.38±8.12% of patients having vitamin D deficiency (10-20ng/ml) and 40.61±8.64% patients having severe vitamin D deficiency (<10ng/ml), which was statistically significant (p<0.05). So, low plasma vitamin D level is associated with reduced LVEF in patients hospitalized with first attack of acute MI.

Tunable anomalous Hall conductivity through volume-wise magnetic competition in a topological kagome magnet.

Magnetic topological phases of quantum matter are an emerging frontier in physics and material science. Along these lines, several kagome magnets have appeared as the most promising platforms. Here, we explore magnetic correlations in the kagome magnet Co3Sn2S2. Using muon spin-rotation, we present evidence for competing magnetic orders in the kagome lattice of this compound. Our results show that while the sample exhibits an out-of-plane ferromagnetic ground state, an in-plane antiferromagnetic state appears at temperatures above 90 K, eventually attaining a volume fraction of 80% around 170 K, before reaching a non-magnetic state. Strikingly, the reduction of the anomalous Hall conductivity (AHC) above 90 K linearly follows the disappearance of the volume fraction of the ferromagnetic state. We further show that the competition of these magnetic phases is tunable through applying either an external magnetic field or hydrostatic pressure. Our results taken together suggest the thermal and quantum tuning of Berry curvature induced AHC via external tuning of magnetic order.

Observation of time-reversal-protected single-dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3.

We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3 and their derivatives belong to the Z2 topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi2Te3 is a large spin-orbit-induced indirect bulk band gap (delta approximately 150 meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb2Te3 exhibits similar Z2 topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.

Unconventional scaling of the superfluid density with the critical temperature in transition metal dichalcogenides.

We report on muon spin rotation experiments probing the magnetic penetration depth λ(T) in the layered superconductors in 2H-NbSe2 and 4H-NbSe2. The current results, along with our earlier findings on 1T'-MoTe2 (Guguchia et al.), demonstrate that the superfluid density scales linearly with T c in the three transition metal dichalcogenide superconductors. Upon increasing pressure, we observe a substantial increase of the superfluid density in 2H-NbSe2, which we find to correlate with T c. The correlation deviates from the abovementioned linear trend. A similar deviation from the Uemura line was also observed in previous pressure studies of optimally doped cuprates. This correlation between the superfluid density and T c is considered a hallmark feature of unconventional superconductivity. Here, we show that this correlation is an intrinsic property of the superconductivity in transition metal dichalcogenides, whereas the ratio T c/T F is approximately a factor of 20 lower than the ratio observed in hole-doped cuprates. We, furthermore, find that the values of the superconducting gaps are insensitive to the suppression of the charge density wave state.

Large single crystal growth, transport property, and spectroscopic characterizations of three-dimensional Dirac semimetal Cd3As2.

The three dimensional (3D) Dirac semimetal is a new quantum state of matter that has attracted much attention recently in physics and material science. Here, we report on the growth of large plate-like single crystals of Cd3As2 in two major orientations by a self-selecting vapor growth (SSVG) method, and the optimum growth conditions have been experimentally determined. The crystalline imperfections and electrical properties of the crystals were examined with transmission electron microscopy (TEM), scanning tunneling microscopy (STM), and transport property measurements. This SSVG method makes it possible to control the as-grown crystal compositions with excess Cd or As leading to mobilities near 5-10(5) cm(2)V(-1)s(-1). Zn-doping can effectively reduce the carrier density to reach the maximum residual resistivity ratio (RRRρ300K/ρ5K) of 7.6. A vacuum-cleaved single crystal has been investigated using angle-resolved photoemission spectroscopy (ARPES) to reveal a single Dirac cone near the center of the surface Brillouin zone with a binding energy of approximately 200 meV.

A temporal profile of changes in myocardial manganese after isoprenaline induced cardiac necrosis in albino rats.

Myocardial-necrosis was produced in two groups of albino rats by subcutaneous injection of isoprenaline in doses of 85 mg/kg and 42.5 mg/kg. The necrosis was confirmed by ECG changes, increased serum activities of AspAT, AlAT, GPT and LDH, and by histological examination. Myocardial manganese after isoprenaline administration was estimated over a period of 5 days. The decrease in myocardial manganese was proportional to the extent of cardiac damage. The possible mechanisms and the importance of these changes are discussed.

Effect of lead and zinc administration on liver, kidney and brain levels of copper, lead, manganese and zinc and on erythrocyte ALA-D activity in rats.

Albino male rats were given lead (Pb) and zinc (Zn) orally, singly or in combination, for 14 consecutive days. Liver Pb was increased and liver manganese (Mn) was decreased in animals receiving Pb. The combination of Pb and Zn led to increased Pb and decreased copper (Cu) and Mn. Kidney Zn was increased in rats given Zn or the combination of Pb and Zn. There were no changes in kidney Cu or Mn in any group. Brain Pb levels were significantly increased in animals given Pb and Zn levels in those given Zn. Erythrocytic amino levulinic acid dehydratase (ALA-D) activity was significantly decreased by Pb but not by Pb + Zn.