Experimental Realization of a Three-Dimensional Dirac Semimetal Phase with a Tunable Lifshitz Transition in Au_{2}Pb.

Three-dimensional Dirac semimetals are an exotic state of matter that continue to attract increasing attention due to the unique properties of their low-energy excitations. Here, by performing angle-resolved photoemission spectroscopy, we investigate the electronic structure of Au_{2}Pb across a wide temperature range. Our experimental studies on the (111)-cleaved surface unambiguously demonstrate that Au_{2}Pb is a three-dimensional Dirac semimetal characterized by the presence of a bulk Dirac cone projected off-center of the bulk Brillouin zone (BZ), in agreement with our theoretical calculations. Unusually, we observe that the bulk Dirac cone is significantly shifted by more than 0.4 eV to higher binding energies with reducing temperature, eventually going through a Lifshitz transition. The pronounced downward shift is qualitatively reproduced by our calculations indicating that an enhanced orbital overlap upon compression of the lattice, which preserves C_{4} rotational symmetry, is the main driving mechanism for the Lifshitz transition. These findings not only broaden the range of currently known materials exhibiting three-dimensional Dirac phases, but also show a viable mechanism by which it could be possible to switch on and off the contribution of the degeneracy point to electron transport without external doping.

On the problem of Dirac cones in fullerenes on gold.

Artificial graphene based on molecular networks enables the creation of novel 2D materials with unique electronic and topological properties. Landau quantization has been demonstrated by CO molecules arranged on the two-dimensional electron gas on Cu(111) and the observation of electron quantization may succeed based on the created gauge fields. Recently, it was reported that instead of individual manipulation of CO molecules, simple deposition of nonpolar C60 molecules on Cu(111) and Au(111) produces artificial graphene as evidenced by Dirac cones in photoemission spectroscopy. Here, we show that C60-induced Dirac cones on Au(111) have a different origin. We argue that those are related to umklapp diffraction of surface electronic bands of Au on the molecular grid of C60 in the final state of photoemission. We test this alternative explanation by precisely probing the dimensionality of the observed conical features in the photoemission spectra, by varying both the incident photon energy and the degree of charge doping via alkali adatoms. Using density functional theory calculations and spin-resolved photoemission we reveal the origin of the replicating Au(111) bands and resolve them as deep leaky surface resonances derived from the bulk Au sp-band residing at the boundary of its surface projection. We also discuss the manifold nature of these resonances which gives rise to an onion-like Fermi surface of Au(111).

Mortality trends from central nervous system tumors in the seven socioeconomic regions and thirty-two states of Mexico from 2000 until 2017. / Tendencias de mortalidad por tumores del sistema nervioso central en las siete regiones socioeconómicas y en los 32 estados de México entre 2000 y 2017.

INTRODUCTION: Central nervous system (CNS) tumors are a public health problem worldwide. In Mexico in 2018, occupied 17th in cancer incidence, that same year ranking 13th among causes of cancer mortality. The aim of this study was to determine mortality trends from (CNS) tumors, nationwide by state and socioeconomic region and determine the risk of died from (CNS) tumors according to the level of education in the period 2000-2017. MATERIALS AND METHODS: Mortality records associates to central nervous system tumors were obtained of the National Institute of Statistics and Geography for the period 2000-2017. Mortality rates were calculated at the national level, by state, and socioeconomic region, the strength of association between educational level with the mortality from (CNS) tumors was also calculated. RESULTS: In the years 2000-2017, age-adjusted mortality rates to the world population per 100,000 inhabitants increased from 1.9 to 2.1. A male/female ratio was 1:2. The 65-69 age group had the highest number of deaths with 3,370 (9.8%). CONCLUSIONS: In the study period age-adjusted mortality rates per 100,000 habitants increased from 1.9 to 2.1. Individuals without school or incomplete elementary school had a higher risk of died from (CNS) tumors. The region socioeconomic 6 and 7 had the highest mortality rates from (CNS) tumors.

