Valley-Polarized Quantum Hall Phase in a Strain-Controlled Dirac System.

In multivalley systems, the valley pseudospin offers rich physics going from encoding of information by its polarization (valleytronics), to exploring novel phases of matter when its degeneracy is changed. Here, by strain engineering, we reveal fully valley-polarized quantum Hall phases in the Pb_{1-x}Sn_{x}Se Dirac system. Remarkably, when the valley energy splitting exceeds the fundamental band gap, we observe a "bipolar quantum Hall phase," heralded by the coexistence of hole and electron chiral edge states at distinct valleys in the same quantum well. This suggests that spatially overlaid counterpropagating chiral edge states emerging at different valleys do not interfere with each other.

Persistent magnetic coherence in magnets.

When excited, the magnetization in a magnet precesses around the field in an anticlockwise manner on a timescale governed by viscous magnetization damping, after which any information carried by the initial actuation seems to be lost. This damping appears to be a fundamental bottleneck for the use of magnets in information processing. However, here we demonstrate the recall of the magnetization-precession phase after times that exceed the damping timescale by two orders of magnitude using dedicated two-colour microwave pump-probe experiments for a Y3Fe5O12 microstructured film. Time-resolved magnetization state tomography confirms the persistent magnetic coherence by revealing a double-exponential decay of magnetization correlation. We attribute persistent magnetic coherence to a feedback effect, that is, coherent coupling of the uniform precession with long-lived excitations at the minima of the spin-wave dispersion relation. Our finding liberates magnetic systems from the strong damping in nanostructures that has limited their use in coherent information storage and processing.

The development of internal pressure standards for in-house elastic wave velocity measurements in multi-anvil presses.

Ultrasonic systems are powerful tools to determine elastic wave velocities of minerals and materials at high pressure and temperature and have been extensively developed in recent decades. However, accurate measurement of sample length is required to convert travel times into wave velocities, limiting their use to synchrotron facilities or room temperature experiments in laboratories. We have made use of a close collaboration between the Bayerisches Geoinstiut and the P61B end-station beamline (PETRA III - DESY) to install ultrasonic systems and develop a novel dual travel time method for in situ pressure determination without the need for synchrotron radiation. Our method relies on the travel times of elastic waves through a reference material; it requires a thermocouple and is non-intrusive, with the reference material replacing the backing plate of the high-pressure assembly. Pressures obtained from this dual travel time method show excellent agreement with those obtained from x-ray diffraction using synchrotron radiation on standard materials. Our novel method enables in situ pressure determination at varying temperatures during in-house ultrasonic interferometry experiments. This allows us not only to determine the elastic behavior of minerals and materials but also to investigate phase diagrams, solidus, or liquidus conditions at varying pressures and temperatures during in-house experiments. During the installation of the pulse-echo ultrasonic system, we identified critical parameters for obtaining reliable data. While these requirements are well-known to experts, this study presents a comprehensive review of the different characteristics of ultrasonic systems, providing user-friendly guidelines for new users installing and operating such systems in high-pressure and high-temperature conditions.

Improved demodulated phase signal resolution for carrier signals with small modulation index by clipping and synchronous sampling for heterodyne interferometers.

Digitization of phase-modulated carrier signals with a commercially available analog-to-digital converter (ADC) is a common task in many communication and sensor applications. ADCs deliver phase-modulated digital carrier signals, which are numerically demodulated in order to extract the relevant information. However, the limited dynamic ranges of available ADCs limit the carrier-to-noise ratio of carrier signals after digitization. Correspondingly, the resolution of the demodulated digital signal is degraded. We demonstrate a sampling method with a simple demodulation scheme for phase-modulated signals with a small modulation index. Our new scheme overcomes the limitation due to digital noise defined by the ADC. Through simulations and experiments, we provide evidence that our method can improve the resolution of the demodulated digital signal significantly, when the carrier-to-noise ratio of phase-modulated signals is limited by digital noise. We employ our sampling and demodulation scheme to solve the problem of a possible degradation of measurement resolution after digital demodulation in heterodyne interferometers measuring small vibration amplitudes.

Giant magnon spin conductivity in ultrathin yttrium iron garnet films.

