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Two-dimensional (2D) Dirac materials, e.g., graphene and transition metal dichalcogenides (TMDs), are one-atom-thick monolayers whose electronic behaviors are described by the Dirac equation. These materials serve not only as test beds for novel quantum physics but also as promising constituents for nanophotonic devices. This review provides a brief overview of the recent effort to control Dirac electron behaviors using nanophotonics. We introduce a principle of light-2D Dirac matter interaction to offer a design guide for 2D Dirac material–based nanophotonic devices. We also discuss opportunities for coupling nanophotonics with externally perturbed 2D materials. [ABSTRACT FROM AUTHOR]

Herein, we investigate the effect of tilt mismatch on the quantum oscillations of spin transport properties in two-dimensional asymmetrically tilted Dirac cone systems. This study involves the examination of conductance oscillation in two distinct junction types: transverse- and longitudinal-tilted Dirac cones (TTDCs and LTDCs). Our findings reveal an unusual quantum oscillation of spin-polarized conductance within the TTDC system, characterized by two distinct anomaly patterns within a single period, labeled as the linear conductance phase and the oscillatory conductance phase. Interestingly, these phases emerge in association with tilt-induced orbital pseudo-magnetization and exchange interaction. Our study also demonstrates that the structure of the LTDC can modify the frequency of spin conductance oscillation, and the asymmetric effect within this structure results in a quantum beating pattern in oscillatory spin conductance. We note that an enhancement in the asymmetric longitudinal tilt velocity ratio within the structure correspondingly amplifies the beating frequency. Our research potentially contributes valuable insights for detecting the asymmetry of tilted Dirac fermions in type-I Dirac semimetal-based spintronics and quantum devices. [ABSTRACT FROM AUTHOR]

The complex theoretical analysis of the density of states, band structures, and Fermi surfaces, based on predictions of the density functional theory methods, unveils the unique electronic properties of the LaZn1−xBi2 system. In this paper, the Zn vacancies (for x = 0.5 ) were modeled using a modified unit cell of lower symmetry than that for a fully stoichiometric one (for x = 0 ). The existence of several Dirac-like features in the electronic band structures was found. Some of them were found to be intimately associated with the nonsymmorphic symmetry of the system, and these were investigated in detail. The calculated Fermi surface shapes, as well as the Fermi velocity values (up to ∼1.2 × 10 6 m/s), are in good agreement with other analogous square-net Dirac semimetals. The combination of charge-carrier uncompensation, relatively small band splitting, and the tolerance factor for square-net semimetals t ≤ 0.95 for LaZn0.5Bi2, constitutes a very promising indicator of the topological features of this system, warranting further experimental studies. [ABSTRACT FROM AUTHOR]

The concept of torsion in geometry, although known for a long time, has not gained considerable attention from the physics community until relatively recently, due to its diverse and potentially important applications to a plethora of contexts of physical interest. These range from novel materials, such as graphene and graphene-like materials, to advanced theoretical ideas, such as string theory and supersymmetry/supergravity, and applications thereof in terms of understanding the dark sector of our Universe. This work reviews such applications of torsion at different physical scales. [ABSTRACT FROM AUTHOR]

Herein, the electronic, thermoelectric, and optical properties of semimetallic HPX6 (X = C, Si, Ge, Sn) monolayers are systematically studied under the influence of external electric field in the framework of density functional theory. A band tuning has been achieved in these structures by the application of an external electric field of appropriate strength. It is predicted that Dirac cone splitting is nearly proportional to the external electric field strength. The modulation of electric properties induced by external field can alter the position of chemical potential in the band diagram and brings significant improvement in thermoelectric responses. The application of an external electric field significantly modulates the optical properties. The electric field‐induced HPX6 system provides better thermoelectric and optical response for nanodevice applications. [ABSTRACT FROM AUTHOR]