TITLE: Tendencias de mortalidad por tumores del sistema nervioso central en las siete regiones socioeconómicas y en los 32 estados de México entre 2000 y 2017.Introducción. Los tumores del sistema nervioso central (SNC) son un problema de salud pública en el mundo. En México, en 2018, ocuparon el número 17 en incidencia de cáncer. Ese mismo año ocuparon el número 13 entre las causas de mortalidad por cáncer. El objetivo de este estudio fue determinar las tendencias de mortalidad por tumores del SNC a nivel nacional por estado y región socioeconómica, y determinar el riesgo de muerte por tumores del SNC según el nivel de escolaridad en el período 2000-2017. Materiales y métodos. Se obtuvieron del Instituto Nacional de Estadística y Geografía los registros de mortalidad asociados a tumores del SNC para el período 2000-2017. Las tasas de mortalidad se calcularon a nivel nacional, por estado y región socioeconómica, y también se calculó la fuerza de asociación entre el nivel educativo con la mortalidad por tumores del SNC. Resultados. En los años 2000-2017, las tasas de mortalidad ajustadas por edad de la población mundial por cada 100.000 habitantes se incrementaron de 1,9 a 2,1. La proporción hombre/mujer fue de 1:2. El grupo de 65 a 69 años tuvo el mayor número de muertes, con 3.370 (9,8%). Conclusiones. En el período de estudio, las tasas de mortalidad ajustadas por edad por cada 100.000 habitantes aumentaron de 1,9 a 2,1. Las personas sin escolaridad o con escuela primaria no terminada tuvieron mayor riesgo de morir por tumores del SNC. Las regiones socioeconómicas 6 y 7 tuvieron las tasas de mortalidad más altas.

Tendencias de mortalidad por tumores del sistema nervioso central en las siete regiones socioeconómicas y en los 32 estados de México entre 2000 y 2017 / Mortality trends from central nervous system tumors in the seven socioeconomic regions and thirty-two states of Mexico from 2000 until 2017

Introducción: Los tumores del sistema nervioso central (SNC) son un problema de salud pública en el mundo. En México, en 2018, ocuparon el número 17 en incidencia de cáncer. Ese mismo año ocuparon el número 13 entre las causas de mortalidad por cáncer. El objetivo de este estudio fue determinar las tendencias de mortalidad por tumores del SNC a nivel nacional por estado y región socioeconómica, y determinar el riesgo de muerte por tumores del SNC según el nivel de escolaridad en el período 2000-2017. Materiales y métodos: Se obtuvieron del Instituto Nacional de Estadística y Geografía los registros de mortalidad asociados a tumores del SNC para el período 2000-2017. Las tasas de mortalidad se calcularon a nivel nacional, por estado y región socioeconómica, y también se calculó la fuerza de asociación entre el nivel educativo con la mortalidad por tumores del SNC. Resultados: En los años 2000-2017, las tasas de mortalidad ajustadas por edad de la población mundial por cada 100.000 habitantes se incrementaron de 1,9 a 2,1. La proporción hombre/mujer fue de 1:2. El grupo de 65 a 69 años tuvo el mayor número de muertes, con 3.370 (9,8%). Conclusiones: En el período de estudio, las tasas de mortalidad ajustadas por edad por cada 100.000 habitantes aumentaron de 1,9 a 2,1. Las personas sin escolaridad o con escuela primaria no terminada tuvieron mayor riesgo de morir por tumores del SNC. Las regiones socioeconómicas 6 y 7 tuvieron las tasas de mortalidad más altas.(AU)

Introduction: Central nervous system (CNS) tumors are a public health problem worldwide. In Mexico in 2018, occupied 17th in cancer incidence, that same year ranking 13th among causes of cancer mortality. The aim of this study was to determine mortality trends from (CNS) tumors, nationwide by state and socioeconomic region and determine the risk of died from (CNS) tumors according to the level of education in the period 2000-2017. Materials and methods: Mortality records associates to central nervous system tumors were obtained of the National Institute of Statistics and Geography for the period 2000-2017. Mortality rates were calculated at the national level, by state, and socioeconomic region, the strength of association between educational level with the mortality from (CNS) tumors was also calculated. Results. In the years 2000-2017, age-adjusted mortality rates to the world population per 100,000 inhabitants increased from 1.9 to 2.1. A male/female ratio was 1:2. The 65-69 age group had the highest number of deaths with 3,370 (9.8%). Conclusions: In the study period age-adjusted mortality rates per 100,000 habitants increased from 1.9 to 2.1. Individuals without school or incomplete elementary school had a higher risk of died from (CNS) tumors. The region socioeconomic 6 and 7 had the highest mortality rates from (CNS) tumors.(AU)

Cubic Rashba Effect in the Surface Spin Structure of Rare-Earth Ternary Materials.

Spin-orbit interaction and structure inversion asymmetry in combination with magnetic ordering is a promising route to novel materials with highly mobile spin-polarized carriers at the surface. Spin-resolved measurements of the photoemission current from the Si-terminated surface of the antiferromagnet TbRh_{2}Si_{2} and their analysis within an ab initio one-step theory unveil an unusual triple winding of the electron spin along the fourfold-symmetric constant energy contours of the surface states. A two-band k·p model is presented that yields the triple winding as a cubic Rashba effect. The curious in-plane spin-momentum locking is remarkably robust and remains intact across a paramagnetic-antiferromagnetic transition in spite of spin-orbit interaction on Rh atoms being considerably weaker than the out-of-plane exchange field due to the Tb 4f moments.