Conductivities are key material parameters that govern various types of transport (electronic charge, spin, heat and so on) driven by thermodynamic forces. Magnons, the elementary excitations of the magnetic order, flow under the gradient of a magnon chemical potential1-3 in proportion to a magnon (spin) conductivity. The magnetic insulator yttrium iron garnet is the material of choice for efficient magnon spin transport. Here we report a giant magnon conductivity in thin yttrium iron garnet films with thicknesses down to 3.7 nm when the number of occupied two-dimensional subbands is reduced from a large number to a few, which corresponds to a transition from three-dimensional to two-dimensional magnon transport. We extract a two-dimensional magnon spin conductivity around 1 S at room temperature, comparable to the (electronic) conductivity of the high-mobility two-dimensional electron gas in GaAs quantum wells at millikelvin temperatures4. Such high conductivities offer opportunities to develop low-dissipation magnon-based spintronic devices.

Order out of chaos: Sense of coherence and the mediating role of coping resources in explaining mental health during COVID-19 in 7 countries.

In the midst of the COVID-19 pandemic and the universal chaos created by it, this study explores the role of sense of coherence (Soc, Antonovsky, 1979) and how it enables coping with a stressful situation and staying well. SOC is a generalized orientation which allows one to perceive the world as comprehensible, manageable, and meaningful. In an attempt to understand 'how does the SOC work' we employed the salutogenic assumption that a strong SOC allows one to reach out in any given situation and find those resources appropriate to the specific stressor. Thus, we hypothesized that the positive impact of SOC on mental health outcomes would be mediated through coping resources that are particularly salient in times of crisis. One resource is related to the micro level (perceived family support) and the other concerns the macro level (trust in leaders and social-political institutions). Data collection was conducted in different countries during May-June 2020 via online platforms. The data included 7 samples of adult participants (age 18-90) from Israel (n â€‹= â€‹669), Italy (n â€‹= â€‹899), Spain (n â€‹= â€‹476), Germany (n â€‹= â€‹708), Austria (n â€‹= â€‹1026), Switzerland (n â€‹= â€‹147), and the U.S. (n â€‹= â€‹506). The questionnaires included standard tools (MHC-SF, SOC-13) as well as questionnaires of perceived family support and trust that were adapted to the pandemic context. As expected, SOC was associated with mental health in all the samples. Perceived family support and trust in leaders and social-political institutions mediated the relationships between SOC and mental health, controlling for age, gender, and level of financial risk. It appears that SOC has a universal meaning, not limited by cultural and situational characteristics. The discussion focuses on the theoretical, social, and political applications of the salutogenic model - and its core concept of SOC - in the context of coping with a global pandemic across different cultural contexts and countries.

The 2021 Magnonics Roadmap.

Magnonics is a budding research field in nanomagnetism and nanoscience that addresses the use of spin waves (magnons) to transmit, store, and process information. The rapid advancements of this field during last one decade in terms of upsurge in research papers, review articles, citations, proposals of devices as well as introduction of new sub-topics prompted us to present the first roadmap on magnonics. This is a collection of 22 sections written by leading experts in this field who review and discuss the current status besides presenting their vision of future perspectives. Today, the principal challenges in applied magnonics are the excitation of sub-100 nm wavelength magnons, their manipulation on the nanoscale and the creation of sub-micrometre devices using low-Gilbert damping magnetic materials and its interconnections to standard electronics. To this end, magnonics offers lower energy consumption, easier integrability and compatibility with CMOS structure, reprogrammability, shorter wavelength, smaller device features, anisotropic properties, negative group velocity, non-reciprocity and efficient tunability by various external stimuli to name a few. Hence, despite being a young research field, magnonics has come a long way since its early inception. This roadmap asserts a milestone for future emerging research directions in magnonics, and hopefully, it will inspire a series of exciting new articles on the same topic in the coming years.

Observation of Magnon Polarization.

We measure the mode-resolved direction of the precessional motion of the magnetic order, i.e., magnon polarization, via the chiral term of inelastic polarized neutron scattering spectra. The magnon polarization is a unique and unambiguous signature of magnets and is important in spintronics, affecting thermodynamic properties such as the magnitude and sign of the spin Seebeck effect. However, it has never been directly measured in any material until this work. The observation of both signs of magnon polarization in Y_{3}Fe_{5}O_{12} also gives direct proof of its ferrimagnetic nature. The experiments agree very well with atomistic simulations of the scattering cross section.

Future directions for the concept of salutogenesis: a position article.

