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The current work discusses on the effect of sodium (Na) and bismuth (Bi) ion doping at different concentrations in the compositional formula La0.67Sr0.33–yNay/2Biy/2MnO3 (y = 0, 0.0825, 0.165, 0.2475, 0.33) on structural, magnetic, magnetotransport and thermoelectric studies. X-ray diffraction confirms the R c space group with rhombohedral structure and the field emission scanning electron microscope images confirms a systematic growth of grains with increasing in NaBi concentrations. An enhancement in the ferromagnetic ordering and magnetic transitions above 325 K were observed up to y = 0.165 and they decrease thereafter. A broad maximum along with a double peak behavior were noticed in the temperature dependent resistivity curves and they disappear upon the application of external magnetic fields. The Seebeck coefficient show a change of sign from positive to negative with increasing temperature for lower concentrations of NaBi and they exhibit a negative sign for higher substitutions suggesting the variation in the nature of charge carriers. The small polaron hopping mechanism governs the resistivity and thermopower behavior in the high temperature regions while, electron-electron, electron-magnon, magnon-magnon scattering mechanism contributes in the low temperature region. [ABSTRACT FROM AUTHOR]

This study considers fundamental research in the field of nanomechanics of corrugated semiconductor nanomembranes from strained heterostructures. The results of the study of the magnetotransport of two-dimensional electron gas in a corrugated nanomembrane made of the GaAs/InGaAs heterofilm are presented. [ABSTRACT FROM AUTHOR]

The band inversion of topological materials in three spatial dimensions is intimately connected to the parity anomaly of 2D massless Dirac fermions, known from quantum field theory. At finite magnetic fields, the parity anomaly reveals itself as a non‐zero spectral asymmetry, i.e., an imbalance between the number of conduction and valence band Landau levels, due to the unpaired zero Landau level. This work reports the realization of this 2D Dirac physics at a single surface of the 3D topological insulator (Hg,Mn)Te. An unconventional re‐entrant sequence of quantized Hall plateaus in the measured Hall resistance can be directly related to the occurrence of spectral asymmetry in a single topological surface state. The effect should be observable in any topological insulator where the transport is dominated by a single Dirac surface state. [ABSTRACT FROM AUTHOR]

Harnessing electron spin within limited dimensions under applied magnetic fields can lead to spin‐assisted tunable light‐matter interactions, which form a crucial step in developing frequency‐agile opto‐spintronic structures toward next generation photonic devices. For this purpose, spin‐dependent magneto transport phenomena derived from ferromagnetic (FM)/nonmagnetic (NM) multilayer structures have recently emerged as a useful tool for dynamically tailoring electromagnetic waves. With this pretext, five layers of aluminum (Al)/nickel (Ni) based multilayer thin films in sub skin depth regime are studied in terahertz domain under low‐intensity (0 to 30 mT) magnetic fields while systematically varying the NM spacer layer (sandwiched between the FM layers) from 8 to 18 nm. Such thin multi‐layer films demonstrate conductivity variations up to ≈40% for 30 mT of applied field. Utilizing the same multilayer configurations, magnetic field induced tunability in a metasurface design is investigated that simultaneously manifests toroidal, dipolar, and other higher‐order modes. Further, multipolar analysis reveals that the nonradiative toroidal and radiative dipole modes can be enhanced by almost 56% and 183%, respectively, under 0–30 mT magnetic fields. Such magnetic field‐induced simultaneous control over radiative and non‐radiative resonances can be pivotal for next generation terahertz magnetophotonic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] Interfacing graphene with other low-dimensional material has gained attentions recently due to its potential to stimulate new physics and device innovations for optoelectronic and electronic applications. Here, we exploit a solution-processed approach to introduce colloidal quantum dot (CQD) to the bilayer graphene device. The magnetotransport properties of the graphene device is drastically altered due to the presence of the CQD potential, leading to the observation of AB-like oscillation in the quantum Hall regime and screening of the intervalley scattering. The anomalous magnetotransport behavior is attributed to the coulombic scattering introduced by the CQDs and is shown to be highly asymmetric depending on the polarity of the transport carriers. These results prove the potential of such flexible method for engineering microscopic scattering process and performance of the graphene device that may lead to intriguing device application in such hybrid system. [ABSTRACT FROM AUTHOR]

