Best Research of 2017

Report Number: 196

New Fractional Quantum Hall States in Ultra-Clean Graphene Heterostructures

Spanton E.M. (UCSB, CNSI); Zibrov, A.A.; Zhou, H., Kometter, C., Young, A.F. (UCSB, Physics)
Published in: A. A. Zibrov et al., Nature 549, 360–364 (2017)

In monolayer graphene, a new transition leading to the weakening of the odd-denominator fractional quantum Hall (FQH) states which nearly coincides with the emergence of unexpected even denominator states, is observed. The even-denominator states result from pairing between electrons living on different sub-lattices and are a new manifestation of a multi-component FQH effect.

Report Number: 335

Integer and Fractional Quantum Hall effect in Ultra-high Quality Few-layer Black Phosphorus Transistors

Yang, J., Tran, S., Che, S., Stepanov, P., Chen, R., Lau, C.N. (The Ohio State University); Wu, J. (University of California, Riverside); Watanabe, K., Taniguchi, T. (NIMS); Baek, H. and Smirnov, D. (National MagLab)
Published in: J. Yang et al., Nano Lett. 18, 229–234 (2018)

A fractional quantum-Hall (FQHE) state is observed at filling factors nu~-4/3 and nu~-0.56 ± 0.1 in high mobility black phosphorus samples. This is first observation of FQHE in a non-graphene 2D material.

Report Number: 357

Probing mixed spin singlet-triplet Cooper pairs in 2D NbSe₂ under high magnetic fields

Sohn E., Xi, X., Wang, Z., Jiang, S., Shan, J., Mak, K.F.; Park, J.-H.; Law, K.T.; Berger, H., Forro, L.
Published in: Nature Materials volume 17, pages504–508 (2018)

2D crystals extracted from transition-metal dichalcogenides represent a new platform for exploring collective quantum phenomena, such as an unconventional superconductivity that arises from strong spin-orbit interaction and broken inversion symmetry. By using tunneling spectroscopy, Sohn et al. observe a continuous closing of the superconducting gap in 2D NbSe₂ by an in-plane magnetic field. The results provide strong evidence for the presence of the asymmetric Ising spin-orbit coupling.

Report Number: 174

Transport of dilute MgZnO/ZnO heterostructures

Falson, J., Tabrea, D., Smet, J.H.

The quantum Hall-effect led to the development of a series of fundamental physical concepts, ranging from the role of topology in electronic systems, to the idea of 'braiding" non-Abelian quasiparticles with the aim of developing quantum computers. Traditionally, the highest quality two-dimensional gas, that is the one subjected to weakest disorder potential, was achieved at the interface between GaAs and Al_xGa_1-xAs grown via molecular beam epitaxy (MBE), which was shown to display carrier mobilities as high as 30 x 10⁶ cm2/Vs. It is therefore remarkable that another series of heterostructures based upon MgZnO and ZnO also grown by MBE but using oxygen plasma as the oxidizing agent, have just been found by this group to display mobilities approaching 1.2 x 10⁶ cm²/Vs. They have produced extremely low carrier density samples, already observing integer and fractional quantum Hall states at relatively low fields. The very high Wigner –Seitz radio, coupled to their high mobilities, should lead to instabilities, such as ferromagnetism or Wigner crystallization, opening unique opportunities for the physics of quantum Hall systems.

Report Number: 255

Unusual interlayer quantum transport caused by the zeroth Landau level in YbMnBi₂

Liu, J.Y., Hu, J., Mao, Z.Q. (Tulane U., Physics); Graf, D. (NHMFL); Zou, T. Zhu, M. Ke, X. (MSU, Physics); Shi, Y., Che, S., Lau, C.N. (Ohio State U., Physics); Radmanesh, S.M.A., Spinu, L. (U. New Orleans, Physics); Cao, H.B. (Oak Ridge)
Published in: J.Y. Liu et al., Nature Communications 8, 646 (2017).

YbMnBi₂ is thought to be a topological quantum material, with Dirac-like bands that exhibit a linear energy momentum relationship close to the Fermi energy, and, in magnetic field, a zeroth Landau level pinned to the band crossing. As crystals of YbMnBi₂ are tilted in the large magnetic fields, their interlayer resistance rises and then peaks sharply when the field lies parallel to the layers; these data are reminiscent of the “interlayer peak” used in the previous decade to demonstrate that quasi-two-dimensional superconductors in fact possess three-dimensional Fermi surfaces. The mechanism in the present case is very closely related, and the magnetoresistance peaks can be modelled using interlayer tunneling of Weyl fermions between zeroth Landau levels.