Aaron Antonovsky advanced the concept of salutogenesis almost four decades ago (Antonovsky, Health, Stress and Coping. Jossey-Bass, San Francisco, CA, 1979; Unravelling the Mystery of Health. Jossey-Bass, San Francisco, CA, 1987). Salutogenesis posits that life experiences shape the sense of coherence (SOC) that helps to mobilize resources to cope with stressors and manage tension successfully (determining one's movement on the health Ease/Dis-ease continuum). Antonovsky considered the three-dimensional SOC (i.e. comprehensibility, manageability, meaningfulness) as the key answer to his question about the origin of health. The field of health promotion has adopted the concept of salutogenesis as reflected in the international Handbook of Salutogenesis (Mittelmark et al., The Handbook of Salutogenesis. Springer, New York, 2016). However, health promotion mostly builds on the more vague, general salutogenic orientation that implies the need to foster resources and capacities to promote health and wellbeing. To strengthen the knowledge base of salutogenesis, the Global Working Group on Salutogenesis (GWG-Sal) of the International Union of Health Promotion and Education produced the Handbook of Salutogenesis. During the creation of the handbook and the regular meetings of the GWG-Sal, the working group identified four key conceptual issues to be advanced: (i) the overall salutogenic model of health; (ii) the SOC concept; (iii) the design of salutogenic interventions and change processes in complex systems; (iv) the application of salutogenesis beyond health sector. For each of these areas, we first highlight Antonovsky's original contribution and then present suggestions for future development. These ideas will help guide GWG-Sal's work to strengthen salutogenesis as a theory base for health promotion.

Large magnetic gap at the Dirac point in Bi2Te3/MnBi2Te4 heterostructures.

Magnetically doped topological insulators enable the quantum anomalous Hall effect (QAHE), which provides quantized edge states for lossless charge-transport applications1-8. The edge states are hosted by a magnetic energy gap at the Dirac point2, but hitherto all attempts to observe this gap directly have been unsuccessful. Observing the gap is considered to be essential to overcoming the limitations of the QAHE, which so far occurs only at temperatures that are one to two orders of magnitude below the ferromagnetic Curie temperature, TC (ref. 8). Here we use low-temperature photoelectron spectroscopy to unambiguously reveal the magnetic gap of Mn-doped Bi2Te3, which displays ferromagnetic out-of-plane spin texture and opens up only below TC. Surprisingly, our analysis reveals large gap sizes at 1 kelvin of up to 90 millielectronvolts, which is five times larger than theoretically predicted9. Using multiscale analysis we show that this enhancement is due to a remarkable structure modification induced by Mn doping: instead of a disordered impurity system, a self-organized alternating sequence of MnBi2Te4 septuple and Bi2Te3 quintuple layers is formed. This enhances the wavefunction overlap and size of the magnetic gap10. Mn-doped Bi2Se3 (ref. 11) and Mn-doped Sb2Te3 form similar heterostructures, but for Bi2Se3 only a nonmagnetic gap is formed and the magnetization is in the surface plane. This is explained by the smaller spin-orbit interaction by comparison with Mn-doped Bi2Te3. Our findings provide insights that will be crucial in pushing lossless transport in topological insulators towards room-temperature applications.

Percepción de residentes de pediatría en cuanto a su formación en contenidos transversales. Investigación cualitativa con grupos focales / Perception of residents in pediatrics regarding their training in cross-curricular subjects. Qualitative research in focus groups