Trisodium bismuthide (Na3 Bi) is the first experimentally verified topological Dirac semimetal, and is a 3D analogue of graphene hosting relativistic Dirac fermions. Its unconventional momentum-energy relationship is interesting from a fundamental perspective, yielding exciting physical properties such as chiral charge carriers, the chiral anomaly, and weak anti-localization. It also shows promise for realizing topological electronic devices such as topological transistors. Herein, an overview of the substantial progress achieved in the last few years on Na3 Bi is presented, with a focus on technologically relevant large-area thin films synthesized via molecular beam epitaxy. Key theoretical aspects underpinning the unique electronic properties of Na3 Bi are introduced. Next, the growth process on different substrates is reviewed. Spectroscopic and microscopic features are illustrated, and an analysis of semiclassical and quantum transport phenomena in different doping regimes is provided. The emergent properties arising from confinement in two dimensions, including thickness-dependent and electric-field-driven topological phase transitions, are addressed, with an outlook toward current challenges and expected future progress.

Trisodium bismuthide (Na3 Bi) is the first experimentally verified topological Dirac semimetal, and is a 3D analogue of graphene hosting relativistic Dirac fermions. Its unconventional momentum-energy relationship is interesting from a fundamental perspective, yielding exciting physical properties such as chiral charge carriers, the chiral anomaly, and weak anti-localization. It also shows promise for realizing topological electronic devices such as topological transistors. Herein, an overview of the substantial progress achieved in the last few years on Na3 Bi is presented, with a focus on technologically relevant large-area thin films synthesized via molecular beam epitaxy. Key theoretical aspects underpinning the unique electronic properties of Na3 Bi are introduced. Next, the growth process on different substrates is reviewed. Spectroscopic and microscopic features are illustrated, and an analysis of semiclassical and quantum transport phenomena in different doping regimes is provided. The emergent properties arising from confinement in two dimensions, including thickness-dependent and electric-field-driven topological phase transitions, are addressed, with an outlook toward current challenges and expected future progress.

We report the observation of angular-dependent antisymmetric magnetoresistance (MR) in artificially deformed Co-Tb Hall bar structures with perpendicular magnetization. Simultaneous transport measurements and domain imaging show that the antisymmetric MR results from the generation of a single domain wall (DW) inclination due to the restricted geometry and is further proportional to the inclination-associated geometry factor. The results are well described by a theoretical model that is supported by analytic and numerical calculations of the nonequilibrium current and Hall voltage distribution in the vicinity of the inclined DW. This finding provides a straightforward and effective approach to control DW geometries, leading to various DW-based spintronic device applications. [ABSTRACT FROM AUTHOR]

A comprehensive study of superconducting properties of underdoped NaFe 0.979 Co 0.021 As single crystals by a combination of upper critical field measurements and incoherent multiple Andreev reflection effect (IMARE) spectroscopy is presented. The H c 2 (T) temperature dependences are measured at magnetic fields up to 16 T with in-plane and out-of-plane field directions and considered within single-band and two-band models in order to estimate the H c 2 (0) value. In IMARE spectroscopy probes, the magnitude, characteristic ratio, and temperature dependence of the superconducting order parameters ( Δ L , S (T) ) are determined locally and directly. A possible k-space anisotropy of the large superconducting gap is demonstrated. We show that usage of a quadruple of λ i j 0 coupling constants obtained in the IMARE experiment can significantly reduce the number of free parameters required to fit the H c 2 (T) dependence within a two-band approach (from six to two). [ABSTRACT FROM AUTHOR]

Unexpected, yet useful functionalities emerge when two or more materials merge coherently. Artificial oxide superlattices realize atomic and crystal structures that are not available in nature, thus providing controllable correlated quantum phenomena. This review focuses on 4d and 5d perovskite oxide superlattices, in which the spin–orbit coupling plays a significant role compared with conventional 3d oxide superlattices. Modulations in crystal structures with octahedral distortion, phonon engineering, electronic structures, spin orderings, and dimensionality control are discussed for 4d oxide superlattices. Atomic and magnetic structures, Jeff = 1/2 pseudospin and charge fluctuations, and the integration of topology and correlation are discussed for 5d oxide superlattices. This review provides insights into how correlated quantum phenomena arise from the deliberate design of superlattice structures that give birth to novel functionalities. [ABSTRACT FROM AUTHOR]