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.

Prediction and observation of an antiferromagnetic topological insulator.

Magnetic topological insulators are narrow-gap semiconductor materials that combine non-trivial band topology and magnetic order1. Unlike their nonmagnetic counterparts, magnetic topological insulators may have some of the surfaces gapped, which enables a number of exotic phenomena that have potential applications in spintronics1, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3. So far, magnetic topological insulators have only been created by means of doping nonmagnetic topological insulators with 3d transition-metal elements; however, such an approach leads to strongly inhomogeneous magnetic4 and electronic5 properties of these materials, restricting the observation of important effects to very low temperatures2,3. An intrinsic magnetic topological insulator-a stoichiometric well ordered magnetic compound-could be an ideal solution to these problems, but no such material has been observed so far. Here we predict by ab initio calculations and further confirm using various experimental techniques the realization of an antiferromagnetic topological insulator in the layered van der Waals compound MnBi2Te4. The antiferromagnetic ordering  that MnBi2Te4  shows makes it invariant with respect to the combination of the time-reversal and primitive-lattice translation symmetries, giving rise to a ℤ2 topological classification; ℤ2 = 1 for MnBi2Te4, confirming its topologically nontrivial nature. Our experiments indicate that the symmetry-breaking (0001) surface of MnBi2Te4 exhibits a large bandgap in the topological surface state. We expect this property to eventually enable the observation of a number of fundamental phenomena, among them quantized magnetoelectric coupling6-8 and axion electrodynamics9,10. Other exotic phenomena could become accessible at much higher temperatures than those reached so far, such as the quantum anomalous Hall effect2 and chiral Majorana fermions3.

Samarium hexaboride is a trivial surface conductor.

SmB6 is predicted to be the first member of the intersection of topological insulators and Kondo insulators, strongly correlated materials in which the Fermi level lies in the gap of a many-body resonance that forms by hybridization between localized and itinerant states. While robust, surface-only conductivity at low temperature and the observation of surface states at the expected high symmetry points appear to confirm this prediction, we find both surface states at the (100) surface to be topologically trivial. We find the [Formula: see text] state to appear Rashba split and explain the prominent [Formula: see text] state by a surface shift of the many-body resonance. We propose that the latter mechanism, which applies to several crystal terminations, can explain the unusual surface conductivity. While additional, as yet unobserved topological surface states cannot be excluded, our results show that a firm connection between the two material classes is still outstanding.

Strong Spin Dependence of Correlation Effects in Ni Due to Stoner Excitations.

Using high-resolution angle-resolved photoemission, we observe a strong spin-dependent renormalization and lifetime broadening of the quasiparticle excitations in the electronic band structure of Ni(111) in an energy window of ∼0.3 eV below the Fermi level. We derive a quantitative result for the spin-dependent lifetime broadening by comparing the scattering rates of majority and minority d states, and further show that spin-dependent electron correlations are instead negligible for sp states. From our analysis we experimentally determine the effective on-site Coulomb interaction U caused by Stoner-like interband transitions between majority and minority d states. The present results demonstrate the remarkable impact of spin-dependent electron correlation effects originating from single-particle excitations in a prototypical 3d transition metal, paving the way for further refinement of current many-body theoretical approaches.

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.

Giant Magnetic Band Gap in the Rashba-Split Surface State of Vanadium-Doped BiTeI: A Combined Photoemission and Ab Initio Study.

One of the most promising platforms for spintronics and topological quantum computation is the two-dimensional electron gas (2DEG) with strong spin-orbit interaction and out-of-plane ferromagnetism. In proximity to an s-wave superconductor, such 2DEG may be driven into a topologically non-trivial superconducting phase, predicted to support zero-energy Majorana fermion modes. Using angle-resolved photoemission spectroscopy and ab initio calculations, we study the 2DEG at the surface of the vanadium-doped polar semiconductor with a giant Rashba-type splitting, BiTeI. We show that the vanadium-induced magnetization in the 2DEG breaks time-reversal symmetry, lifting Kramers degeneracy of the Rashba-split surface state at the Brillouin zone center via formation of a huge gap of about 90 meV. As a result, the constant energy contour inside the gap consists of only one circle with spin-momentum locking. These findings reveal a great potential of the magnetically-doped semiconductors with a giant Rashba-type splitting for realization of novel states of matter.