Introducción: Los programas de residencia médica son uno de los principales sistemas de formación de especialidades básicas y posbásicas. A partir del análisis "evaluación participativa" de la OPS en 2002 y el informe de la dra. M. Rosa Borrell en 2005, el Ministerio de Salud de la Nación definió bloques transversales en las bases curriculares. Los contenidos transversales abordan problemas centrales del campo de la salud y de la atención, comunes a todas las profesiones médicas. Contextualizan y determinan el ejercicio profesional. El propósito de este trabajo es contribuir a la evaluación del programa de residencias tomando como objeto de interés a los sujetos participantes de las residencias. Objetivo comprender las percepciones de los residentes de Pediatría del Hospital Garrahan sobre la formación en contenidos transversales. Población y métodos. 4 grupos focales, con 4-6 residentes de tercer y cuarto año de pediatría del Hospital Garrahan. Con ejes de discusión previamente planificados, con un tiempo de duración (120 minutos), en un ambiente no directivo, con múltiples disparadores. Análisis: los contenidos de los grupos focales se analizaron a través de la metodología de "teoría fundamentada en los datos" asistido por el programa ATLAS. Ti (versión 8). Resultados. Participaron 20 residentes, con una mediana de edad de 27 +/- 2 años. A partir de los tres ejes de discusión planificados para los grupos focales se elaboraron núcleos temáticos: normativo institucional, programa de formación, dinámicas de aprendizaje, sectores y climas de trabajo, el paciente y su familia, displicencia. En primer lugar, se reconocieron ingresando a una institución con normas de funcionamiento, en donde "la planta" se describió como la figura normativa predominante. En cuanto al programa de formación, hubo satisfacción con las capacidades alcanzadas. Sin embargo, se debatió si el perfil de profesional alcanzado permite reconocer determinantes de salud más allá de las comorbilidades estrictamente médicas. Surgieron problemáticas vinculadas a los límites del modelo médico hegemónico y la necesidad de nuevos enfoques de aprendizaje a través de la problematización del paciente en su contexto social. Definieron los casos clínicos como la mejor forma de abordar el conocimiento sobre un tema. Surgió espontáneamente el tema de la discriminación. Conclusión: a través de los grupos focales, como espacio de escucha activa de la experiencia cotidiana de trabajo de los residentes del Hospital Garrahan surgieron problemáticas vinculadas a los límites del modelo médico hegemónico y la necesidad de enfoques de aprendizaje a través de la problematización del paciente en su contexto social (AU)

Introduction: Medical residency programs are one of the main systems for the training in basic and post-basic specialties. Based on the "participatory evaluation" analysis by the PAHO in 2002 and the report by dr. M. Rosa Borrell in 2005, the National Ministry of Health defined cross-curricular groups to form the basis of the curriculum. The cross-curricular contents address core subjects in the health care field, common to all medical professions. These subjects contextualize and determine the professional practice. The aim of this study was to contribute to the evaluation of the residency program focusing on the participants in the residency programs. Objective: To assess the perceptions of the residents in Pediatric Hospital Garrahan regarding the training and crosscurricular contents. Population and methods: 4 focus groups, with 4-6 residents of the third and fourth year of Pediatrics at Garrahan Hospital using previously determined lines of discussion, in a time slot of 120 minutes, in a non-directive environment, with multiple triggers. Analysis: The contents of the focus groups were analyzed using the "grounded theory data" methodology supported by the ATLAS program, Ti (version 8). Results: 20 residents, with a median age of 27 +/- 2 years, participated in the program. Based on the three discussion lines planned for the focus groups, six core topics were developed: Institutional norms, training program, learning dynamics, sectors and work environments, the patients and their families, displeasure. In the first place, the subjects recognized they entered an institution with its proper norms, in which "the staff" describes itself as the predominant normative figures. Regarding the training program, subjects were satisfied with skills obtained. However, there was debate as to whether the professional profile achieved included knowledge on determining health factors beyond the strictly medical comorbidities. Issues came up related to the limits of the hegemonic model of the physician and the need for new learning targets through the problematization of the patient in his or her social context. Clinical cases were defined as the best way to approach the knowledge on this subject. The subject of discrimination came up spontaneously. Conclusion: Through focus groups, as an active listening space for the experience in the daily practice of the residents at Garrahan Hospital Garrahan, issues appeared related to the limits of the hegemonic model of the physician the need for new learning targets through the problematization of the patient in his or her social context (AU)

Single step, direct fluorescence immunoassays based on metal enhanced fluorescence (MEF-FIA) applicable as micro plate-, array-, multiplexing- or point of care-format.

Although Enzyme Linked Immuno Sorbent Assay (ELISA) technology is approaching it's 45th year of existence since first described in 1971, it is still the main diagnostic tool in clinical research and routine diagnostics. However, despite its broad usage it suffers from some drawbacks, limiting its use especially in more advanced assay formats like multiplexing platforms, point of care devices or protein arrays. Those limitations result from the need for an enzyme label, a soluble enzyme substrate, washing steps (multiplexing, point care, arrays) and in some cases also insufficient sensitivity, because the majority of circulating proteins and thus potential biomarkers may be found in lower sub-picomolar concentrations. We hereby present a new assay platform based on metal enhanced fluorescence (MEF), that remedies these problems since it eliminates the need for washing steps, for using enzyme labels and allows detection of analytes down to sub-picomolar concentrations. In addition this technology is fully compatible to standard fluorescence reader equipment as it is found in many laboratories nowadays. Since our present work is focused on single biomarker evaluation, we chose a 96 well plate format for convenience, but any other formate like antibody arrays, strip-like point of care devices etc. is feasible too.