Anisotropic hopping in a toy Hofstadter model was recently invoked to explain a rich and surprising Landau spectrum measured in twisted bilayer graphene away from the magic angle. Suspecting that such anisotropy could arise from unintended uniaxial strain, we extend the Bistritzer-MacDonald model to include uniaxial heterostrain and present a detailed analysis of its impact on band structure and magnetotransport. We find that such strain strongly influences band structure, shifting the three otherwise-degenerate van Hove points to different energies. Coupled to a Boltzmann magnetotransport calculation, this reproduces previously unexplained nonsaturating B2 magnetoresistance over broad ranges of density near filling v = ±2 and predicts subtler features that had not been noticed in the experimental data. In contrast to these distinctive signatures in longitudinal resistivity, the Hall coefficient is barely influenced by strain, to the extent that it still shows a single sign change on each side of the charge neutrality point--surprisingly, this sign change no longer occurs at a van Hove point. The theory also predicts a marked rotation of the electrical transport principal axes as a function of filling even for fixed strain and for rigid bands. More careful examination of interaction-induced nematic order versus strain effects in twisted bilayer graphene could thus be in order. [ABSTRACT FROM AUTHOR]

The superconductivity and nontrivial topological electronic state are key hallmarks of topological superconductors. Here, we focus on the transport signals of possible topological surface state in the topological superconductor candidate β-PdBi2 nanoflake with a thickness of 21 nm. The resistance demonstrates a semiconductor-metal transition followed by an upturned behavior as the temperature decreases. A large and unsaturated longitudinal magnetoresistance (MR), accompanied by distinct Shubnikov-de Hass oscillation in Hall resistance, is observed. An analysis of Hall resistance reveals that the carriers present the characteristics of relativistic particles with small effective mass and extremely high mobility. The angle-dependent quantum oscillations demonstrate a two-dimensional Fermi surface topology. A giant anisotropic MR as large as 98% is detected when rotating the magnetic field. These results provide the possible transport signals of a nontrivial topological electronic state, establishing a further understanding of the topological properties of the low-dimensional topological superconductor candidate α-PdBi2. [ABSTRACT FROM AUTHOR]

Magnetotransport, the magnetic field induced electron transport phenomenon through metals and semiconductors, has proven to be a useful technique to tailor the properties of electromagnetic radiation upon interaction with suitable materials and structures. Very recently, magnetotransport has become an important tool to dynamically tailor terahertz (THz) radiation and response of different optical devices. Based on these backgrounds, optically thin, subwavelength superlattice (with alternate arrangement of four metallic films: two non‐magnetic aluminum [Al] and two ferromagnetic nickel [Ni] films, having thickness of each film as 10 nm) metasurfaces are demonstrated, consisting of periodic arrays of asymmetric cut‐wire pair metasurfaces, which have a unique ability to exhibit both frequency and intensity modulation at its hybridized resonances when low‐intensity magnetic fields are applied. Such dynamic tuning characteristics are attributed to the combined effects of spin‐dependent THz magnetotransport in superlattice films, near‐field electromagnetic coupling between the resonators, and lattice mode coupling. Such THz metasurface is further employed for non‐contact detection of external magnetic fields in the range of 0–30 mT, while operating at the optically thin regime. The demonstrated scheme can further be extended to realize THz magneto‐spectroscopy toward devising state‐of‐the‐art photonic and magnetic technologies. [ABSTRACT FROM AUTHOR]

Thin films of iron–tin alloy FeSn are grown on silicon substrates and their structural and transport properties are investigated for the first time. Herein, the molecular beam epitaxy method is used to grow 50 and 30 nm thick FeSn films on silicon substrates containing 10 nm of MgO as a buffer layer. The films are characterized structurally using an X‐ray diffractometer, showing a hexagonal crystal structure with the space group P6/mmm (191). The results from electrical and magnetotransport measurements show these films exhibit characteristics close to metals. Herein, the magnetotransport properties of the thin films which show positive magnetoresistance and sample‐dependent Hall effect with possible multiband transport are further measured. [ABSTRACT FROM AUTHOR]

