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The prevalence of and mortality associated with methamphetamine use cause a concern. To add insights regarding the mechanisms that drive the disease progression, we investigated the relationship between cigarette smoking initiation and methamphetamine addiction severity as well as the role of trait impulsivity in methamphetamine use disorder (MUD). Nine hundred and fifty-three patients with MUD treated between January 2016 and December 2018 were included. Trait impulsivity and methamphetamine addiction severity were evaluated using the Barratt Impulsiveness Scale, 11th version (BIS-11) and Kreek–McHugh–Schluger–Kellogg scale (KMSK), respectively. Data were analyzed through univariate linear regression and mediation analysis by using the CAUSALMED procedure. The median age of 953 patients was 37 years (interquartile range, 30–43 years), and 93.1% of them had smoking history. The KMSK score was significantly associated with age at cigarette smoking initiation and BIS-11 score (b = − 0.07, P <.001 and b = 0.057, P <.001, respectively). The mediation analysis revealed a negative total effect (estimate = − 0.06, 95% CI − 0.097 to − 0.023), a negative natural direct effect (estimate = − 0.048, 95% CI − 0.086 to − 0.011) of age at cigarette smoking initiation on KMSK score, and a negative natural indirect effect (estimate = − 0.012, 95% CI − 0.019 to − 0.004) by the BIS total score, accounting for 19.41% of the total effect. Earlier cigarette smoking initiation was associated with higher methamphetamine addiction severity through the possible mediating effect of trait impulsivity. Early cigarette smoking initiation could be viewed as a vulnerable phenotype that needs more prevention effort, and trait impulsivity might be a key treatment focus worth integrating into psychosocial interventions for both adolescent cigarette smokers and adult patients with MUD due to its mediating effect. [ABSTRACT FROM AUTHOR]

Proposed mechanisms for large intrinsic anomalous Hall effect (AHE) in magnetic topological semimetals include diverging Berry curvatures of Weyl nodes, anticrossing nodal rings or points of non-trivial bands. Here we demonstrate that a half-topological semimetal (HTS) state near a topological critical point can provide an alternative mechanism for a large AHE via systematic studies on an antiferromagnetic (AFM) half-Heusler compound TbPdBi. We not only observe a large AHE with tanΘH ≈ 2 in its field-driven ferromagnetic (FM) phase, but also find a distinct Hall resistivity peak in its canted AFM phase. Moreover, we observe a large negative magnetoresistance with a value of ~98%. Our in-depth theoretical modelling indicates that these exotic transport properties originate from the HTS state which exhibits Berry curvature cancellation between the trivial spin-up and nontrivial spin-down bands. Our study offers alternative strategies for improved materials design for spintronics and other applications. The emergence of large intrinsic anomalous Hall effect (AHE) is tied to the Berry curvature in magnetic topological semimetals, but other alternatives to achieve AHE are still desirable. The authors show that a half-topological semimetal state provides an alternative platform for driving AHE and exhibits a nearly isotropic negative magnetoresistance. [ABSTRACT FROM AUTHOR]

Nontrivial band topologies in semimetals lead to robust surface states that can contribute dominantly to the total conduction. This may result in reduced resistivity with decreasing feature size contrary to conventional metals, which may highly impact the semiconductor industry. Here we study the resistivity scaling of a representative topological semimetal CoSi using realistic band structures and Green's function methods. We show that there exists a critical thickness dc dividing different scaling trends. Above dc, when the defect density is low such that surface conduction dominates, resistivity reduces with decreasing thickness; when the defect density is high such that bulk conduction dominates, resistivity increases as in conventional metals. Below dc where bulk states are depopulated, the persistent Fermi-arc remnant states give rise to decreasing resistivity down to the ultrathin limit, unlike topological insulators. The observed CoSi scaling can apply to broad classes of topological semimetals, providing guidelines for materials screening in back-end-of-line interconnect applications. [ABSTRACT FROM AUTHOR]