Herein, we investigate the effect of tilt mismatch on the quantum oscillations of spin transport properties in two-dimensional asymmetrically tilted Dirac cone systems. This study involves the examination of conductance oscillation in two distinct junction types: transverse- and longitudinal-tilted Dirac cones (TTDCs and LTDCs). Our findings reveal an unusual quantum oscillation of spin-polarized conductance within the TTDC system, characterized by two distinct anomaly patterns within a single period, labeled as the linear conductance phase and the oscillatory conductance phase. Interestingly, these phases emerge in association with tilt-induced orbital pseudo-magnetization and exchange interaction. Our study also demonstrates that the structure of the LTDC can modify the frequency of spin conductance oscillation, and the asymmetric effect within this structure results in a quantum beating pattern in oscillatory spin conductance. We note that an enhancement in the asymmetric longitudinal tilt velocity ratio within the structure correspondingly amplifies the beating frequency. Our research potentially contributes valuable insights for detecting the asymmetry of tilted Dirac fermions in type-I Dirac semimetal-based spintronics and quantum devices.

In this work we analyze the statistical thermodynamic functions and magnetic moment of a Dice lattice subject to a normal quantizing magnetic field. Our analysis addresses the Grand Potential and Helmholtz Free Energy, as well as the magnetic moment, entropy and specific heat at constant volume, explicitly determining their magnetic field dependencies in the degenerate statistical regime, replete with de Haas-van Alphen oscillatory phenomenology (and other magnetic field dependence); and also determining their temperature dependencies jointly with magnetic field features in the approach to the zero temperature limit. Furthermore, we evaluate the Grand Potential exactly, for arbitrary temperature and density. Our results are obtained with consideration of the presence of heat and particle baths with fixed chemical potential and they are discussed in relation to other pertinent work on the subject.

We examine the question “Can Dirac materials exist in a nondegenerate statistical state?,” deriving and employing an identity for the thermodynamic Grand Potential $\Omega$ (per unit volume/area) in the low density nondegenerate statistical regime, relating it to the density $n$ as $\Omega = -\beta ^{-1} n$ ($\beta ^{-1} = \kappa _{B} T$ is thermal energy, $\kappa _{B}$ is the Boltzmann constant, and $T$ is Kelvin temperature). The implications of this identity for Dirac materials are explored. The identity is universally valid for all thermodynamic systems in equilibrium in the nondegenerate, low density statistical regime, irrespective of size, dimensionality or applied static fields. Phenomena that may contribute to the realization of such a nondegenerate statistical equilibrium state in Dirac materials are discussed.

The third harmonic generation (THG) of graphite layers on paper substrate upon excitation with intense (up to 100 kV cm−1) narrowband terahertz (THz) pulses is studied. Highest THG efficiencies are comparable with those of chemical vapor deposition‐grown single‐layer graphene. Samples are hand drawn, using commercially available pencils. The THG response shows high sensitivity regarding the hatching direction relative to the THz polarization orientation. Using Raman spectroscopy, the occurrence of graphene‐like structures in the samples is confirmed. The findings demonstrate the feasibility of virtually no‐cost and easy‐to‐fabricate materials for THz nonlinear optics.

The complex theoretical analysis of the density of states, band structures, and Fermi surfaces, based on predictions of the density functional theory methods, unveils the unique electronic properties of the LaZn1−xBi2 system. In this paper, the Zn vacancies (for x=0.5) were modeled using a modified unit cell of lower symmetry than that for a fully stoichiometric one (for x=0). The existence of several Dirac-like features in the electronic band structures was found. Some of them were found to be intimately associated with the nonsymmorphic symmetry of the system, and these were investigated in detail. The calculated Fermi surface shapes, as well as the Fermi velocity values (up to ∼1.2 ×106 m/s), are in good agreement with other analogous square-net Dirac semimetals. The combination of charge-carrier uncompensation, relatively small band splitting, and the tolerance factor for square-net semimetals t≤0.95 for LaZn0.5Bi2, constitutes a very promising indicator of the topological features of this system, warranting further experimental studies.