In this paper, we have studied the electrical and magnetotransport properties of strontium-deficient Pr0.7Sr0.3 − xMnO3 polycrystalline manganites prepared by solid-state reaction. The temperature dependence of resistivity shows the presence of a metal–insulator transition at Tρ with the presence of resistivity minimum at very low temperatures. The Tρ values shift from 265 K for x = 0 to 157 K for x = 0.1 with increasing strontium deficiency. We have identified the transport mechanisms responsible for magnetotransport properties. Some peculiarities were obtained for x = 0.1 sample, which can be linked to the half-doped nature of this specimen. Colossal values of magnetoresistance (MR) were recorded for all our samples near Tρ (for µ0H = 2 T, negative MR values are 58%, 89% and 88% for x = 0, x = 0.05 and x = 0.1, respectively). –MR increases with increasing strontium deficiency. Colossal MR values suggests the possibility of using our samples for technological applications like magnetic field sensing and spintronics. [ABSTRACT FROM AUTHOR]

In this first volume, we cover relevant aspects of chemical and physical processes of the production and characterization of magnetic materials in bulk, thin films, nanostructures, and/or nanocomposites, as well as modeling aspects involving such structures. Accordingly, this volume presents eleven original research and review works on the challenges and trends covering fundamental and experimental work, with a special focus on the design, synthesis, and characterization of various types of magnetic materials, and the study of their structure–property relationships. State-of-the-art results on the development of new experimental concepts, leading to the transfer, chemical transformation, and high-resolution patterning of advanced thin films and nanomaterials, and to the design and fabrication of devices, are also presented and discussed. [ABSTRACT FROM AUTHOR]

The carbon nanowalls (CNWs) grown by Plasma-Enhanced CVD reveal differences in the magnetotransport properties depending on the synthesis parameters. In this paper, we report the influence of the deposition temperature, which produces variations of the disorder microstructure of the CNWs. Relative low disorder leads to the weak localization with the transition to weak antilocalization. Higher disorder generates positive Hopping mechanism in low field with a crossover to a diffusion transport by graphene nanocrystallites. The samples reveal a similitude of the isoline density of the MR at a low temperature (<50 K), explained in the context of the magnetization. This effect is independent of the number of defects. We can achieve a desirable amount of control over the MT properties changing the CNWs' microstructure. [ABSTRACT FROM AUTHOR]

We present a symmetrization routine that optimizes and eases the analysis of imperfect, experimental data featuring the anomalous Hall hysteresis. This technique can be transferred to any hysteresis with (point-)symmetric behavior. The implementation of the method is demonstrated exemplarily using intermixed longitudinal and transversal data obtained from a chromium-doped ternary topological insulator revealing a clear hysteresis. Furthermore, by introducing a mathematical description of the anomalous Hall hysteresis based on the error function precise values of the height and coercive field are determined.

It has been established that the Coulomb interactions can transform the electron gas into a viscous fluid. This fluid is realized in a number of platforms, including graphene and two-dimensional semiconductor heterostructures. The defining characteristic of the electron fluid is the formation of layers of charge carriers that are in local thermodynamic equilibrium, as in classical fluids. In the presence of nonuniformities, whirlpools and nontrivial flow profiles are formed, which have been directly imaged in recent experiments. In this paper, we theoretically study the response of the electron fluid to localized magnetic fields. We find that the electric current is suppressed by viscous vortices in regions where magnetic field is sharply varying, causing strong transport signatures. Experimentally, our considerations are relevant since local magnetic fields can be applied to the system through implanting adatoms or embedding micromagnets in the top-gate. Our theory is essential for the characterization and future applications of electron fluids in hydrodynamic spin transport. [ABSTRACT FROM AUTHOR]

Careful selection of the physical model of the material for a specific doping and selected operating temperatures is a non-trivial task. In numerical simulations that optimize practical devices such as detectors or lasers architecture, this challenge can be very difficult. However, even for such a well-known material as a 5 µm thick layer of indium arsenide on a semiinsulating gallium arsenide substrate, choosing a realistic set of band structure parameters for valence bands is remarkable. Here, the authors test the applicability range of various models of the valence band geometry, using a series of InAs samples with varying levels of p-type doping. Carefully prepared and pretested the van der Pauw geometry samples have been used for magneto-transport data acquisition in the 20-300 K temperature range and magnetic fields up to ±15 T, combined with a mobility spectra analysis. It was shown that in a degenerate statistic regime, temperature trends of mobility for heavy- and light-holes are uncorrelated. It has also been shown that parameters of the valence band effective masses with warping effect inclusion should be used for selected acceptor dopant levels and range of temperatures. [ABSTRACT FROM AUTHOR]