In one-dimensional (1D) systems, electronic interactions lead to a breakdown of Fermi liquid theory and the formation of a Tomonaga-Luttinger Liquid (TLL). The strength of its many-body correlations can be quantified by a single dimensionless parameter, the Luttinger parameter K, characterising the competition between the electrons' kinetic and electrostatic energies. Recently, signatures of a TLL have been reported for the topological edge states of quantum spin Hall (QSH) insulators, strictly 1D electronic structures with linear (Dirac) dispersion and spin-momentum locking. Here we show that the many-body interactions in such helical Luttinger Liquid can be effectively controlled by the edge state's dielectric environment. This is reflected in a tunability of the Luttinger parameter K, distinct on different edges of the crystal, and extracted to high accuracy from the statistics of tunnelling spectra at tens of tunnelling points. The interplay of topology and many-body correlations in 1D helical systems has been suggested as a potential avenue towards realising non-Abelian parafermions. In one-dimensional systems, electronic interactions lead to a breakdown of Fermi liquid theory and the formation of a Tomonaga Luttinger Liquid (TLL), as recently reported in the helical edge states of quantum spin Hall insulators. Here, the authors show that the many-body interactions in the helical TLL of 1T'- WTe2 can be effectively controlled by the dielectric screening via the substrate. [ABSTRACT FROM AUTHOR]

Most topological insulators (TIs) discovered today in spinful systems can be transformed from topological semimetals (TSMs) with vanishing bulk gap via introducing the spin-orbit coupling (SOC), which manifests the intrinsic links between the gapped topological insulator phases and the gapless TSMs. Recently, we have discovered a family of TSMs in time-reversal invariant spinless systems, which host butterfly-like nodal-lines (NLs) consisting of a pair of identical concentric intersecting coplanar ellipses (CICE). In this Communication, we unveil the intrinsic link between this exotic class of nodal-line semimetals (NLSMs) and a Z 4 = 2 topological crystalline insulator (TCI), by including substantial SOC. We demonstrate that in three space groups (i.e., Pbam (No.55), P4/mbm (No.127), and P42/mbc (No.135)), the TCI supports a fourfold Dirac fermion on the (001) surface protected by two glide symmetries, which originates from the intertwined drumhead surface states of the CICE NLs. The higher order topology is further demonstrated by the emergence of one-dimensional helical hinge states, indicating the discovery of a higher order topological insulator protected by a glide symmetry. [ABSTRACT FROM AUTHOR]

The quantum behaviour of electrons in materials is the foundation of modern electronics and information technology1–11, and quantum materials with topological electronic and optical properties are essential for realizing quantized electronic responses that can be used for next generation technology. Here we report the first observation of topological quantum properties of chiral crystals6,7 in the RhSi family. We find that this material class hosts a quantum phase of matter that exhibits nearly ideal topological surface properties originating from the crystals' structural chirality. Electrons on the surface of these crystals show a highly unusual helicoid fermionic structure that spirals around two high-symmetry momenta, indicating electronic topological chirality. The existence of bulk multiply degenerate band fermions is guaranteed by the crystal symmetries; however, to determine the topological invariant or charge in these chiral crystals, it is essential to identify and study the helicoid topology of the arc states. The helicoid arcs that we observe on the surface characterize the topological charges of ±2, which arise from bulk higher-spin chiral fermions. These topological conductors exhibit giant Fermi arcs of maximum length (π), which are orders of magnitude larger than those found in known chiral Weyl fermion semimetals5,8–11. Our results demonstrate an electronic topological state of matter on structurally chiral crystals featuring helicoid-arc quantum states. Such exotic multifold chiral fermion semimetal states could be used to detect a quantized photogalvanic optical response, the chiral magnetic effect and other optoelectronic phenomena predicted for this class of materials6. Angle-resolved photoemission spectroscopy measurements reveal that CoSi and RhSi are nearly ideal topological conductors, with structural chirality and surface helicoid arcs of topological charge ±2 arising from bulk multifold chiral states. [ABSTRACT FROM AUTHOR]

