Publisher's Note: Anomalous Hall Effect in a 2D Rashba Ferromagnet [Phys. Rev. Lett. 117, 046601 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.117.046601.

Robust weak antilocalization due to spin-orbital entanglement in Dirac material Sr3SnO.

The presence of both inversion (P) and time-reversal (T) symmetries in solids leads to a double degeneracy of the electronic bands (Kramers degeneracy). By lifting the degeneracy, spin textures manifest themselves in momentum space, as in topological insulators or in strong Rashba materials. The existence of spin textures with Kramers degeneracy, however, is difficult to observe directly. Here, we use quantum interference measurements to provide evidence for the existence of hidden entanglement between spin and momentum in the antiperovskite-type Dirac material Sr3SnO. We find robust weak antilocalization (WAL) independent of the position of EF. The observed WAL is fitted using a single interference channel at low doping, which implies that the different Dirac valleys are mixed by disorder. Notably, this mixing does not suppress WAL, suggesting contrasting interference physics compared to graphene. We identify scattering among axially spin-momentum locked states as a key process that leads to a spin-orbital entanglement.

Localization Effects on Magnetotransport of a Disordered Weyl Semimetal.

We study longitudinal magnetotransport in a disordered Weyl semimetal taking into account localization effects in the vicinity of a Weyl node exactly. In a magnetic field, a single chiral Landau level coexists with a number of conventional nonchiral levels. Disorder scattering mixes these topologically different modes leading to very strong localization effects. We derive the average conductance as well as the full distribution function of transmission probabilities along the field direction. Remarkably, we find that localization of the nonchiral modes is greatly enhanced in a strong magnetic field with the typical localization length scaling as 1/B. Technically, we use the nonlinear sigma-model formalism with a topological term describing the chiral states. The problem is solved exactly by mapping to an equivalent transfer matrix Hamiltonian.

Anomalous Hall Effect in a 2D Rashba Ferromagnet.

Skew scattering on rare impurity configurations is shown to dominate the anomalous Hall effect in a 2D Rashba ferromagnet. The mechanism originates in scattering on rare impurity pairs separated by distances of the order of the Fermi wavelength. The corresponding theoretical description goes beyond the conventional noncrossing approximation. The mechanism provides the only contribution to the anomalous Hall conductivity in the most relevant metallic regime and strongly modifies previously obtained results for lower energies in the leading order with respect to impurity strength.

Lévy Flights due to Anisotropic Disorder in Graphene.

We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent T-matrix approximation.

Density of states in a two-dimensional chiral metal with vacancies.

We study quantum interference effects in a two-dimensional chiral metal (bipartite lattice) with vacancies. We demonstrate that randomly distributed vacancies constitute a peculiar type of chiral disorder leading to strong modifications of critical properties at zero energy as compared to those of conventional chiral metals. In particular, the average density of states diverges as ρ∝E(-1)|lnE|(-3/2) and the correlation length L(c)∝√[|lnE|] in the limit E→0. When the average density of vacancies is different in the two sublattices, a finite concentration of zero modes emerges and a gap in the quasiclassical density of states opens around zero energy. Interference effects smear this gap, resulting in exponentially small tails at low energies.

Quantum Hall criticality and localization in graphene with short-range impurities at the Dirac point.

We explore the longitudinal conductivity of graphene at the Dirac point in a strong magnetic field with two types of short-range scatterers: adatoms that mix the valleys and "scalar" impurities that do not mix them. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample as a function of impurity coordinates; an averaging over impurity positions is then performed numerically. The conductivity σ is equal to the ballistic value 4e2/πh for each disorder realization, provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point with σ≃4×0.4e2/h at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms, the localization behavior is also obtained at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes: remarkably, all key manifestations of Anderson localization and criticality in two dimensions are observed numerically in a single setup.

Giant magnetodrag in graphene at charge neutrality.

We report experimental data and theoretical analysis of Coulomb drag between two closely positioned graphene monolayers in a weak magnetic field. Close enough to the neutrality point, the coexistence of electrons and holes in each layer leads to a dramatic increase of the drag resistivity. Away from charge neutrality, we observe nonzero Hall drag. The observed phenomena are explained by decoupling of electric and quasiparticle currents which are orthogonal at charge neutrality. The sign of magnetodrag depends on the energy relaxation rate and geometry of the sample.

Coulomb drag in graphene near the Dirac point.

We study Coulomb drag in graphene near the Dirac point, focusing on the regime of interaction-dominated transport. We establish a novel, graphene-specific mechanism of Coulomb drag based on fast interlayer thermalization, inaccessible by standard perturbative approaches. Using the quantum kinetic equation framework, we derive a hydrodynamic description of transport in double-layer graphene in terms of electric and energy currents. In the clean limit the drag becomes temperature independent. In the presence of disorder the drag coefficient at the Dirac point remains nonzero due to higher-order scattering processes and interlayer disorder correlations. At low temperatures (diffusive regime) these contributions manifest themselves in the peak in the drag coefficient centered at the neutrality point with a magnitude that grows with lowering temperature.