We report the ground state stabilization and corresponding electrical transport and magnetotransport properties of a 2D metallic system with an isotropic Fermi surface reconstructed by a charge density wave. The onset of the charge density wave is a spontaneous process, stabilized by the condensation energy gain due to the self-consistent mechanism of topological reconstruction of the Fermi surface and opening of the pseudo-gap around it. We address the signature of the uni-axial reconstruction in terms of the measurable quantities, such as the intra-band transport properties, including the one-particle density of states, the total and effective concentration of electrons, and the Hall coefficient. Additionally, we analyze the magnetotransport properties of the system reconstructed by the bi-axial, checkerboard-like charge density wave, under conditions of magnetic breakdown. It manifests huge quantum oscillations in diagonal components of magnetoconductivity, while the Hall conductivity changes sign, varying the external magnetic field with a finite region of vanishing Hall coefficient in between. [ABSTRACT FROM AUTHOR]

Our studies formulate a classical theory to study the influence of in-plane electric field on electron-impurity scattering process and magnetotransport in a two-dimensional space, in the presence of a strong out-of-plane magnetic field. Our studies connect classical scattering and quantum Landau Level broadening, as will be reviewed in this report. We derived an electric current formula in agreement with the current derived from the Drude theory under a strong magnetic field. Our electric current formula is derived microscopically from the migration of the guiding centres at strong magnetic field regime ω τ > 1. The electron-impurity scattering under electromagnetic field not only shifts the guiding centre coordinates X and Y, but also changes cyclotron radius R. The change of cyclotron radius R compensates the change of the electric potential energy during the scattering process. The broadening of cyclotron radius is a classical manifestation of Landau Levels broadening. Our conductivity m n B 2 τ derived from our current formula in the linear response regime results in the same as the current derived from Kubo current fluctuation theory, providing a special case of the fluctuation-dissipation theorem. [ABSTRACT FROM AUTHOR]

β-Mn-type chiral cubic CoxZnyMnz (x + y + z = 20) alloys present a intriguing platform for&#xD;exploring topological magnetic orderings with promising spintronic potential. This study examines the magnetotransport properties of Co6.5Ru1.5Zn8Mn4, a skyrmion-hosting β-Mn-type chiral compound. The longitudinal resistivity (ρxx) exhibits field-insensitive low-temperature minima due to quantum interference effects, driven by T1/2-dependent electron-electron interactions. We observe a substantial intrinsic anomalous Hall conductivity (AHC), unaffected by quantum interference. Additionally, a pronounced topological Hall effect is observed at the metastable skyrmionic state, persisting up to TC and achieving notable magnitudes for stoichiometric compounds. These results position the CoxZnyMnz family favourably to leverage the rich palette of emergent magnetotransport properties for spintronic applications., (© 2025 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

We present a straightforward method which may greatly simplify and lower the threshold for determining the phase of the relatively enigmatic quantum material-ZrTe 5 . In this study, without directly probing the band structure, we identify the topological phase of the three-dimensional (3D) bulk ZrTe 5 crystal solely through low-temperature electrical and magnetotransport measurements. A two-dimensional (2D) weak antilocalization (WAL) effect was observed in our bulk ZrTe 5 crystal, along with clear Shubnikov-de Haas oscillations. The large prefactorαderived from WAL analyses indicates the presence of multiple conducting channels in the bulk ZrTe 5 crystal, where each channel is associated with individual 2D ZrTe 5 layers. It is the largeαvalue provides insights into the topological Dirac semimetal phase inherent to our ZrTe 5 crystal. Additionally, we analyze the pronounced linear magnetoresistance and saturation behavior under a perpendicular magnetic field. Our results suggest that bulk ZrTe 5 crystals, which exhibit unique layered transport features, serve as a promising platform for further research in quantum phases and transitions in 3D quantum systems., (Creative Commons Attribution license.)