The concept of torsion in geometry, although known for a long time, has not gained considerable attention from the physics community until relatively recently, due to its diverse and potentially important applications to a plethora of contexts of physical interest. These range from novel materials, such as graphene and graphene-like materials, to advanced theoretical ideas, such as string theory and supersymmetry/supergravity, and applications thereof in terms of understanding the dark sector of our Universe. This work reviews such applications of torsion at different physical scales.

Superconductivity becomes more interesting when it encounters dimensional constraint or topology because it is of importance for exploring exotic quantum phenomena or developing superconducting electronics. Here, the coexistence of naturally formed surface superconducting state and 3D topological Dirac state in single crystals of BaMg2Bi2 is reported. The electronic structure obtained from the first‐principles calculations demonstrates that BaMg2Bi2 is an ideal Dirac material, in which the Dirac point is very close to the Fermi level and no other energy band crosses the Fermi level. Superconductivity up to 4.77−−5.17 K can be observed under ambient pressure in the measurements of resistivity. The anisotropic upper critical field and angle dependent magnetoresistance reveals the 2D characteristic of superconductivity, indicating that superconductivity occurs on the surface of the sample and is absent in the bulk state. The study not only provides BaMg2Bi2 as a suitable platform to study the interplay between superconductivity and topological Dirac state but also indicates that MgBi‐based materials may be a promising system for exploring new superconductors. [ABSTRACT FROM AUTHOR]

We experimentally investigated charge transport through a single planar junction between a NiTe 2 Dirac semimetal and a normal gold lead. At milli-Kelvin temperatures, we observe non-Ohmic d V / d I (V) behavior resembling Andreev reflection at a superconductor–normal metal interface, while NiTe 2 bulk remains non-superconducting. The conclusion on superconductivity is also supported by the suppression of the effect by temperature and magnetic field. In analogy with the known results for Cd 3 As 2 Dirac semimetal, we connect this behavior with interfacial superconductivity due to the flat-band formation at the Au-NiTe 2 interface. Since the flat-band and topological surface states are closely connected, the claim on the flat-band-induced superconductivity is also supported by the Josephson current through the topological surface states on the pristine NiTe 2 surface. We demonstrate the pronounced Josephson diode effect, which results from the momentum shift of the topological surface states of NiTe 2 under an in-plane magnetic field. [ABSTRACT FROM AUTHOR]

We work with photonic graphene lattices under strain with gain and loss, modeled by the Dirac equation with an imaginary mass term. To construct such Hamiltonians and their solutions, we use the free-particle Dirac equation and then a matrix approach of supersymmetric quantum mechanics to generate a new Hamiltonian with a magnetic vector potential and an imaginary position-dependent mass term. Then, we use a gauge transformation that maps our solutions to the final system, photonic graphene under strain with a position-dependent gain/loss term. We give explicit expressions for the guided modes.

Analogs of fundamental physical phenomena can be used in two ways. One way consists in reproducing specific aspects of the classical or quantum gravity of quantum fields in curved space or of other high-energy scenarios on lower-energy corresponding systems. The "reverse way" consists in building fundamental physical theories, for instance, quantum gravity models, inspired by the lower-energy corresponding systems. Here, we present the case of graphene and other Dirac materials. [ABSTRACT FROM AUTHOR]

Using both first principles and analytical approaches, we investigate the role of a transverse electric field in tuning the electrical, thermoelectric, optical and transport properties of a buckled tetragonal silicene (TS) structure. The transverse electric field transforms the linear spectrum to parabolic at the Fermi level and opens a band gap. The gap is similar at the two Dirac points present in the irreducible Brillouin zone of the TS structure and increases in proportion to the applied field strength. However, a sufficiently strong electric field converts the system into a metallic one. A comparable band opening is also seen in the TS nanoribbons. Electric field-induced semiconducting nature improves its thermoelectric properties. Estimated Debye temperature reveals its superiority over graphene in terms of thermoelectric performance. The optical response of the structures is very asymmetric. Large values of imaginary and real components of the dielectric function are seen. The absorption frequency lies in the UV region. Plasma frequencies are identified and are red-shifted with the applied field. The current-voltage characteristics of the symmetric type nanoribbons show oscillation in current whereas the voltage-rectifying capability of anti-symmetric type nanoribbons under a transverse electric field is interesting., (© 2024 IOP Publishing Ltd.)