Color-dependent conductance of graphene with adatoms.

We study ballistic transport properties of graphene with a low concentration of vacancies or adatoms. The conductance of graphene doped to the Dirac point is found to depend on the relative distribution of impurities among different sites of the honeycomb lattice labeled in general by six colors. The conductivity is shown to be sensitive to the crystal orientation if adatom sites have a preferred color. Our theory is confirmed by numerical simulations using recursive Green's functions with no adjustable parameters.

Interaction-induced criticality in Z(2) topological insulators.

We study interaction effects in topological insulators with strong spin-orbit coupling. We find that the interplay of nontrivial topology and Coulomb repulsion induces a novel critical state on the surface of a three-dimensional topological insulator. Remarkably, this interaction-induced criticality, characterized by a universal value of conductivity, emerges without any adjustable parameters. Further, we predict a direct quantum-spin-Hall transition in two dimensions that occurs via a similar critical state.

Charge transport in graphene with resonant scatterers.

The full counting statistics for the charge transport through an undoped graphene sheet in the presence of strong potential impurities is studied. Treating the scattering off the impurity in the s-wave approximation, we calculate the impurity correction to the cumulant generating function. This correction is universal provided the impurity strength is tuned to a resonant value. In particular, the conductance of the sample acquires a correction of 16e{2}/(pi{2}h) per resonant impurity.

Diffusion and criticality in undoped graphene with resonant scatterers.

A general theory is developed to describe graphene with an arbitrary number of isolated impurities. The theory provides a basis for an efficient numerical analysis of the charge transport and is applied to calculate the Dirac-point conductivity σ of graphene with resonant scatterers. In the case of smooth resonant impurities the symmetry class is identified as DIII and σ grows logarithmically with increasing impurity concentration. For vacancies (or strong on-site potential impurities, class BDI) σ saturates at a constant value that depends on the vacancy distribution among two sublattices.

Quantum criticality and minimal conductivity in graphene with long-range disorder.

We consider the conductivity sigma of graphene with negligible intervalley scattering at half filling. We derive the effective field theory, which, for the case of a potential disorder, is a symplectic-class sigma model including a topological term with theta=pi. As a consequence, the system is at a quantum critical point with a universal value of the conductivity of the order of e(2)/h. When the effective time-reversal symmetry is broken, the symmetry class becomes unitary, and sigma acquires the value characteristic for the quantum Hall transition.

Coulomb blockade of proximity effect at large conductance.

We consider the proximity effect in a normal dot coupled to a bulk superconducting reservoir by the tunnel contact with large normal conductance. Coulomb interaction in the dot suppresses the proximity minigap induced in the normal part of the system. We find exact expressions for the thermodynamic and tunneling minigaps as functions of the junction's capacitance. The tunneling minigap interpolates between its proximity-induced value in the regime of weak Coulomb interaction to the Coulomb gap in the regime of strong interaction. In the intermediate case a nonuniversal two-step structure of the tunneling density of states is predicted. The charge quantization in the dot is also studied.

LipC, a second lipase of Pseudomonas aeruginosa, is LipB and Xcp dependent and is transcriptionally regulated by pilus biogenesis components.

We have isolated cosmids that complement a Pseudomonas aeruginosa export-impaired mutant by increasing growth on lipid agar, a medium that requires lipase expression and export. These cosmids encode a previously unidentified lipase, LipC, which has high homology to the P. aeruginosa lipA gene product. Like LipA, LipC activity requires the chaperone activity of the lipB gene product and a functional xcp gene cluster for export. However, expression of LipC is barely detectable in a wild-type background. Transposon insertions that increase lipC promoter activity have been obtained that inactivate two pilus biogenesis genes, pilX and pilY1. This suggests that these proteins either directly or indirectly repress the expression of LipC and may be involved in transducing an extracellular signal that regulates this lipase.

Identification of an additional member of the secretin superfamily of proteins in Pseudomonas aeruginosa that is able to function in type II protein secretion.