Weyl fermions are one of the simplest objects that link ideas in geometry and topology to high-energy physics and condensed matter physics. Although the existence of Weyl fermions as elementary particles remains dubious, there is mounting evidence of their existence as quasiparticles in certain condensed matter systems. Such systems are termed Weyl semimetals (WSMs). Needless to say, WSMs have emerged as a fascinating class of materials with unique electronic properties, offering a rich playground for both fundamental research and potential technological applications. This review examines recent advancements in understanding electron transport in WSMs. We begin with a pedagogical introduction to the geometric and topological concepts critical to understanding quantum transport in Weyl fermions. We then explore chiral anomaly, a defining feature of WSMs, and its impact on transport phenomena such as longitudinal magnetoconductance and planar Hall effect. The Maxwell-Boltzmann transport theory extended beyond the standard relaxation-time approximation is then discussed in the context of Weyl fermions, which is used to evaluate various transport properties. Attention is also given to the effects of strain-induced gauge fields and external magnetic fields in both time-reversal broken and inversion asymmetric inhomogeneous WSMs. The review synthesizes theoretical insights, experimental observations, and numerical simulations to provide a comprehensive understanding of the complex transport behaviors in WSMs, aiming to bridge the gap between theoretical predictions and experimental verification., (© 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)

Intercalation is a promising technique to modify the structural and electronic properties of 2D materials on the wafer scale for future electronic device applications. Yet, few reports to date demonstrate 2D intercalation as a viable technique on this scale. Spurred by recent demonstrations of mm-scale sensors, we use hydrogen intercalated quasi-freestanding bilayer graphene (hQBG) grown on 6H-SiC(0001), to understand the electronic properties of a large-area (16 mm 2 ) device. To do this, we first analyze Shubnikov-de Haas (SdH) oscillations and weak localization, permitting determination of the Fermi level, cyclotron effective mass, and quantum scattering time. Our transport results indicate that at low temperature, scattering in hQBG is dominated by charged impurities and electron-electron interactions. Using low- temperature scanning tunneling microscopy and spectroscopy (STS), we investigate the source of the charged impurities on the nm-scale via observation of Friedel oscillations. Comparison to theory suggests that the Friedel oscillations we observe are caused by hydrogen vacancies underneath the hQBG. Furthermore, STS measurements demonstrate that hydrogen vacancies in the hQBG have an extremely localized effect on the local density of states, such that the Fermi level of the hQBG is only affected directly above the location of the defect. Hence, we find that the calculated Fermi level from SdH oscillations on the millimeter scale agrees with the value measured locally on the nanometer scale with STS measurements.

We set out to demonstrate the development of a highly conductive polymer based on poly-(3,4-ethylenedithia thiophene) (PEDTT), PEDOTs structural analogue historically notorious for structural disorder and limited conductivities. The caveat therein was previously described to lie in intra-molecular repulsions. We demonstrate how a tremendous >2600-fold improvement in conductivity and metallic features, such as magnetoconductivity can be achieved. This is achieved through a careful choice of the counter-ion (sulphate) and the use of oxidative chemical vapour deposition (oCVD). It is shown that high structural order on the molecular level was established and the formation of crystallites tens of nanometres in size was achieved. We infer that the sulphate ions therein intercalate between the polymer chains, thus forming densely packed crystals of planar molecules with extended π-systems. Consequently, room-temperature conductivities of above 1000 S cm−1 are achieved, challenging those of conventional PEDOT:PSS. The material is in the critical regime of the metal–insulator transition.

The paper covers some measurement aspects of transport of electrons through metals and semiconductors in magnetic field – magnetotransport – allowing for the determination of electrical parameters characteristic of three-dimensional (3D) topological insulators (TI) (i.e. those that behave like an insulator inside their volume and have a conductive layer on their surface). A characteristic feature of the 3D TI is also a lack of differences between the chemical composition of the conductive surface and the interior of the material tested and the fact that the electron states for its surface conductivity are topologically protected. In particular, the methods of generating strong magnetic fields, obtaining low temperatures, creating electrical contacts with appropriate geometry were presented, and the measurement methods were reviewed. In addition, the results of magnetotransport measurements obtained for two volumetric samples based on the HgCdTe compound grown with the molecular beam epitaxy method are presented.