Negative Longitudinal Magnetoresistance from the Anomalous N=0 Landau Level in Topological Materials.

Negative longitudinal magnetoresistance (NLMR) is shown to occur in topological materials in the extreme quantum limit, when a magnetic field is applied parallel to the excitation current. We perform pulsed and dc field measurements on Pb_{1-x}Sn_{x}Se epilayers where the topological state can be chemically tuned. The NLMR is observed in the topological state, but is suppressed and becomes positive when the system becomes trivial. In a topological material, the lowest N=0 conduction Landau level disperses down in energy as a function of increasing magnetic field, while the N=0 valence Landau level disperses upwards. This anomalous behavior is shown to be responsible for the observed NLMR. Our work provides an explanation of the outstanding question of NLMR in topological insulators and establishes this effect as a possible hallmark of bulk conduction in topological matter.

Observation of the spin Nernst effect.

The observation of the spin Hall effect triggered intense research on pure spin current transport. With the spin Hall effect, the spin Seebeck effect and the spin Peltier effect already observed, our picture of pure spin current transport is almost complete. The only missing piece is the spin Nernst (-Ettingshausen) effect, which so far has been discussed only on theoretical grounds. Here, we report the observation of the spin Nernst effect. By applying a longitudinal temperature gradient, we generate a pure transverse spin current in a Pt thin film. For readout, we exploit the magnetization-orientation-dependent spin transfer to an adjacent yttrium iron garnet layer, converting the spin Nernst current in Pt into a controlled change of the longitudinal and transverse thermopower voltage. Our experiments show that the spin Nernst and the spin Hall effect in Pt are of comparable magnitude, but differ in sign, as corroborated by first-principles calculations.

Influence of tibial hybrid fixation on graft tension and stability in ACL double-bundle reconstruction.

PURPOSE: Initial graft tension in anterior cruciate ligament (ACL) reconstruction affects stability and tension loss at follow-up. This study investigated the influence of hybrid tibial fixation in 3-tunnel double-bundle ACL reconstruction on initial graft tension and tension change and stability under anterior and combined rotatory loads. METHODS: Eleven fresh-frozen cadaveric knees were reconstructed with an ACL double bundle using a 3-tunnel technique. Grafts were tightened to 80 N in 60° (AM bundle) and 15° (PL bundle) of flexion. Anterior tibial translation under 134 N of anterior shear load and translation under combined rotatory and valgus loads (10 Nm valgus stress, 4 Nm internal tibial torque) were determined at 0°, 30°, 60°, and 90° flexion. In addition, graft tension under continuous passive motion was determined. Intact, ACL-resected and ACL-reconstructed joints with either tibial extracortical graft fixation or extracortical plus supplemental aperture graft fixation (hybrid fixation) were tested. RESULTS: Hybrid fixation did not increase graft tension in either bundle during fixation or in motion without additional load. AM-bundle tension increased (p < 0.05) at 0° under combined rotatory and valgus loads and at 30° and 60° under both loading conditions without decreasing the anterior tibial translation. PL-bundle tension increased (p < 0.05) only at 90° under combined rotatory and valgus loads. CONCLUSIONS: Tibial hybrid fixation in 3-tunnel double-bundle ACL reconstruction increases time-zero AM- and PL-bundle tensions under loading conditions, generating greater construct stiffness. This could lead to a longer preservation of ACL-graft stability in clinical follow-up before bony incorporation.

Decrease in mortality of adult epilepsy patients since 1980: lessons learned from a hospital-based cohort.