Pseudomonas aeruginosa is a prolific exporter of virulence factors and contains three of the four protein secretion systems that have been described in gram-negative bacteria. The P. aeruginosa type II general secretory pathway (GSP) is used to export the largest number of proteins from this organism, including lipase, phospholipase C, alkaline phosphatase, exotoxin A, elastase and LasA. Although these exoproteins contain no sequence similarity, they are specifically and efficiently transported by the secretion apparatus. Bacterial homologues of XcpQ (GspD), the only outer membrane component of this system, have been proposed to play the role of gatekeeper, by presumably interacting and recognizing the exported substrates to allow their passage through the outer membrane. While determining the phenotype of nonpolar deletions in each of the xcp genes, we have shown that a deletion of the P. aeruginosa strain K xcpQ does not completely abolish protein secretion. As the proposed function of XcpQ should be requisite for secretion, we searched for additional factors that could carry out this role. A cosmid DNA library from a PAK strain deleted for xcpP-Z was tested for its ability to increase protein secretion by screening for enhanced growth on lipid agar, a medium that selects for the secretion of lipase. In this manner, we have identified an XcpQ homologue, XqhA, that is solely responsible for the residual export observed in a deltaxcpQ strain, although it is not required for efficient secretion in wild-type P. aeruginosa. We have also demonstrated that this protein is capable of recognizing all of the exoproteins of P. aeruginosa, arguing against the proposed role of members of the secretin family as determinants of specificity.

Significance of sporadic deceleration during antepartum testing in term pregnancies.

We have investigated the significance of single sporadic deceleration during reactive nonstress testing in normal pregnancies at term. A prospective study was performed during a 1-year period including 4742 nonstress tests performed between the 38th and 42nd weeks of pregnancy in patients referred to our department for antepartum testing and without any complication or pathology. Nonstress test (NST) was carried out with the patient lying on her left side, and was defined as reactive if at least two accelerations of 15 beats/min (bpm) or more lasting 15 sec were observed in a 20-min period. Sporadic deceleration was defined as a decrease in the fetal heart rate to less than 90 bpm or a decrease of 40 bpm below the baseline, lasting at least 2 min. The sporadic deceleration was considered as single when only one appeared in the first 20 min of monitoring and repeated when observed again once in at least one subsequent monitoring. Thirty-four cases of single sporadic deceleration were observed among women with reactive NST. In 14 cases there were repeated sporadic decelerations. The patients were divided into two groups according to the presence or absence of repeated decelerations. Outcomes of patients with repeated sporadic decelerations were compared with a group of 34 patients where sporadic decelerations were not observed during the antepartum testing. A significantly higher percentage of pathological fetal heart rate traces during labor were observed in the group of repeated decelerations. In conclusion the presence of repeated sporadic decelerations during a reactive NST suggests that the cause of cord compromise is persistent and recurrent cord compression is possible. Therefore, in these cases an increased fetal risk could be expected.

Regulation of gene expression by repressor localization: biochemical evidence that membrane and DNA binding by the PutA protein are mutually exclusive.

The PutA protein from Salmonella typhimurium is a bifunctional enzyme that catalyzes the oxidation of proline to glutamate, a reaction that is coupled to the transfer of electrons to the electron transport chain in the cytoplasmic membrane. The PutA protein is also a transcriptional repressor that regulates the expression of the put operon in response to the availability of proline. Despite extensive genetic and biochemical studies of the PutA protein, it was not known if the PutA protein carries out both of these two opposing functions while membrane associated or if instead it carries them out in different cellular compartments. To distinguish between these alternatives, we directly assayed the binding of purified PutA protein to DNA and membranes in vitro. The results indicate that wild-type PutA does not simultaneously associate with DNA and membranes. In addition, PutA superrepressor mutants that exhibit increased repression of the put genes show a direct correlation between decreased membrane binding and increased DNA binding. These results support a model in which the PutA protein shuttles between the membrane (where it acts as an enzyme but lacks access to DNA-binding sites) and the cytoplasm (where it binds DNA and acts as a transcriptional repressor), depending on the availability of proline.

Protein phosphorylation on serine, threonine, and tyrosine residues modulates membrane-protein interactions and transcriptional regulation in Salmonella typhimurium.

There exists a plethora of tyrosine kinases that play essential roles in regulation of eukaryotic proteins. Several dual specificity kinases that phosphorylate proteins on threonine, serine, and tyrosine residues also play critical roles in eukaryotic phosphorylation cascades. In contrast, very few prokaryotic proteins have been shown to be phosphorylated on tyrosine residues, and the functions of the rare examples remain obscure. Furthermore, no dual specificity kinases have been described in prokaryotes. Our results indicate that PutA protein from the bacterium Salmonella typhimurium autophosphorylates on several threonine, serine, and tyrosine residues. PutA protein both represses the proline utilization (put) operon and degrades proline to glutamate. These two opposing functions are regulated by the availability of proline and the membrane sites needed for the proline dehydrogenase activity of PutA protein. In addition, these functions are modulated by phosphorylation of PutA protein. The rate of dephosphorylation of PutA protein is determined by the availability of proline and membranes. Dephosphorylated PutA protein has a higher DNA binding affinity than the phosphorylated protein and thus may prevent toxic overexpression of PutA protein in the absence of available membrane sites.