The magnetotransport behavior inside the nematic phase of bulk FeSe reveals unusual multiband effects that cannot be reconciled with a simple two-band approximation proposed by surface-sensitive spectroscopic probes. In order to understand the role played by the multiband electronic structure and the degree of two-dimensionality, we have investigated the electronic properties of exfoliated flakes of FeSe by reducing their thickness. Based on magnetotransport and Hall resistivity measurements, we assess the mobility spectrum that suggests an unusual asymmetry between the mobilities of the electrons and holes, with the electron carriers becoming localized inside the nematic phase. Quantum oscillations in magnetic fields up to 38 T indicate the presence of a hole-like quasiparticle with a lighter effective mass and a quantum scattering time three times shorter, as compared with bulk FeSe. The observed localization of negative charge carriers by reducing dimensionality can be driven by orbitally dependent correlation effects, enhanced interband spin fluctuations, or a Lifshitz-like transition, which affect mainly the electron bands. The electronic localization leads to a fragile two-dimensional superconductivity in thin flakes of FeSe, in contrast to the two-dimensional high-Tc induced with electron doping via dosing or using a suitable interface. [ABSTRACT FROM AUTHOR]

While the pseudogap dominates the phase diagram of hole-doped cuprates, connecting the antiferromagnetic parent insulator at low doping to the strange metal at higher doping, its origin and relation to superconductivity remains unknown. In order to proceed, a complete understanding of how the single hole–initially localized in the Mott state–becomes mobile and ultimately evolves into a coherent quasiparticle at the end of the superconducting dome is required. In order to affect this development, we examine recent transport and spectroscopic studies of hole-doped cuprates across their phase diagram. In the process, we highlight a set of empirical correlations between the superfluid density and certain normal state properties of hole-doped cuprates that offer fresh insights into the emergence of metallicity within the CuO2 plane and its influence on the robustness of the superconducting state. We conclude by arguing that the overall behavior is best understood in terms of two distinct current-carrying fluids, only one of which dominates the superconducting condensate and is gapped out below the pseudogap endpoint at a critical hole concentration p∗.

The molecular scale magnetic proximity effect is proposed in single-molecule magnetic junctions (SMMJs) consisting of a dissociated amine-ended 1,4-benzenediamine (BDA) molecule coupled to two ferromagnetic Co electrodes. Our self-developed JunPy + Landau-Lifshitz-Gilbert simulation combined with first-principles calculation is employed to investigate the role of contact geometry in the magnetotransport properties of SMMJs with the choice of top, bridge, and hollow contact sites. The strong spinterface effect gives rise to distinct angular dependence of equilibrium field-like spin torque (FLST), asymmetric magnetic hysteresis loop and tunable exchange bias. From the analytical derivation of nonequilibrium Keldysh formalism, we believe that a promising way forward is to activate the multi-reflection process via the so-called molecular spinterface that will allow us to conquer as-yet unexplored magnetotransport properties of organic-based spintronics.

A series of magnetotransport experiments has been designed to investigate single-crystalline LaBi samples subjected to different degrees of air exposure. As the air exposure time increases, the temperature-dependent resistance changes from the typical behaviour of a good metal to that of a bad metal, exhibiting a negative temperature coefficient. Additionally, the magnetoresistance in the sample with the longest air exposure becomes linear in the magnetic field, instead of the ubiquitous quadratic magnetoresistance observed in many other related rare-earth monopnictides. Despite these drastic changes, the Shubnikov–de Haas oscillations remain almost unaffected by air exposure — the frequency spectra and the effective masses do not vary as the air exposure time increases. Our results suggest the existence of two separate contributions to the transport data: one from the surface and the other from the bulk. Given the topological nature of LaBi, our results suggest controlled air exposure provides an effective means to distinguish between surface and bulk states. [ABSTRACT FROM AUTHOR]