Report Number: 375

Violation of Ohm's law in Weyl metal Bi_1-xSb_x

Shin, D.W., Kim, J.H. (POSTECH, Physics)
Published in: D. Shin et al., Nature Materials 16, 1096–1099 (2017).

Non-linear current-voltage characteristics are observed in Bi_0.96Sb_0.04 but only for fields aligned along the electrical currents and ascribed to the so-called chiral anomaly, which corresponds to the suppression of the chiral symmetry among Weyl fermions. Therefore, topological Weyl semi-metals would violate the Ohm’s law when one induces chiral charge pumping between Weyl points.

Report Number: 9

Direct observation of Landau level resonance and mass generation in Dirac semimetal Cd₃As₂ thin films

Yuan, X., Zhang, C., Song, C., Yan, H. and Xiu, F. (Fudan University, Physics)
Published in: X. Yuan et al., Nano Lett. 17, 2211 (2017); C. Zhang et al., Nat. Commun. 8, 1272 (2017).

The authors observe through magneto-infrared spectroscopy in nano-plates of Cd₃As₂ that landau their Levels do display a B^1/2 dependence as expected for a relativitistic Dirac system. Doping with Cr is found to break the C4 symmetry of the underlying lattice, opening a gap at the Dirac node location. Hence, Cr induces transition from a topologically non-trivial Dirac fermion to a trivial massive fermion state in Cd₃As₂. In these same nano-plates but characterized by a rather low carrier density, the authors observe a higher Shubnikov de Haas frequency with respect to the one detected in the bulk which they find to display a two-dimensional character. This implies that this orbit is associated with the surface of the material, which is further confirmed by the observation of nearly quantized Hall plateaus. These observations might result from the so-called Weyl orbit, where electrons on a surface Fermi arc tunnel through the bulk towards the Fermi arc on the opposite surface, although more theoretical work is needed to understand these observations.

Report Number: 116

Bulk-band Inversion and Three-dimensional Massive Dirac Fermions in ZrTe₅

Chen, Z.-G. (Chinese Academy of Sciences, Institute of Physics); Chen, R.Y. (Peking University, Physics); Zhong, R.D. (Brookhaven National Lab, Physics); Schneeloch, J., Zhang C. (Brookhaven National Lab, Physics); Huang, Y. (Brookhaven National Lab, Functional Nanomaterials), Qu, F. (Chinese Academy of Sciences, IOP); Yu, R. (Wuhan University, Physics); Li, Q., Gu, G.D. (Brookhaven National Lab, Physics) and Wang, N. L. (Peking University, Physics)
Published in: Z-G. Chen et al, Proc. Natl. Acad. Sci. USA 114, 816 (2017).

The authors report an infrared transmission study on high-mobility multilayer ZrTe₅, a compound which was recently predicted to be a topological insulator, under magnetic fields up to 35 T. In the past, the majority of the theoretically predicted topological insulators were verified by detecting their topological surface states. But by studying the optical transitions between bulk Landau levels (LLs), the authors claim to not only find spectroscopic evidence for the bulk-band inversion—the crossing of the two zeroth LLs in a magnetic field, but also quantitatively demonstrate the existence of three-dimensional massive Dirac fermions with nearly linear band dispersions in ZrTe₅.

Report Number: 362

Field-induced nematicity in CeRhIn₅

Shirer, K.R., Bachmann, M.D., Helm, T., Modic, K.A., Moll, P.J.W (Max Planck Institute for Chemical Physics of Solids, Dresden, Germany) Balicas, L., Chan, M., McDonald, R.D., Balakirev, F.F., Jaime, M. (National MagLab), Ramshaw, B.J. (National MagLab/Cornell University), Bauer, E.D. Ronning, F.F. (Los Alamos National Laboratory)
Published in: F. Ronning et al., Nature 548, 313–317 (2017)

This report presents experimental evidence for a field-induced fluctuating nematic phase in the heavy-fermion superconductor CeRhIn5 which is observed in the vicinity of a field-tuned antiferromagnetic quantum critical point around Hc ≈ 50 T. This phase appears above an out-of-plane critical field H*≈28 T and is characterized by a substantial in-plane resistivity anisotropy in the presence of a small in-plane field component with no apparent connection to the underlying lattice according to magnetostriction, or to metamagnetism according to magnetic torque. The authors argue that the appearance of nematic behavior in a prototypical heavy-fermion superconductor highlights the interrelation of nematicity and unconventional superconductivity, suggesting nematicity to be a common feature among correlated materials.