We experimentally investigated charge transport through a single planar junction between a NiTe2 Dirac semimetal and a normal gold lead. At milli-Kelvin temperatures, we observe non-Ohmic dV/dI(V) behavior resembling Andreev reflection at a superconductor–normal metal interface, while NiTe2 bulk remains non-superconducting. The conclusion on superconductivity is also supported by the suppression of the effect by temperature and magnetic field. In analogy with the known results for Cd3As2 Dirac semimetal, we connect this behavior with interfacial superconductivity due to the flat-band formation at the Au-NiTe2 interface. Since the flat-band and topological surface states are closely connected, the claim on the flat-band-induced superconductivity is also supported by the Josephson current through the topological surface states on the pristine NiTe2 surface. We demonstrate the pronounced Josephson diode effect, which results from the momentum shift of the topological surface states of NiTe2 under an in-plane magnetic field.

Analogs of fundamental physical phenomena can be used in two ways. One way consists in reproducing specific aspects of the classical or quantum gravity of quantum fields in curved space or of other high-energy scenarios on lower-energy corresponding systems. The “reverse way” consists in building fundamental physical theories, for instance, quantum gravity models, inspired by the lower-energy corresponding systems. Here, we present the case of graphene and other Dirac materials.

We propose a novel class of two-dimensional (2D) Dirac materials in the MX family (M = Be, Mg, Zn and Cd, X = Cl, Br and I), which exhibit graphene-like band structures with linearly-dispersing Dirac-cone states over large energy scales (0.8–1.8 eV) and ultra-high Fermi velocities comparable to graphene. Spin-orbit coupling opens sizable topological band gaps so that these compounds can be effectively classified as quantum spin Hall insulators. The electronic and topological properties are found to be highly tunable and amenable to modulation via anion-layer substitution and vertical electric field. Electronic structures of several members of the family are shown to host a Van-Hove singularity (VHS) close to the energy of the Dirac node. The enhanced density-of-states associated with these VHSs could provide a mechanism for inducing topological superconductivity. The presence of sizable band gaps, ultra-high carrier mobilities, and small effective masses makes the MX family promising for electronics and spintronics applications. [ABSTRACT FROM AUTHOR]

Electronic properties of the LaSb2 superconductor and its non-superconducting LaAgSb2 analogue are determined within the density functional theory approach. The existence of 2D Dirac fermions in the bulk electronic structure of both compounds is unveiled and analysed based on weighted bands calculated around the Fermi level. Interestingly, a lack of superconductivity in LaAgSb2 can be explained in terms of the topological Feshbach shape resonance of some Fermi surface sheets, associated with the reduction of their dimensionality (from 3D to 2D). [ABSTRACT FROM AUTHOR]

Electronic properties of the LaSb2 superconductor and its non-superconducting LaAgSb2 analogue are determined within the density functional theory approach. The existence of 2D Dirac fermions in the bulk electronic structure of both compounds is unveiled and analysed based on weighted bands calculated around the Fermi level. Interestingly, a lack of superconductivity in LaAgSb2 can be explained in terms of the topological Feshbach shape resonance of some Fermi surface sheets, associated with the reduction of their dimensionality (from 3D to 2D). [ABSTRACT FROM AUTHOR]