The newly discovered topological crystalline insulators feature a complex band structure involving multiple Dirac cones, and are potentially highly tunable by external electric field, temperature or strain. Theoretically, it has been predicted that the various Dirac cones, which are offset in energy and momentum, might harbour vastly different orbital character. However, their orbital texture, which is of immense importance in determining a variety of a material's properties remains elusive. Here, we unveil the orbital texture of Pb1−xSnxSe, a prototypical topological crystalline insulator. By using Fourier-transform scanning tunnelling spectroscopy we measure the interference patterns produced by the scattering of surface-state electrons. We discover that the intensity and energy dependences of the Fourier transforms show distinct characteristics, which can be directly attributed to orbital effects. Our experiments reveal a complex band topology involving two Lifshitz transitions and establish the orbital nature of the Dirac bands, which could provide an alternative pathway towards future quantum applications. [ABSTRACT FROM AUTHOR]

Silicene is a one-atom-thick two-dimensional crystal of silicon with a hexagonal lattice structure that is related to that of graphene but with atomic bonds that are buckled rather than flat. This buckling confers advantages on silicene over graphene, because it should, in principle, generate both a band gap and polarized spin-states that can be controlled with a perpendicular electric field. Here we use first-principles calculations to show that field-gated silicene possesses two gapped Dirac cones exhibiting nearly 100% spin-polarization, situated at the corners of the Brillouin zone. Using this fact, we propose a design for a silicene-based spin-filter that should enable the spin-polarization of an output current to be switched electrically, without switching external magnetic fields. Our quantum transport calculations indicate that the proposed designs will be highly efficient (nearly 100% spin-polarization) and robust against weak disorder and edge imperfections. We also propose a Y-shaped spin/valley separator that produces spin-polarized current at two output terminals with opposite spins. [ABSTRACT FROM AUTHOR]

High mortality rates in patients with methamphetamine use disorder (MUD) are well documented. However, the influence of co-occurring psychiatric disorders on the risks of various causes of mortality, especially suicide, has not been elucidated. The objective of this study is to investigate the impacts of co-occurring psychiatric disorders on mortality in patients with MUD and their associations with age and gender. We used the Taiwan National Health Insurance Research Database to construct a population-based cohort of patients with MUD between January 1, 2002, and December 31, 2017. Mortality data were obtained by linking to the National Death Certification Database. All patients were followed up until their death or the end of the study (December 31, 2018), whichever occurred first. The main outcomes and measures are the outcomes were death and the underlying cause of death. In total, 21,809 patients with MUD were included. During a median follow-up time of 6 (interquartile range: 3 ~ 12) years, we recorded 2245 (10.29%) deaths. Patients with MUD were more likely to die from unnatural causes than natural causes, with respective mortality rates of 689 and 665 per 100,000 person-years. MUD patients with co-occurring psychiatric disorders had increased all-cause mortality (adjusted hazard ratio (aHR): 1.6, 95% confidence interval (CI) = 1.47 ~ 1.75), natural mortality (aHR: 1.37, 95% CI = 1.22 ~ 1.55), unnatural mortality (aHR: 1.93, 95% CI = 1.71 ~ 2.19), and suicides (aHR: 2.35, 95% CI = 1.96–2.82) than those without co-occurring disorders. Patients with co-occurring bipolar disorder had the highest risk of suicide, followed by those with depression, schizophrenia, and anxiety disorders. Furthermore, young women (< 25 years old) with MUD who had co-occurring psychotic disorders exhibited a 2.70-fold increase in suicide risk over those who had no co-occurring disorders. Co-occurring psychotic disorders are important factors in mortality and suicide of MUD patients. These results may enhance clinicians’ attention to provide proper treatment and timely interventions for individuals with co-existing MUD and mental disorders. [ABSTRACT FROM AUTHOR]