Report Number: 28

Magnetoelectric coupling in Ni₃TeO₆

Musfeldt, J.L., Yokosuk, M.O., O'Neal, K.R. (Tennessee); Yang, J., Oh,Y.S., Kim, H.-.S., Haule, K., Cheong, S.W., Vanderbilt, D. (Rutgers), and Crooker, S. (LANL)

Ni₃TeO₆ shows one of the largest non-hysteretic magnetoelectric couplings, e.g. a large magnetic field-induced electric polarization change. Such coupling has important future applications to low-power electronics and magnetic sensors, smart devices, antennas and others. Ni₃TeO₆ is an example of a material combining 3d magnetic ions with heavier elements like tellurium that can contribute to spin orbit coupling. In this material, the microscopic origin of the magnetoelectric coupling is being tested using optical absorption measurements in pulsed field, which shows the suppression of a certain vibration mode at the magnetic field-induced electric polarization change near 50 T. This data provides an important input to theoretical modeling to understand how the magnetic order affects the lattice to in turn modify electric polarization.

Report Number: 203

Thermal conductivity and magnetic torque study in the honeycomb magnets

Lee, M., Leahy, I.A., Pocs, C.A., Siegfried, P.E. (University of Colorado Boulder); Graf, D. (National High Magnetic Field Laboratory)
Published in: I. Leahy et al, Phys. Rev. Lett. 118, 187203 (2017)

Magnetic spin liquids are a fascinating state of matter in which there are strong interactions among the spins, but they do not form static order. The resulting dynamic and sometimes topological state challenges our understanding of what it means to “order”. As can be imagined, it is difficult to identify and characterize and identify such a spin liquid. In this paper, the authors use careful measurements of torque and thermal conductivity to identify the characteristics of excitations from the spin liquid state that forms in applied magnetic fields.

Report Number: 130

Quantum oscillations in the high pressure metallised Mott insulator NiS₂

Baglo, J., Semeniuk, K., Chang, H. (U. Cambridge UK, Cavendish Laboratory); Friedemann, S. (U. Bristol UK, HH Wills Laboratory); Grockowiack, A., Coniglio, W., Tozer, S. (National MagLab Tallahassee); Grosche, F.M. (U. Cambridge UK, Cavendish Laboratory)

It has been a long-standing aspiration to extend fermiology measurements to pressures in excess of 3 GPa, because this allows researchers to examine correlated electron materials in regions of parameter space which are especially interesting, such as the threshold of magnetism or the vicinity of a metal-insulator transition. This report describes the culmination of a long-running initiative to carry out such high pressure electronic structure measurements in NiS₂, an insulator which is driven into a correlated metallic state under applied pressure. Quantum oscillations were detected over a wide pressure range enabling the team to track the evolution of the electronic Fermi surface and the carrier mass as the system approaches the insulating state.

Report Number: 250

Pressure dependence of the Fermi surface of the nematic superconductor, FeSe_0.89S_0.11

Reiss, P.; Coldea, A.I.; Haghighirad, A.-A. (Clarendon Laboratory, Oxford Physics, UK); Graf. D (National MagLab, Tallahassee)
Published in: Coldea et al., Manuscript in preparation

Coldea et al explore the rich phase diagram of the nematic superconducting family FeSe_xS_1-x by tuning superconductivity via the application of hydrostatic pressure, whilst using the highest available DC magnetic fields to probe the associated changes to the Fermi surface. Unconventional superconductivity is ubiquitously associated with the proximity of some form of long range order–at ambient pressure the long range order in this iron-based superconductor is not magnetic, but a spontaneous lowering of the inplane electronic symmetry. The application of pressure suppress this nematic order in favor of magnetism, strengthening the superconductivity. The associated changes in in the Fermi surface measured by high field quantum oscillation measurements reveal the driving force behind the interplay of nematicity, magnetism and superconductivity.

Report Number: 382

Nematic superconductivity under pressure in CeRhIn₅

Helm, T. and Moll, P.J.W. (Max Planck Institute CPFS); Grockoviak, A.D. and Tozer, S. (National MagLab Tallahassee) Balakirev, F. (National MagLab Los Alamos) Ronning, F. and Bauer, E.D. (Los Alamos National Laboratory)

The Ce115 heavy Fermion (HF) metals build one of the most exciting compound families that host the highest T_c among HFs, and thus, in terms of the energy scales, are close to high-T_c SC. The authors have married micro-structuring capabilities with plastic DACs and pulsed magnetic fields to explore field induced electronic nematicity and pressure induced unconventional superconductivity and how, within B-P-T phase space, they may be related as both exist in the vicinity of the quantum-critical suppression of the AFM order.