Electronic devices that operate at terahertz frequencies will require new materials that exhibit higher carrier velocities than traditional semiconductors. Calculations show that cadmium arsenide, a 3D topological (Dirac) semimetal, is an excellent candidate for field effect transistors that operate at frequencies above 1 THz. Moreover, such transistors have unique advantages that are enabled by the properties of Dirac electrons. These include predictions of an unprecedented linearity of the transconductance and cutoff frequencies over a large operating range and cutoff frequencies that remain above 1 THz at carrier densities as low as 1011 cm−2. The calculations are underpinned by measurements of devices with cadmium arsenide channels. Extremely low contact resistances (<2 × 10−9 Ω cm2), high electron velocities (>7 × 105 m s−1), and unprecedentedly large current densities (up to 10 A mm−1) are demonstrated. Current modulation (>50%) and transconductance already achieved in the early transistors show the potential for large (>10 ×) improvements by reducing interface trap densities. The results demonstrate the significant potential of topological semimetals for high‐speed transistors operating in the THz regime and open up new opportunities for next‐generation RF circuits. [ABSTRACT FROM AUTHOR]

We studied the broadband optical conductivity of CaMnBi2, a material with two-dimensional Dirac electronic bands, and found that both components of the intraband conductivity follow a universal power law as a function of frequency at low temperatures. This conductivity scaling differs from the Drude(-like) behavior, generally expected for free carriers, but matches the predictions for the intraband response of an electronic system in a quantum critical region. Since no other indications of quantum criticality are reported for CaMnBi2 so far, the cause of the observed unusual scaling remains an open question.

Discrete-scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity that can be rarely observed in quantum systems. Here, we report the log-periodic quantum oscillations in the longitudinal magnetoresistivity (ρxx) and the Hall traces (ρyx) of HfTe5 crystals, which reveal the DSI in the transport-coefficients matrix. The oscillations in ρxx and ρyx show the consistent log B -periodicity with a phase shift. The finding of the log B oscillations in the Hall resistance supports the physical mechanism as a general quantum effect originating from the resonant scattering. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. This work evidences the universality of the DSI in the Dirac materials and provides indispensable information for a full understanding of this novel phenomenon. [ABSTRACT FROM AUTHOR]

Discrete-scale invariance (DSI) is a phenomenon featuring intriguing log-periodicity that can be rarely observed in quantum systems. Here, we report the log-periodic quantum oscillations in the longitudinal magnetoresistivity (ρxx) and the Hall traces (ρyx) of HfTe5 crystals, which reveal the DSI in the transport-coefficients matrix. The oscillations in ρxx and ρyx show the consistent log B -periodicity with a phase shift. The finding of the log B oscillations in the Hall resistance supports the physical mechanism as a general quantum effect originating from the resonant scattering. Combined with theoretical simulations, we further clarify the origin of the log-periodic oscillations and the DSI in the topological materials. This work evidences the universality of the DSI in the Dirac materials and provides indispensable information for a full understanding of this novel phenomenon. [ABSTRACT FROM AUTHOR]

We consider the problem of confining the famously elusive Dirac-like quasiparticles, as found in some recently discovered low-dimensional systems. After briefly surveying the existing theoretical proposals for creating bound states in Dirac materials, we study relativistic excitations with a position-dependent mass term. With the aid of an exactly-solvable model, we show how bound states begin to emerge after a critical condition on the size of the mass term is met. We also reveal some exotic properties of the unusual confinement discovered, including an elegant chevron structure of the bound state energies as a function of the size of the mass. [ABSTRACT FROM AUTHOR]

It is shown that phase-space Fisher information marks topological phase transitions in 2D Dirac gapped materials. The phase-space Fisher information determined for electrons and holes exhibit minimum at the charge neutrality points. Topological quantum numbers are defined to identify different phases utilizing combined information measures. Upper and lower bounds are derived for the phase-space Fisher information. [ABSTRACT FROM AUTHOR]

