Anomalies in the Dirac bands in the proximity of correlated electrons.

Dirac fermions, particles with zero rest mass, are observed in topological materials and are believed to play a key role in the exotic phenomena in fundamental science and the advancement of quantum technology. Most of the topological systems studied so far are weakly correlated systems and the study of their properties in the presence of electron correlation is an interesting emerging area of research, where the electron correlation is expected to enhance the effective mass of the particles. Here, we studied the properties of Dirac bands in a non-symmorphic layered Kondo lattice system, CeAgSb, employing high-resolution angle-resolved photoemission spectroscopy and first-principles calculations.

Electronic structure in a transition metal dipnictide TaAs.

The family of transition-metal dipnictides has been of theoretical and experimental interest because this family hosts topological states and extremely large magnetoresistance (MR). Recently,TaAs2, a member of this family, has been predicted to support a topological crystalline insulating state. Here, by using high-resolution angle-resolved photoemission spectroscopy (ARPES), we reveal both closed and open pockets in the metallic Fermi surface (FS) and linearly dispersive bands on the (2‾01) surface, along with the presence of extreme MR observed from magneto-transport measurements.

Quantum metric nonlinear Hall effect in a topological antiferromagnetic heterostructure.

Quantum geometry in condensed-matter physics has two components: the real part quantum metric and the imaginary part Berry curvature. Whereas the effects of Berry curvature have been observed through phenomena such as the quantum Hall effect in two-dimensional electron gases and the anomalous Hall effect (AHE) in ferromagnets, the quantum metric has rarely been explored. Here, we report a nonlinear Hall effect induced by the quantum metric dipole by interfacing even-layered MnBiTe with black phosphorus.

Fluence dependent dynamics of excitons in monolayer MoSiZ(Z = pnictogen).

Reduced dielectric screening in two-dimensional materials enables bound excitons, which modifies their optical absorption and optoelectronic response. Here, we demonstrate the existence of excitons in the bandgap of the monolayer family of the newly discovered syntheticMoSi2Z4(Z=N, P, and As) series of materials. All three monolayers support several bright and strongly bound excitons with binding energies varying from 1 eV to 1.

Axion optical induction of antiferromagnetic order.

Using circularly polarized light to control quantum matter is a highly intriguing topic in physics, chemistry and biology. Previous studies have demonstrated helicity-dependent optical control of chirality and magnetization, with important implications in asymmetric synthesis in chemistry; homochirality in biomolecules; and ferromagnetic spintronics. We report the surprising observation of helicity-dependent optical control of fully compensated antiferromagnetic order in two-dimensional even-layered MnBiTe, a topological axion insulator with neither chirality nor magnetization.

Topology and Symmetry in Quantum Materials.

Interest in topological materials continues to grow unabated in view of their conceptual novelties as well as their potential as platforms for transformational new technologies. Electronic states in a topological material are robust against perturbations and support unconventional electromagnetic responses. The first-principles band-theory paradigm has been a key player in the field by providing successful prediction of many new classes of topological materials.

Laser Irradiation Effect on the p-GaSe/n-HfS PN-Heterojunction for High-Performance Phototransistors.

Two-dimensional (2D)-based PN-heterojunction revealed a promising future of atomically thin optoelectronics with diverse functionalities in different environments. Herein, we reported a p-GaSe/n-HfS van der Waals (vdW) heterostructure for high-performance photodetectors and investigated the laser irradiation effect on the fabricated device. The fabricated 2D vdW heterostructure revealed a high photoresponsivity of 1 × 10 A W with a photocurrent value of 377 nA due to unique type-II band alignment and enhanced surface potential under light illumination, which is further confirmed by density functional theory (DFT) calculations.

Orthorhombic charge density wave on the tetragonal lattice of EuAl.

EuAl possesses the BaAl crystal structure type with tetragonal symmetry 4/. It undergoes a charge density wave (CDW) transition at  = 145 K and features four consecutive antiferromagnetic phase transitions below 16 K. Here we use single-crystal X-ray diffraction to determine the incommensurately modulated crystal structure of EuAl in its CDW state.

Anomalies at the Dirac Point in Graphene and Its Hole-Doped Compositions.

We study the properties of the Dirac states in SiC-graphene and its hole-doped compositions employing angle-resolved photoemission spectroscopy and density functional theory. The symmetry-selective measurements for the Dirac bands reveal their linearly dispersive behavior across the Dirac point which was termed as the anomalous region in earlier studies. No gap is observed even after boron substitution that reduced the carrier concentration significantly from 3.

Superconductivity in Heusler compound ScAuAl.

We report superconducting state properties and electronic structure of a full Heusler material ScAuAl. The resistivity measurement indicates a zero-field (at nominal Earth's field) superconducting transition temperature,= 5.12 K (in contrary to the previously reported value of 4.

Topological Antiferromagnetic Van der Waals Phase in Topological Insulator/Ferromagnet Heterostructures Synthesized by a CMOS-Compatible Sputtering Technique.

Breaking time-reversal symmetry by introducing magnetic order, thereby opening a gap in the topological surface state bands, is essential for realizing useful topological properties such as the quantum anomalous Hall and axion insulator states. In this work, a novel topological antiferromagnetic (AFM) phase is created at the interface of a sputtered, c-axis-oriented, topological insulator/ferromagnet heterostructure-Bi Te /Ni Fe because of diffusion of Ni in Bi Te (Ni-Bi Te ). The AFM property of the Ni-Bi Te interfacial layer is established by observation of spontaneous exchange bias in the magnetic hysteresis loop and compensated moments in the depth profile of the magnetization using polarized neutron reflectometry.