BACKGROUND AND PURPOSE: Data on mortality in patients with epilepsy have been available since the 1800s. They consistently show a 2-3-fold increase compared to the general population. Despite major advances in diagnostic tools and treatment options, there is no evidence for a decrease in premature deaths. The temporal trend of mortality in a hospital-based epilepsy cohort over three decades was assessed. METHODS: A hospital-based incidence cohort was recruited from a specialized epilepsy outpatient clinic at Innsbruck Medical University between 1980 and 2007, divided by decade into three cohorts and followed for 5 years after initial epilepsy diagnosis. Deaths and their primary causes were determined using probabilistic record linkage with the Austrian death registry. Age-, sex- and period-adjusted standardized mortality rates (SMRs) were computed in relation to the general population of the same area and grouped according to time of diagnosis. RESULTS: In all, 122 deaths in 4549.9 person-years (1954.5 women, 2595.2 men) were identified. The overall SMR was 2.2 [95% confidence interval (CI) 1.8-2.6] and decreased from 3.0 (95% CI 2.1-4.3) in 1980-1989, to 2.7 (95% CI 2.0-3.5) in 1990-1999 and to 1.4 (95% CI 1.0-2.0) in 2000-2007. CONCLUSIONS: This study indicates a decrease in mortality in newly diagnosed epilepsy patients over the last three decades. This may be due to advances in diagnosis and treatment over the past three decades, including early identification of drug resistance, introduction of new anti-epileptic drugs and establishment of a comprehensive epilepsy surgery programme in this region.

Periarticular injections with continuous perfusion of local anaesthetics provide better pain relief and better function compared to femoral and sciatic blocks after TKA: a randomized clinical trial.

PURPOSE: Combined femoral and sciatic nerve blocks for post-operative pain management following total knee arthroplasty (TKA) improve patient satisfaction, decrease narcotic consumption and improve pain. However, accompanying motoric weakness can cause falls and related complications. We wonder whether peri-capsular injections in combination with intra-articular perfusion of local anaesthetics would result in equal or less pain without the related complications of nerve blocks. The objective of the study was to verify these aspects in a prospective randomized trial comparing both treatments. METHODS: Fifty TKA patients randomly received either a femoral (continuous) and a sciatic (single-shot) nerve block (CFNB group, 25 knees) or periarticular infiltrations and a continuous post-operative intra-articular infusion (PIAC group, 25 knees). VAS for pain, pain medication consumption, functional assessment, straight leg raising as well as KSS were recorded post-operatively for 6 days. RESULTS: VAS (p < 0.001) and KSS (p = 0.05) were significantly better for PIAC. There was increased pain following CFNB compared to PIAC. Catheters stayed for 4 days, a pain 'rebound' occurred after removing in CFNB but not after PIAC. There was no difference in regard to knee function (n.s.), but straight leg raising was significant better following PIAC. There were two falls in patients with CFNB. CONCLUSION: Peri-capsular injections combined with an intra-articular catheter provide better pain control, no rebound pain with better function and might decrease the risk of complications related to motor weakness. LEVEL OF EVIDENCE: I.

Observation of temperature-gradient-induced magnetization.

Applying magnetic fields has been the method of choice to magnetize non-magnetic materials, but they are difficult to focus. The magneto-electric effect and voltage-induced magnetization generate magnetization by applied electric fields, but only in special compounds or heterostructures. Here we demonstrate that a simple metal such as gold can be magnetized by a temperature gradient or magnetic resonance when in contact with a magnetic insulator by observing an anomalous Hall-like effect, which directly proves the breakdown of time-reversal symmetry. Such Hall measurements give experimental access to the spectral spin Hall conductance of the host metal, which is closely related to other spin caloritronics phenomena such as the spin Nernst effect and serves as a reference for theoretical calculation.

Massive and massless Dirac fermions in Pb1-xSnxTe topological crystalline insulator probed by magneto-optical absorption.

Dirac fermions in condensed matter physics hold great promise for novel fundamental physics, quantum devices and data storage applications. IV-VI semiconductors, in the inverted regime, have been recently shown to exhibit massless topological surface Dirac fermions protected by crystalline symmetry, as well as massive bulk Dirac fermions. Under a strong magnetic field (B), both surface and bulk states are quantized into Landau levels that disperse as B(1/2), and are thus difficult to distinguish. In this work, magneto-optical absorption is used to probe the Landau levels of high mobility Bi-doped Pb0.54Sn0.46Te topological crystalline insulator (111)-oriented films. The high mobility achieved in these thin film structures allows us to probe and distinguish the Landau levels of both surface and bulk Dirac fermions and extract valuable quantitative information about their physical properties. This work paves the way for future magnetooptical and electronic transport experiments aimed at manipulating the band topology of such materials.