Report Number: 30

Fermi surface and Berry phase in CaFeAsF, a variant of the 1111 parent compounds

Terashima, T.; Hirose, H.T.; Uji, S. (NIMS); Graf, D. (National MagLab); Ma, Y.; Mu, G.; Hu, T. (Shanghai Institute of Microsystem and Information Technology); Suzuki, K.; Ikeda, H. (Ritsumeikan Univ.)
Published in: T. Terachima et al., Phys. Rev. X 8, 011014 (2018).

Here, the authors determine the Fermi surface of CaFeAsF in its antiferromagnetic state by performing quantum oscillation measurements and band-structure calculations. They find that the determined Fermi surface consists of a symmetry-related pair of Dirac electron cylinders and a normal hole-like cylinder. From analysis of the phase of the quantum-oscillation, they demonstrate that the electron cylinders carry a nontrivial Berry phase of π as expected for Dirac fermions. They also observe a nearly linear-in-field magnetoresistivity and an anomalous resistivity increase above about 30 T for fields along the inter-planar direction, likely related to the quantum limit of the electron orbit.

Report Number: 246

Spin susceptibility of charge ordered YBa₂Cu₃O_y across the upper critical field

Zhou, R., Hirata, M., Wu, T., Vinograd, I., Mayaffre, H., Krämer, S., Julien, M.-H.; Reyes, A.P., Kuhns, P.L.; Hardy, W.N., Liang, R., Bonn, D.A.
Published in: PNAS, 114, 13148–13153 (2017)

Although extensively studied, the value of the upper critical field (H_c2) in underdoped copper-oxide high-temperature superconductors has been controversial. By using NMR, a local probe, Zhou et al. find that their results support the picture in which H_c2 coincides with the melting transition of the vortex lattice, and H_c2 is suppressed by the charge order present already in zero field. However, the pseudogap seems to persist in the high-field normal state. This study provides a new perspective on several fundamental questions in cuprate research, but if the past is any guide, this may not be the last word on this topic!

Report Number: 446

Quantum fluctuations in cuprates near critical doping are co-planar with CuO plane

Shekhter, A. (DC National MagLab, Tallahassee FL); Ramshaw, B.J., (Cornell University, Ithaca, NY); Modic, K. (MaxPlanck-Institute for Chemical Physics of Solids, Dresden, Germany); Komiya, S., Ono, S., (Central Research Institute of Electric Power Industry, Nagasaka, Japan), Winter, L., Wieckert, F., Balakirev, F.F., Betts, J.B., McDonald R.D. (Los Alamos National Laboratory, Los Alamos National MagLab); Lian, X., Boebinger, G.S. (DC National MagLab, Tallahassee FL)
Published in: Giraldo-Gallo et al., Science 361, 479–481 (2018) and Shekhter et al., Manuscript in preparation

Following Shekhter et al’s discovery of "Scale invariance at the heart of a high temperature superconductivity”, published in Science earlier this year, the team has gone on to investigate the the role of magnetic field orientation. This work uses resistance measurements of the cuprate superconductor La_2-xSr_xCu0₄ in the highest available magnetic fields to explore the anomalous metallic state associated with the highest superconducting transition temperatures. In contrast to the magnetoresistance of conventional Fermi-liquids, controlled by the electron-dynamics at the Fermi-energy-scale, the magnetoresistance of these quantum-critical-metals is strikingly linear, only depending upon the energy scale of the component of field applied perpendicular to the copper-oxide planes - revealing a two dimensional soup of quantum fluctuations.

Report Number: 122

Design, Construction and First Testing of a 41.5 T All-Resistive Magnet

Toth, J. and Bole, S.
Published in: J. Toth and S. Bole, “Design, Construction and First Testing of a 41.5 T All-Resistive Magnet at the National MagLab in Tallahassee”, IEEE Trans. On Appl. Supercond., vol. 28, no. 3, April 2018, doi 10.1109/TASC.2017.2775578.

The proliferation of National MagLab Florida-Bitter designs has allowed magnet labs in Europe and Asia to develop record-high continuous field resistive magnets. Here the world record is strongly reestablished at the National MagLab with the successful testing of the 41.5 T all resistive magnet.