Abstract We investigate the physical properties of massive Dirac fermions in SrMnSb 2 using transport, specific heat, electronic structure calculations, and Shubnikov-de Haas (SdH) oscillations. SrMnSb 2 is a candidate Dirac antiferromagnet, consisting of the MnSb layers and the distorted square net of Sb atoms with a zigzag chain structure. This structural distortion leads to gap opening at the band crossing point found in the square lattice of the sister compound SrMnBi 2 but leaves another Dirac band crossing near the Brillouin zone boundary. The small 2D Fermi surface with a light electron mass and a small Fermi energy is confirmed by the large resistivity anisotropy, the large Seebeck coefficient, and also the angle and temperature dependent SdH oscillations. The Berry phase obtained from the SdH oscillations is trivial, in contrast to the case of SrMnBi 2. The relatively large spin orbit coupling gap and the small Fermi energy in SrMnSb 2 is found to be essential to understand this contrasting behavior of the massive Dirac fermions as compared to SrMnBi 2. Our observations demonstrate that the Berry phase of the mobile electrons in SrMnSb 2 is sensitive to the Fermi level change and can be tuned by doping or deficiency. Highlights • A small Fermi surface of SrMnSb 2 is confirmed by Shubnikov-de Haas oscillations. • The Berry phase from quantum oscillations is found to be nearly zero in SrMnSb 2. • SrMnSb 2 hosts massive Dirac fermions due to the spin-orbit coupling. [ABSTRACT FROM AUTHOR]

On the basis of the continuum model for long-wavelength charge carriers, originating in the tight-binding approximation for the nearest-neighbour interaction of atoms in the crystalline lattice, we consider quantum ground-state effects of electronic excitations in Dirac materials with two-dimensional monolayer honeycomb structures warped into nanocones by a disclination; the nonzero size of the disclination is taken into account, and a boundary condition at the edge of the disclination is chosen to ensure self-adjointness of the Dirac–Weyl Hamiltonian operator. We show that the quantum ground-state effects are independent of the disclination size and find circumstances when they are independent of a parameter of the boundary condition. The magnetic flux circulating in the angular direction around the nanocone apex and the pseudomagnetic flux directed orthogonally to the nanocone surface are shown to be induced in the ground state. [ABSTRACT FROM AUTHOR]

The graphene family of 2D-Dirac materials shows different topological phases induced by the application of electric fields and the circularly polarized lasers. In this paper we present an informational analysis of these topological phases. Additionally, we determine the entropic uncertainty of these systems in the plane given by the electric and light fields, showing the different topological phases. [ABSTRACT FROM AUTHOR]

A Dirac metal is a doped (gated) Dirac material with the Fermi energy (E F) lying either in the conduction or valence bands. In the non-interacting picture, optical absorption in gapless Dirac metals occurs only if the frequency of incident photons (Ω) exceeds the direct (Pauli) frequency threshold, equal to 2 E F . In this work, we study, both analytically and numerically, the role of electron–electron (ee) and electron–hole (eh) interactions in optical absorption of two-dimensional (2D) and three-dimensional (3D) Dirac metals in the entire interval of frequencies below 2 E F . We show that, for Ω ≪ E F , the optical conductivity, ℜ σ (Ω) , arising from the combination of ee and certain eh scattering processes, scales as Ω 2 ln Ω in 2D and as Ω 2 in 3D, respectively, both for short-range (Hubbard) and long-range (screened Coulomb) interactions. Another type of eh processes, similar to Auger–Meitner (AM) processes in atomic physics, starts to contribute for Ω above the direct threshold, equal to E F. Similar to the case of doped semiconductors with parabolic bands studied in prior literature, the AM contribution to ℜ σ (Ω) in Dirac metals is manifested by a threshold singularity, ℜ σ (Ω) ∝ (Ω − E F) d + 2 , where d is the spatial dimensionality and 0 < Ω − E F ≪ E F . In contrast to doped semiconductors, however, the AM contribution in Dirac metals is completely overshadowed by the ee and other eh contributions. Numerically, ℜ σ (Ω) happens to be small in almost the entire range of Ω < 2 E F . This finding may have important consequences for collective modes in Dirac metals lying below 2 E F . [ABSTRACT FROM AUTHOR]