Topological phonons and electronic structure of LiBaSi class of semimetals.

Extension of the topological concepts to the bosonic systems has led to the prediction of topological phonons in materials. Here we discuss the topological phonons and electronic structure of LiBaX (X = Si, Ge, Sn, and Pb) materials using first-principles theoretical modelling. A careful analysis of the phonon spectrum of LiBaX reveals an optical mode inversion with the formation of nodal line states in the Brillouin zone.

Layer Hall effect in a 2D topological axion antiferromagnet.

Whereas ferromagnets have been known and used for millennia, antiferromagnets were only discovered in the 1930s. At large scale, because of the absence of global magnetization, antiferromagnets may seem to behave like any non-magnetic material. At the microscopic level, however, the opposite alignment of spins forms a rich internal structure.

Realization of an intrinsic ferromagnetic topological state in MnBiTe.

Novel magnetic topological materials pave the way for studying the interplay between band topology and magnetism. However, an intrinsically ferromagnetic topological material with only topological bands at the charge neutrality energy has so far remained elusive. Using rational design, we synthesized MnBi8Te13, a natural heterostructure with [MnBiTe] and [BiTe] layers.

Observation of gapped state in rare-earth monopnictide HoSb.

The rare-earth monopnictide family is attracting an intense current interest driven by its unusual extreme magnetoresistance (XMR) property and the potential presence of topologically non-trivial surface states. The experimental observation of non-trivial surface states in this family of materials are not ubiquitous. Here, using high-resolution angle-resolved photoemission spectroscopy, magnetotransport, and parallel first-principles modeling, we examine the nature of electronic states in HoSb.

Magnetotransport properties of noncentrosymmetric CaAgBi single crystal.

We report on the single crystal growth and transport properties of a topological semimetal CaAgBi which crystallizes in the hexagonal ABC-type structure with the non-centrosymmetric space group6(No. 186). The transverse magnetoresistance measurements with current in the basal plane of the hexagonal crystal structure reveal a value of about 30% for∥[10̄0] direction and about 50% for∥[1̅10] direction at 10 K in an applied magnetic field of 14 T.

Spontaneous gyrotropic electronic order in a transition-metal dichalcogenide.

Chirality is ubiquitous in nature, and populations of opposite chiralities are surprisingly asymmetric at fundamental levels. Examples range from parity violation in the subatomic weak force to homochirality in biomolecules. The ability to achieve chirality-selective synthesis (chiral induction) is of great importance in stereochemistry, molecular biology and pharmacology.

Discovery of topological Weyl fermion lines and drumhead surface states in a room temperature magnet.

Topological matter is known to exhibit unconventional surface states and anomalous transport owing to unusual bulk electronic topology. In this study, we use photoemission spectroscopy and quantum transport to elucidate the topology of the room temperature magnet CoMnGa. We observe sharp bulk Weyl fermion line dispersions indicative of nontrivial topological invariants present in the magnetic phase.

Spin-dependent scattering induced negative magnetoresistance in topological insulator BiTe nanowires.

Studies of negative magnetoresistance in novel materials have recently been in the forefront of spintronic research. Here, we report an experimental observation of the temperature dependent negative magnetoresistance in BiTe topological insulator (TI) nanowires at ultralow temperatures (20 mK). We find a crossover from negative to positive magnetoresistance while increasing temperature under longitudinal magnetic field.

Porcupine gnaw marks on a Late Pliocene bone from the Upper Siwaliks exposed near Village Khetpurali (Haryana, India).

Bone accumulation by porcupines at archaeological sites is well known. However, in paleontological sites such a taphonomical occurrence is rather rare. We here report porcupine (Hystrix sp.

Stature estimation from different combinations of foot measurements using linear and multiple regression analysis in a North Indian male population.

Establishing the identity of the deceased is the most important task for forensic anthropologists in forensic case-work involving unidentified human remains. In such cases, forensic anthropologists examine the remains to derive the biological profile of the deceased i.e.

Topological Hourglass Dirac Semimetal in the Nonpolar Phase of Ag_{2}BiO_{3}.

Materials with tunable charge and lattice degrees of freedom provide excellent platforms for investigating multiple phases that can be controlled via external stimuli. We show how the charge-ordered ferroelectric oxide Ag_{2}BiO_{3}, which has been realized experimentally, presents a unique exemplar of a metal-insulator transition under an external electric field. Our first-principles calculations, combined with a symmetry analysis, reveal the presence of a nearly ideal hourglass-Dirac-semimetal state in the nonpolar structure of Ag_{2}BiO_{3}.

Reproduction of the Charge Density Wave Phase Diagram in 1T-TiSe_{2} Exposes its Excitonic Character.

Recent experiments suggest that excitonic degrees of freedom play an important role in precipitating the charge density wave (CDW) transition in 1T-TiSe_{2}. Through systematic calculations of the electronic and phonon spectrum based on density functional perturbation theory, we show that the predicted critical doping of the CDW phase overshoots the experimental value by 1 order of magnitude. In contrast, an independent self-consistent many-body calculation of the excitonic order parameter and renormalized band structure is able to capture the experimental phase diagram in extremely good qualitative and quantitative agreement.