Report Number: 399

The 32 T Superconducting Magnet Achieves Full Field

Weijers, H.W., Markiewicz, W.D., Gavrilin, A.V., Voran, A.J., Viouchkov, Y.L., Gundlach, S.R., Noyes, P.D., Painter, T.A., Lu, J., Abraimov, D.V., Hannahs, S.T., Murphy, T.P., Stiers, E., Reyes, A.P.
Published in: Weijers, H.W., et al., IEEE Transactions on Applied Superconductivity, 24-3 4301805 (2015).

This report describes a significant achievement in magnet technology by attaining 32 T in a purely superconducting magnet system. This marks a large breakthrough in the application of REBCO conductors in high field magnets, surpassing a previous record of 24.5 T. It also makes available a magnet system with improved field quality and stability for users of the National MagLab DC Field Facility.

Report Number: 193

Post Quench Behavior of a Metallic Cladding (MC) No-Insulation (NI) Coil

Kim, K., Hu, X., Kim, K., Bhattarai, K.R., Radcliff, K. and Hahn, S. (ASC, National MagLab)
Published in: Kim, Kwanglok, Kwangmin Kim, Kabindra R. Bhattarai, Kyle Radcliff, Jae Young Jang, Young Jin Hwang, SangGap Lee, Sangwon Yoon, and Seungyong Hahn. "Quench behavior of a no-insulation coil wound with stainless steel cladding REBCO tape at 4.2 K." Superconductor Science and Technology 30, no. 7 (2017): 075001.

This research describes impressive R&D magnets that clearly demonstrate that the NI method can be used to achieve field approaching 20 T in a user-magnet configuration. It also outlines how challenging high-field magnet development is, and how many activities, from the HTS strand R&D characterization to magnet design & engineering and to instrumentation and protection, are integrated at the MagLab.

Report Number: 207

Development of Quench Protection of Bi-2212 Test Solenoid

Davis, D.S. (ASC, National MagLab, FSU, Physics); Trociewitz, U.P. (ASC, National MagLab); Gillman, J. (ASC, National MagLab); Miller, G. (ASC/MS&T, National MagLab)

Highlight describes the development of a quench protection system for future magnet systems that could reach above 1 GHz for NMR.

Report Number: 53

Evidence for Different Dopant Site Behavior by EXAFS in High Critical Current Nb₃Sn Superconductor Wires

Tarantini, C. (ASC-National MagLab); Heald S.M. (Argonne Nat. Lab.); Lee, P.J.; Brown, M.; Sung, Z.H. and Larbalestier, D.C. (ASC-National MagLab); Ghosh, A.K. (formerly Brookhaven Nat. Lab.)
Published in: Heald, Steve M., et al. "Evidence from EXAFS for Different Ta/Ti Site Occupancy in High Critical Current Density Nb 3 Sn Superconductor Wires." Scientific reports 8.1 (2018): 4798.

Study explains why, after a long time of study by the community, different dopants added to Nb₃Sn produce different reaction rates and response for improving the upper critical field. Results will have impact on next-generation conductors for very high field magnets, including NMR and hybrid outserts.

Report Number: 241

Significantly Improved Critical Current Density in Recent Bi-2212 Round Wire

Jiang, J., Bradford, G., Kametani, F., Trociewitz, U.P., Hellstrom, E.E., and Larbalestier, D.C. (National MagLab, FSU)
Published in: Jiang, J., et al., IEEE Transactions on Applied Superconductivity, 27 (4), 6400104 (2017).

Critical current of Bi-2212 has been raised by another factor of 2, a huge leap! The implication is that all-Bi-2212 coils are possible for high fields, without needing niobium-based outserts.

Report Number: 154

Transformation of Doped Graphite into Cluster-Encapsulated Fullerene Cages

Mulet-Gas, M. (MagLab, FSU); Abella, L. (Univ. Rovira I Virgili); Ceron, M.R., Castro, E. (Univ. Texas El Paso); Marshall, A.G. (MagLab, FSU); Rodriguez-Fortea, A. (Univ. Rovira I Virgili); Echegoyen, L. (Univ. Texas El Paso); Poblet, J.M. (Univ. Rovira I Virgili) and Dunk, P.W. (MagLab, FSU)
Published in: Nature Communications, 8, 1222 (2017).