We investigated magneto-optical response of undoped Bi2Te3 films in the terahertz frequency range (0.3–5.1 THz, 10–170 cm−1) in magnetic fields up to 10 T. The optical transmission, measured in the Faraday geometry, is dominated by a broad Lorentzian-shaped mode, whose central frequency linearly increases with applied field. In zero field, the Lorentzian is centered at zero frequency, representing hence the free-carrier Drude response. We interpret the mode as a cyclotron resonance (CR) of free carriers in Bi2Te3. Because the mode’s frequency position follows a linear magnetic-field dependence and because undoped Bi2Te3 is known to possess appreciable number of bulk carriers, we associate the mode with a bulk CR. In addition, the cyclotron mass obtained from our measurements fits well the literature data on the bulk effective mass in Bi2Te3. Interestingly, the width of the CR mode demonstrates a behavior non-monotonous in field. We propose that the CR width is defined by two competing factors: impurity scattering, which rate decreases in increasing field, and electron-phonon scattering, which exhibits the opposite behavior.

Mid- and near-infrared measurements reveal that the optical conductivity of the three-dimensional topological insulator, Bi2Te2Se, is dominated by bulk carriers and shows a linear-in-frequency increase at 0.5 to 0.8 eV. This linearity might be interpreted as a signature of three-dimensional (bulk) Dirac bands; however, band-structure calculations show that transitions between bands with complex dispersion contribute instead to the inter-band optical conductivity at these frequencies and, hence, the observed linearity is accidental. These results warn against the oversimplified interpretations of optical-conductivity measurements in different Dirac materials.

In the present study, a novel and unconventional two-dimensional (2D) material with Dirac electronic features has been designed using sulflower with the help of density functional theory methods and first principles calculations. This 2D material comprises of hetero atoms (C, S) and belongs to the tetragonal lattice with P 4 /nmm space group. Scrutiny of the results show that the 2D nanosheet exhibits a nanoporous wave-like geometrical structure. Quantum molecular dynamics simulations and phonon mode analysis emphasize the dynamical and thermal stability. The novel 2D nanosheet is an auxetic material with an anisotropy in the in-plane mechanical properties. Both composition and geometrical features are completely different from the conditions necessary for the formation of Dirac cones in graphene. However, the presence of semi-metallic nature, linear band dispersion relation, massive fermions and massless Dirac fermions are observed in the novel 2D nanosheet. The massless Dirac fermions exhibit highly isotropic Fermi velocities (v f =0.68×10 6  m/s) along all crystallographic directions. The zero-band gap semi metallic features of the novel 2D nanosheet are perturbative to the electric field and external strain., (© 2023 Wiley-VCH GmbH.)

Graphical abstract Highlights • Weak electron-phonon coupling, λ ep , is obtained for LaTESb 2 superconductors. • No clear relation between λ ep , DOS at E F , and T C in this 112-family is found. • Dirac-like bands are revealed near the Fermi level in particular for LaCuSb 2. • Quasi-2D Fermi surface sheets are connected with the Dirac-like bands. • Dirac-like bands are plausible cause of almost linear magnetoresistance curves. Abstract Electronic structures of LaNiSb 2 , LaCuSb 2 , and LaPdSb 2 compounds are studied with the fully relativistic density functional theory methods. The detailed analysis of the densities of states, band structures, and Fermi surfaces allows an explanation of some intriguing transport properties of these materials. The calculated Sommerfeld coefficients are in good agreement with the experimental data, although the values of electron-phonon coupling estimated here are relatively low. All studied compounds exhibit Dirac-like bands in the vicinity of the Fermi level and two-dimensional character of some Fermi surface sheets. [ABSTRACT FROM AUTHOR]