Mortality trends and risk of dying from colorectal cancer in the seven socioeconomic regions of Mexico, 2000-2012. / Tendencias de mortalidad y riesgo de muerte por cáncer colorrectal en las 7 regiones socioeconómicas de México, 2000-2012.

BACKGROUND: In Mexico, there has been an upward trend in mortality rates from colorectal cancer (CRC) over the past three decades. This tumor is ranked among the ten most prevalent causes of morbidity from malignancies in Mexico. AIMS: To determine the mortality trends by socioeconomic region and by state, and to establish the relative risk between both educational level and socioeconomic region with mortality from CRC within the time frame of 2000-2012. MATERIALS AND METHODS: Records of mortality associated with colorectal cancer were obtained. Rates of mortality by state and by socioeconomic region were calculated, along with the strength of association (obtained through the Poisson regression) between both socioeconomic region and educational level and the mortality from CRC. RESULTS: A total of 45,487 individuals died from CRC in Mexico from 2000 to 2012. Age-adjusted mortality rates per 100,000 inhabitants increased from 3.9 to 4.8. Baja California, Baja California Sur, and Sonora had the highest mortality from CRC. Individuals with no school or incomplete elementary school had a higher risk of dying from this cancer (RR of 3.57, 95% CI: 3.46-3.68). Region 7 had the strongest association with mortality from CRC (Mexico City: RR was 2.84, 95% CI: 2.39-3.37 [2000] and 3.32, 95% CI: 2.89-3.82 [2012]). CONCLUSIONS: In Mexico, the age-adjusted mortality rates per 100,000 inhabitants that died from CRC increased from 3.9 to 4.8 in the study period, using the world population age distribution as the standard. Baja California, Baja California Sur, and Sonora had the highest mortality from CRC. Mexico City, which was socioeconomic region 7, had the strongest association with mortality from CRC.

Tailoring the nature and strength of electron-phonon interactions in the SrTiO3(001) 2D electron liquid.

Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO3(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO3/SrTiO3 interface, our angle-resolved photoemission data show replica bands separated by 100 meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies long-range coupling to a single longitudinal optical phonon branch. In the overdoped regime the preferential coupling to this branch decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow a unified understanding of the transport properties in SrTiO3-based 2DELs.

Mortality trends and years of potential life lost from gastric cancer in Mexico, 2000-2012. / Tendencias de mortalidad y años potenciales de vida perdidos por cáncer gástrico en México, 2000-2012.

BACKGROUND: In 2013 in Mexico, gastric cancer (GC) was the third leading cause of death from cancer in individuals 20 years of age or older. GC remains a public health problem in Mexico due to its high mortality and low survival rates, and the significantly lower quality of life of patients with this condition. OBJECTIVES: The aims of this study were to determine mortality trends nationwide, by state and socioeconomic region, and to determine rates of age-adjusted years of potential life lost due to GC, by state and socioeconomic region, within the period of 2000-2012. METHODS: Mortality records associated with GC for 2000-2012 were obtained from the National Health Information System of the Mexican Department of Health. Codes from the Tenth Revision of the International Classification of Diseases corresponding to the basic cause of death from GC were identified. Mortality and age-adjusted years of potential life lost rates, by state and socioeconomic region, were also calculated. RESULTS: In Mexico, 69,107 individuals died from GC within the time frame of 2000-2012. The age-adjusted mortality rate per 100,000 inhabitants decreased from 7.5 to 5.6. The male:female ratio was 1.15:1.0. Chiapas had the highest death rate from GC (9.2, 95% CI 8.2-10.3 [2000] and 8.2, 95% CI 7.3-9 [2012]), as well as regions 1, 2, and 5. Chiapas and socioeconomic region 1 had the highest rate of years of potential life lost. CONCLUSIONS: Using the world population age distribution as the standard, the age-adjusted mortality rate in Mexico per 100,000 inhabitants that died from GC decreased from 7.5 to 5.6 between 2000 and 2012. Chiapas and socioeconomic regions 1, 2, and 5 had the highest mortality from GC (Chiapas: 9.2, 95% CI 8.2-10.3 [2000] and 8.2, 95% CI 7.3-9 [2012], region 1: 5.5, 95% CI 5.2-5.9 [2000] and 5.3, 95% CI 4.9-5.7 [2012]; region 2: 5.3, 95% CI 5-5.6 [2000] and 5.4, 95% CI 5.1-5.8 [2012]; region 5: 6.1, 95% CI 5.6-6.6 [2000] and 4.6, 95% CI 4.2-5 [2012]). Chiapas and socioeconomic region 1 had the highest rate of years of potential life lost (Chiapas: 97.4 [2000] and 79.6 [2012] and region 1: 73.5 [2000] 65 [2012]).