Interesting manuscript. The clusterfullerene, M₃N@I_h-C₈₀, is formed by direct laser vaporization of metal- and nitrogen-doped graphite. The complex nanocarbon products are analyzed by FT-ICR mass spectrometry. This work discloses intrinsic chemical processes that are a fundamental property of carbon under the ‘harsh’ conditions typical of synthesis and will help tackle the challenge of nanocarbon structure formation for unique caged and hybrid carbon materials. Moreover, this work may be used as a benchmark to guide future nanocarbon explorations.

Report Number: 80

New Insights into Li-Ion Transport in Composite Electrolytes

Zheng, J. (FSU, Chemistry & Biochemistry); Feng, Z. (Oregon State U., Chemical, Biological & Environmental Engineering); Chan, C. (Arizona State U., Materials Science & Engineering); Hu, Y.-Y. (FSU, Chemistry & Biochemistry, National MagLab) and Huang, K. (U. of South Carolina, Engineering & Computing)
Published in: J. Mater. Chem. A, 5, 18457–18463 (2017) and Angew. Chem. Int. Ed., 55, 12538-12542 (2016).

Solid-electrolytes have a number of practical advantages over liquid electrolytes in Li-ion batteries. The groups of Y. Hu (FSU/National MagLab) and K. Huang (U of South Carolina) applied ⁶Li→⁷Li tracer-exchange NMR to investigate Li-ion transport in solid ceramic-polymer composite electrolytes. They used ⁶Li-enriched Li metal as the electrodes then monitored the increases of ⁶Li NMR signals of various sites inside the solid electrolytes from the exchange with the enriched 6Li metal electrodes (the natural ⁶Li abundance is only 7.4%). The ⁶Li→⁷Li tracer-exchange NMR allows them to get detailed information about pathways of Li-ion transport.

Report Number: 88

Probing Molecular Magnetism by Infrared & Raman Spectroscopies in Magnetic Fields

Xue, Z.L., Moseley, D.H., Mings, C.M. (U. Tennessee, Chemistry); Thirunavukkuarasu, K. (FAMU, Physics); Lu, Z., Smirnov, D. (National MagLab); Liu, Z., Stavretis, S.E. (U. Tennessee, Chemistry)
Published in: Nat. Comm. (2018) accepted

Spin-phonon coupling plays a critical role in properties of single-molecule magnets (SMMs), but is not well understood. The authors have observed for the first time spinphonon couplings in cobalt SMMs by magneto-Raman and far-infrared spectroscopies. This work helps explain the origin of the spinhonon entanglement in transition metal compounds.

Report Number: 105

Ratiometric pH Imaging with a Co^II₂ MRI Probe via CEST Effects of Opposing pH Dependences

Thorarinsdottir, A.E., Du, K. (Northwestern U., Chemistry); Collins, J.H.P. (NHMFL); Harris, T.D. (Northwestern U., Chemistry).
Published in: J. Am. Chem. Soc. 139/44/15836-15847

Intracellular acidification is a hallmark of tissue pathophysiology and is typically measured using 31P NMR which has limited spatial resolution due to the low gamma nucleus. An exciting alternative is to develop a 1H based approach capable of high resolution imaging. In order to achieve this, researchers from Northwestern in collaboration with MagLab scientist in AMRIS developed a dinuclear Co^II complexes featuring two types of that exhibit exhibited chemical exchange transfer at different chemical shifts with opposing pH dependences. One of the tested compounds revealed highly pH-dependent CEST peak intensities in the pH range 6.5–7.6. The ratios of CEST intensities at 104 and 64 ppm vs H₂O could be used to construct a linear calibration curve of log₁₀(CEST_{104 ppm}/CEST_{64 ppm}) vs pH, providing a pH sensitivity of 0.99(7) per pH unit, which was reported to be over 2-fold greater than that previously reported for related probes.

Report Number: 365

Advanced Chemical Characterization of Pyrolysis Bio-Oils from Landfill Waste, Recycled Plastics, and Pine Forest Residue

Ware, R.L. (FSU, Chemistry); Rowland, S.M. (National MagLab, ICR); Rodgers, R.P. (National MagLab, ICR) and Marshall, A.G. FSU, Chemistry; National MagLab, ICR), Fleming, H. (HK Petroleum)
Published in: Energy & Fuels 31/8210-8216

The work links the economic value of pyrolysis oils generated from waste forestry residue, recycled plastics, and landfill waste to their molecular composition. Many analytical techniques were employed, and the data combined for a comprehensive molecular-level explanation of the pyrolysis products, and their link to the starting material.