Ballistically propagating topologically protected states harbor exotic transport phenomena of wide interest. Here we describe a nontopological mechanism that produces such states at the surfaces of generic Dirac materials, giving rise to propagating surface modes with energies near the bulk band crossing. The robustness of surface states originates from the unique properties of Dirac--Bloch wavefunctions which exhibit strong coupling to generic boundaries. Surface states, described by Jackiw--Rebbitype bound states, feature a number of interesting properties. Mode dispersion is gate tunable, exhibiting a wide variety of different regimes, including nondispersing flat bands and linear crossings within the bulk bandgap. The ballistic wavelike character of these states resembles the properties of topologically protected states; however, it requires neither topological restrictions nor additional crystal symmetries. The Dirac surface states are weakly sensitive to surface disorder and can dominate edge transport at the energies near the Dirac point. [ABSTRACT FROM AUTHOR]

Quasiparticles with Dirac-type dispersion can be observed in nearly gapless bulk semiconductors alloys in which the bandgap is controlled through the material composition. We demonstrate that the Dirac dispersion can be realized in short-period InAs1-xSbx/InAs1-ySby metamorphic superlattices with the bandgap tuned to zero by adjusting the superlattice period and layer strain. The new material has anisotropic carrier dispersion: the carrier energy associated with the in-plane motion is proportional to the wave vector and characterized by the Fermi velocity vF, and the dispersion corresponding to the motion in the growth direction is quadratic. Experimental estimate of the Fermi velocity gives vF = 6.7 x 105 m/s. Remarkably, the Fermi velocity in this system can be controlled by varying the overlap between electron and hole states in the superlattice. Extreme design flexibility makes the short-period metamorphic InAs1-xSbx/InAs1-ySby superlattice a new prospective platform for studying the effects of charge-carrier chirality and topologically nontrivial states in structures with the inverted bandgaps. [ABSTRACT FROM AUTHOR]

New topological quantum numbers are introduced by analyzing complexity measures and relative Rényi entropies in silicene in the presence of perpendicular electric and magnetic fields. These topological quantum numbers characterize the topological insulator and band insulator phases in silicene. In addition, we have found that, these information measures reach extremum values at the charge neutrality points. These results are valid for other 2D gapped Dirac materials analogous to silicene with a buckled honeycomb structure and a significant spin-orbit coupling. [ABSTRACT FROM AUTHOR]

We show that a wide class of quantum systems with translational invariance can host dispersionless, soliton-like, wave packets. We focus on the setting where the effective, two-dimensional Hamiltonian acquires the form of the Dirac operator. The proposed framework for construction of the dispersionless wave packets is illustrated on silicene-like systems with topologically nontrivial effective mass. Our analytical predictions are accompanied by a numerical analysis and possible experimental realizations are discussed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electronic structure of a series of graphene-borophene lateral heterostructures is reported. • They are structurally stable and exhibit mechanical anisotropy with a negative Poisson's ratio. • The lateral heterostructures are classified as either semimetals or metals. • Show potential candidacy as electrode for Li-ion batteries with high storage capacity. Covalent stitching of dissimilar semi-infinite two-dimensional (2D) nanosheets as the lateral heterostructures is relatively rare due to the various challenges involved in the experimental synthesis. In this study, we have integrated the graphene and borophene monolayers and created a series of lateral heterostructures inspired by their recent experimental synthesis. Further, we have systematically explored the geometrical, thermal, mechanical properties and electronic structure of these lateral heterostructures using the density functional theory calculations. Results authenticate that graphene and borophene lateral heterostructures (GBLHs) are dynamically and thermally stable. Further, they exhibit anisotropic mechanical properties including the negative Poisson's ratio. Electronic structure calculations reveal that the GBLHs can be classified as either semi-metals or metals and the conductivity depending on the width of the graphene and borophene chains comprises the heterostructure. Further, massless Dirac fermions and anisotropic high hole and electron mobilities are the prominent electronic features of the semi-metallic GBLHs. Finally, we have investigated the application potentials of GBLHs as the anode materials for lithium-ion rechargeable batteries (LIBs). Computed results illustrate that the GBLHs can serve as potential anode materials in the LIBs with intriguing features like metallicity, optimal adsorption energies, low diffusion barrier, enhanced specific storage capacity (1394.5 mA h g−1) and an average open circuit voltage (∼0.52 eV). [ABSTRACT FROM AUTHOR]