Nonmagnetic band gap at the Dirac point of the magnetic topological insulator (Bi(1-x)Mn(x))2Se3.

Magnetic doping is expected to open a band gap at the Dirac point of topological insulators by breaking time-reversal symmetry and to enable novel topological phases. Epitaxial (Bi(1-x)Mn(x))2Se3 is a prototypical magnetic topological insulator with a pronounced surface band gap of ∼100 meV. We show that this gap is neither due to ferromagnetic order in the bulk or at the surface nor to the local magnetic moment of the Mn, making the system unsuitable for realizing the novel phases. We further show that Mn doping does not affect the inverted bulk band gap and the system remains topologically nontrivial. We suggest that strong resonant scattering processes cause the gap at the Dirac point and support this by the observation of in-gap states using resonant photoemission. Our findings establish a mechanism for gap opening in topological surface states which challenges the currently known conditions for topological protection.

Tunable Fermi level and hedgehog spin texture in gapped graphene.

Spin and pseudospin in graphene are known to interact under enhanced spin-orbit interaction giving rise to an in-plane Rashba spin texture. Here we show that Au-intercalated graphene on Fe(110) displays a large (∼230 meV) bandgap with out-of-plane hedgehog-type spin reorientation around the gapped Dirac point. We identify two causes responsible. First, a giant Rashba effect (∼70 meV splitting) away from the Dirac point and, second, the breaking of the six-fold graphene symmetry at the interface. This is demonstrated by a strong one-dimensional anisotropy of the graphene dispersion imposed by the two-fold-symmetric (110) substrate. Surprisingly, the graphene Fermi level is systematically tuned by the Au concentration and can be moved into the bandgap. We conclude that the out-of-plane spin texture is not only of fundamental interest but can be tuned at the Fermi level as a model for electrical gating of spin in a spintronic device.

Reversal of the circular dichroism in angle-resolved photoemission from Bi2Te3.

The helical Dirac fermions at the surface of topological insulators show a strong circular dichroism which has been explained as being due to either the initial-state spin angular momentum, the initial-state orbital angular momentum, or the handedness of the experimental setup. All of these interpretations conflict with our data from Bi(2)Te(3) which depend on the photon energy and show several sign changes. Our one-step photoemission calculations coupled to ab initio theory confirm the sign change and assign the dichroism to a final-state effect. Instead, the spin polarization of the photoelectrons excited with linearly polarized light remains a reliable probe for the spin in the initial state.

The graphene/Au/Ni interface and its application in the construction of a graphene spin filter.

A modification of the contact of graphene with ferromagnetic electrodes in a model of the graphene spin filter allowing restoration of the graphene electronic structure is proposed. It is suggested for this aim to intercalate into the interface between the graphene and the ferromagnetic (Ni or Co) electrode a Au monolayer to block the strong interaction between the graphene and Ni (Co) and, thus, prevent destruction of the graphene electronic structure which evolves in direct contact of graphene with Ni (Co). It is also suggested to insert an additional buffer graphene monolayer with the size limited by that of the electrode between the main graphene sheet providing spin current transport and the Au/Ni electrode injecting the spin current. This will prevent the spin transport properties of graphene from influencing contact phenomena and eliminate pinning of the graphene electronic structure relative to the Fermi level of the metal, thus ensuring efficient outflow of injected electrons into the graphene. The role of the spin structure of the graphene/Au/Ni interface with enhanced spin-orbit splitting of graphene π states is also discussed, and its use is proposed for additional spin selection in the process of the electron excitation.

Tolerance of topological surface states towards magnetic moments: Fe on Bi2Se3.

We study the effect of Fe impurities deposited on the surface of the topological insulator Bi(2)Se(3) by means of core-level and angle-resolved photoelectron spectroscopy. The topological surface state reveals surface electron doping when the Fe is deposited at room temperature and hole doping with increased linearity when deposited at low temperature (~8 K). We show that in both cases the surface state remains intact and gapless, in contradiction to current belief. Our results suggest that the surface state can very well exist at functional interfaces with ferromagnets in future devices.

Ir(111) surface state with giant Rashba splitting persists under graphene in air.

We reveal a giant Rashba effect (α(R)≈1.3 eV Å) on a surface state of Ir(111) by angle-resolved photoemission and by density functional theory. It is demonstrated that the existence of the surface state, its spin polarization, and the size of its Rashba-type spin-orbit splitting remain unaffected when Ir is covered with graphene. The graphene protection is, in turn, sufficient for the spin-split surface state to survive in ambient atmosphere. We discuss this result along with indications for a topological protection of the surface state.