Report Number: 366

Organic Coating on Biochar Explains Its Nutrient Retention and Stimulation of Soil Fertility

Hagemman, N. (Univ. Tuebingen, Germany); Joseph, S. (Univ. Newcastle, Australia); Schmidt, H.-P. (Ithaka Inst. Carbon Strategies, Switzerland); Kammann, C.I. (Hochschule Geisenheim Univ., Germany); Harter, J. (Univ. Tuebingen, Germany); Borch, T., Young, R.B. (Colorado State University); Varga, K. (University of New Hampshire); Taherymoosavi, S. (University of Newcastle); Elliott, K.W. (University of New Hampshire); McKenna, A.M. (National MagLab, ICR); Albu, M., Mayrhofer, C. (Austrian Cooperative Research, Centre for Electron Microscopy and Nanoanalysis); Obst, M. (University of Bayreuth, Germany); Conte,P. (Università degli Studi di Palermo, Italy); Dieguez-Alonso, A. (Technische Universität Berlin, Germany); Orsetti, S., Subdiaga, E. (University of Tuebingen, Germany); Behrens, S. (University of Minnesota) and Kappler, A. (University of Tuebingen, Germany)
Published in: Nature Comm. 8(1089), 1-11 (2017).

When biochar is used as a soil amendment, it was thought that surface oxidation was responsible for increased nutrient retention. However, the authors identify a complex, nutrient-rich organic coating on co-composted biochar that covers the outer and inner (pore) surfaces of biochar particles by high-resolution spectro (micro)scopy and FT-ICR mass spectrometry. This implies that the functioning of biochar in soil is determined by the formation of an organic coating, rather than biochar surface oxidation, as previously suggested, and this coating is enriched in nitrogen-containing organics.

Report Number: 275

Advances in Asphaltene Petroleomics. Part 1: Asphaltenes Are Composed of Abundant Island and Archipelago Structural Motifs

Chacón-Patiño, M.L. (National MagLab); Rowland, S.M. (National MagLab, Future Fuels Institute); Rodgers, R.P. (National MagLab, Future Fuels Institute)
Published in: Energy & Fuels, 31, 12, 13509-13518 (2017)

The debate over asphaltene structure remains one of the most hotly debated topics in heavy oil characterization. Here, authors report a fractionation technique that yields structurally-dependent fractions (island and archipelago) that are further characterized by ultrahigh resolution FT-ICR mass spectrometry, and overcomes ionization matrix effects that have limited asphaltene molecular characterization to a subset of compounds for years.

Report Number: 39

Identification and Characterization of Human Proteoforms by Top-Down LC-21 Tesla FT-ICR Mass Spectrometry

Anderson, L.C. (National MagLab); DeHart, C.J. (National MagLab/NU); Kaiser, N.K. (National MagLab); Fellers, R.T. (NU); Smith, D.F. (National MagLab); Greer, J.B. (NU); LeDuc, R.D. (NU) ; Blakney, G.T. (National MagLab); Thomas, P.M. (NU); Kelleher, N.L. (NU); Hendrickson, C.L (National MagLab)
Published in: J. Proteome Res., 16, 1087-1096

High-throughput characterization of intact proteins from biological samples (top-down proteomics) by mass spectrometry requires instrumentation that achieves high mass resolving power, mass accuracy, sensitivity, and spectral acquisition rate only achievable at 21 tesla. Often, hundreds of experiments are necessary to obtain sufficient coverage of the targeted proteome. Here, authors demonstrate top-down proteomic analysis on human colorectal cancer cell lysate, and produce unparalleled number of identified proteins per injection compared to previous studies.

Report Number: 209

Gramicidin Ion Binding and Conductance: New Insights from ¹⁷O Solid State NMR at 35T SCH Magnet

Paulino, J., Hung, I. and Gan, Z. (National MagLab); Cross, T.A. (FSU, Chemistry & Biochemistry, National MagLab) and Chekmenev, E. (Vanderbilt U., Ingram Cancer Center)
Published in: J. Am. Chem. Soc. 2017, 139, 17953−17963

Oxygen is among one of most important elements in chemistry, biology and material sciences. The potential of ¹⁷O NMR for obtaining detailed structural, dynamic and functional information has not been fully realized due to its low gyromagnetic ratio, low natural isotopic abundance (0.037%) and large quadrupolar broadening. The group of R. Griffin at MIT has developed a new ¹⁷O enrichment strategy for bio-molecules and utilized high magnetic fields including the newly commissioned 36T Series-Connected-Hybrid (SCH) magnet at the National MagLab for obtaining 17O NMR correlation spectra and distance information with nearby nuclei. Their work will unleash the potential of applying ¹⁷O NMR for biological solids which just starts being exploited.