A strong disorder characterized by a small product of the Fermi vector kF and the electron mean free l drives superconductors towards insulating state. Such disorder can be introduced by making the films very thin. Here, we present 3-nm Mo2N film with kF*l ~ 2 with a resistive superconducting transition temperature Tc = 2 K heavily suppressed in comparison with the bulk Tc. Superconducting density of states (DOS) with smeared gap-like peaks and in-gap states, so called Dynes DOS, is observed by the low-temperature tunneling spectroscopy despite a sharp resistive transition. By scanning tunneling microscope, the spectral maps are obtained and related to the surface topography. The maps show a spatial variation of the superconducting energy gap on the order of 20% which is not accidental but well correlates with the surface corrugation: protrusions reveal larger gap, smaller spectral smearing, and smaller in-gap states. In agreement with our previous measurements on ultrathin MoC films, we suggest that the film-substrate interface introducing the local pair-breaking is responsible for the observed effects and generally for the suppression of the superconductivity in these ultrathin films. [ABSTRACT FROM AUTHOR]

Exploration of the phase transition is one of the hottest topics in condensed matter physics. In this paper, we have fabricated 2H-MoTe2 devices and investigated their magnetotransport properties. As temperature decreases, the 2H-MoTe2 flake undergoes several metalâ€"insulator transitions, including insulator-to-metal transitions at ∼143 K and ∼36 K, respectively, and metal-to-insulator transitions at ∼109 K. In addition, these transitions are not affected by the application of external magnetic fields. The possible physical mechanisms behind these intriguing transitions originate from the electronâ€"phonon coupling and the impurity scattering in the 2H-MoTe2 flakes. [ABSTRACT FROM AUTHOR]

Oxide heterostructures allow for detailed studies of 2D electronic transport phenomena. Herein, different facets of magnetotransport in selected spin–orbit‐coupled systems are analyzed and characterized by their single‐band and multiband behavior, respectively. Experimentally, temperature and magnetic field dependent measurements in the single‐band system BaPbO3/SrTiO3 reveal strong interplay of weak antilocalization (WAL) and electron–electron interaction (EEI). Within a scheme which treats both, WAL and EEI, on an equal footing a strong contribution of EEI at low temperatures is found which suggests the emergence of a strongly correlated ground state. Furthermore, now considering multiband effects as they appear, e.g., in the model system LaAlO3/SrTiO3, theoretical investigations predict a huge impact of filling on the topological Hall effect in systems with intermingled bands. Already weak band coupling produces striking deviations from the well‐known Hall conductivity that are explainable in a fully quantum mechanical treatment which builds upon the hybridization of intersecting Hofstadter bands. [ABSTRACT FROM AUTHOR]

The majority of proposed exotic applications employing 3D topological insulators require high-quality materials with reduced dimensions. Catalyst-free, PVD-grown Bi2Se3 nanoribbons are particularly promising for these applications due to the extraordinarily high mobility of their surface Dirac states, and low bulk carrier densities. However, these materials are prone to the formation of surface accumulation layers; therefore, the implementation of surface encapsulation layers and the choice of appropriate dielectrics for building gate-tunable devices are important. In this work, all-around ZnO-encapsulated nanoribbons are investigated. Gate-dependent magnetotransport measurements show improved charge transport characteristics as reduced nanoribbon/substrate interface carrier densities compared to the values obtained for the as-grown nanoribbons on SiO2 substrates. [ABSTRACT FROM AUTHOR]

A comprehensive magnetotransport study on a p‐type single crystal of SnTe topological crystalline insulator is reported, across the cubic‐to‐rhombohedral (R3m) transition at Ts ≈64 K. SnTe exhibits a large unsaturated linear magnetoresistance (LMR) reaching a value of 42% at 5 K and 8 T for (100) plane. LMR is found to have a direct dependence on the mobility and a detailed analysis shows that it follows the classical Parish‐Littlewood model of conductivity fluctuations arising from macroscopic inhomogeneities of tellurium interstitial atoms. Profound SdH oscillations having a π Berry phase are observed in the rhombohedral (R3m) phase having significantly lower carrier density ≈5.32 × 1011 cm−2 at 2 K, which provides direct evidence of protected topological surface states in the R3m phase. The Hall conductivity shows a transformation from one band to two‐band behavior across the structural transition, thus providing an experimental evidence for the degeneracy lifting of bulk valence bands below the cubic symmetry breaking point which is consistent with recent band structure calculations. The overall results indicate that magnetotransport studies can distinctly probe the surface and bulk sensitive properties of SnTe, and can also track the band‐splitting of degenerate bands across the cubic‐to‐rhombohedral (R3m) transition. [ABSTRACT FROM AUTHOR]