Report Number: 291

Ultrahigh Field ¹⁷O Magic-Angle Spinning NMR Using Series-Connected-Hybrid Magnet

Keeler, E.G. (MIT, Chemistry); Michaelis, V.K. (U. of Alberta, Chemistry); Colvin, M.T. and Griffin, R.G. (MIT, Chemistry); Hung, I. and Gorkov, P.L. (National MagLab); Cross, T.A. (FSU, Chemistry & Biochemistry, National MagLab) and Gan, Z. (National MagLab)
Published in: J. Am. Chem. Soc.

Granicidin A (gA) forms a dimeric ion channel with a bore lined by peptide's carbonyl oxygens. The groups of T. Cross at FSU/National MagLab and E. Chekmenev at Vanderbilt have previously used ¹⁷O NMR up to 900MHz field of mechanically aligned gA to study channel-cation interactions. Their recent ¹⁷O results obtained from the 36T Series-Connected-Hybrid (SCH) magnet reveals splitting of ¹⁷O resonance which vary among peptide positions. They attributes the splitting from the symmetry breaking due to the hydrogen bonding to a chain of water molecules inside the channel. Their finding was made possible for the first time by the high field of SCH which improves the spectral resolution and sensitivity of quadrupolar nuclei in general. In addition, the high magnetic field helps the uniformity of alignment from magnetic susceptibility further narrowing the ¹⁷O lines of the aligned gA samples.

Report Number: 307

Across the Tree of Life: Radiation Resistance Gauged by High-Field EPR

Sharma, A., Hoffman, B.M. (Northwestern U., Chemistry) and Ozarowski, A. (National MagLab)
Published in: Across the tree of life, radiation resistance is governed by antioxidant Mn²⁺, gauged by paramagnetic resonance, Sharma, A.; Gaidamakova, E.K.; Grichenko, O.; Matrosova, V. Y.; Hoeke, V.; Klimenkova, P.; Conze, I.H.; Volpe, R.P.; Tkavc, R.; Gostinˇcar, C.; Gunde-Cimerman, N.; DiRuggiero, J.; Shuryak, I.; Ozarowski, A.; Hoffman, B.M. and Daly, M.J. P. Natl. Acad. Sci. U.S.A., 114, 44, E9253-E9260 (2017)

Evidence is mounting that small high-symmetry antioxidant complexes of manganous ions with metabolites (H-Mn²⁺) are responsible for cellular resistance to gamma rays. This study shows that the amount of H-Mn²⁺ in non-irradiated living cells can be readily gauged by electron paramagnetic resonance (EPR) spectroscopy and is highly diagnostic of DNA repair efficiency and survival after gamma radiation exposure.

Report Number: 368

Accurate Identification of Unknown and Known Metabolic Mixture Components by Combining 3D NMR with FT-ICR MS/M

Wang, C. (Ohio State U., Chemistry); He, L. (FSU, Chemistry); Li, D. and Brüschweiler-Li, L. (Ohio State U., Campus Chemical Instrument Center); Marshall, A.G. (FSU, Chemistry; National MagLab, ICR) and Brüschweiler, R. (Ohio State U., Chemistry)
Published in: Proteome Res.16/10/3774-3786

Scientist at Ohio State University utilized National MagLab 9.4 T Fourier transform ion cyclotron resonance mass spectrometer, in order to expand upon on their ground-breaking technique development which allows for the combined analysis of complex mixtures using individual strengths of mass spec and NMR. In this report the authors present a generalized solution (called SUMMIT) for the untargeted identification of both known and unknown metabolites by combining ultrahigh-resolution Fourier transform ion cyclotron resonance mass to assign unique elemental compositions with 3D NMR complemented by 2D NMR experiments as the primary source of information for spin-system identification and validation by tandem MS. This general approach was demonstrated using model mixtures and an E. coli cell lysate. For 19 of the 25 model metabolites SUMMIT yielded complete structures that matched those in the mixture independent of database information. For E. coli, SUMMIT identified 20 previously known metabolites with 3 or more 1H spins independent of database information. By providing structural information for entire metabolites or molecular fragments, SUMMIT MS/NMR greatly assists the targeted or untargeted analysis of complex mixtures of unknown compounds.