TY - JOUR AB - The quantum anomalous Hall (QAH) effect combines topology and magnetism to produce precisely quantized Hall resistance at zero magnetic field. We report the observation of a QAH effect in twisted bilayer graphene aligned to hexagonal boron nitride. The effect is driven by intrinsic strong interactions, which polarize the electrons into a single spin- and valley-resolved moiré miniband with Chern number C = 1. In contrast to magnetically doped systems, the measured transport energy gap is larger than the Curie temperature for magnetic ordering, and quantization to within 0.1% of the von Klitzing constant persists to temperatures of several kelvin at zero magnetic field. Electrical currents as small as 1 nanoampere controllably switch the magnetic order between states of opposite polarization, forming an electrically rewritable magnetic memory. AU - Serlin, M. AU - Tschirhart, C. L. AU - Polshyn, Hryhoriy AU - Zhang, Y. AU - Zhu, J. AU - Watanabe, K. AU - Taniguchi, T. AU - Balents, L. AU - Young, A. F. ID - 10619 IS - 6480 JF - Science KW - multidisciplinary SN - 0036-8075 TI - Intrinsic quantized anomalous Hall effect in a moiré heterostructure VL - 367 ER - TY - CONF AB - Twisted bilayer graphene (tBLG) near the flat band condition is a versatile new platform for the study of correlated physics in 2D. Resistive states have been observed at several commensurate fillings of the flat miniband, along with superconducting states near half filling. To better understand the electronic structure of this system, we study electronic transport of graphite gated superconducting tBLG devices in the normal regime. At high magnetic fields, we observe full lifting of the spin and valley degeneracy. The transitions in the splitting of this four-fold degeneracy as a function of carrier density indicate Landau level (LL) crossings, which tilted field measurements show occur between LLs with different valley polarization. Similar LL structure measured in two devices, one with twist angle θ=1.08° at ambient pressure and one at θ=1.27° and 1.33GPa, suggests that the dimensionless combination of twist angle and interlayer coupling controls the relevant details of the band structure. In addition, we find that the temperature dependence of the resistance at B=0 shows linear growth at several hundred Ohm/K in a broad range of temperatures. We discuss the implications for modeling the scattering processes in this system. AU - Polshyn, Hryhoriy AU - Zhang, Yuxuan AU - Yankowitz, Matthew AU - Chen, Shaowen AU - Taniguchi, Takashi AU - Watanabe, Kenji AU - Graf, David E. AU - Dean, Cory R. AU - Young, Andrea ID - 10724 IS - 2 SN - 0003-0503 T2 - APS March Meeting 2019 TI - Normal state transport in superconducting twisted bilayer graphene VL - 64 ER - TY - CONF AB - Bilayer graphene, rotationally faulted to ~1.1 degree misalignment, has recently been shown to host superconducting and resistive states associated with the formation of a flat electronic band. While numerous theories exist for the origins of both states, direct validation of these theories remains an outstanding experimental problem. Here, we focus on the resistive states occurring at commensurate filling (1/2, 1/4, and 3/4) of the two lowest superlattice bands. We test theoretical proposals that these states arise due to broken spin—and/or valley—symmetry by performing direct magnetic imaging with nanoscale SQUID-on-tip microscopy. This technique provides single-spin resolved magnetometry on sub-100nm length scales. I will present imaging data from our 4.2K nSOT microscope on graphite-gated twisted bilayers near the flat band condition and discuss the implications for the physics of the commensurate resistive states. AU - Serlin, Marec AU - Tschirhart, Charles AU - Polshyn, Hryhoriy AU - Zhu, Jiacheng AU - Huber, Martin E. AU - Young, Andrea ID - 10722 IS - 2 SN - 0003-0503 T2 - APS March Meeting 2019 TI - Direct Imaging of magnetic structure in twisted bilayer graphene with scanning nanoSQUID-On-Tip microscopy VL - 64 ER - TY - CONF AB - Bilayer graphene with ~ 1.1 degrees twist mismatch between the layers hosts a low energy flat band in which the Coulomb interaction is large relative to the bandwidth, promoting correlated insulating states at half band filling, and superconducting (SC) phases with dome-like structure neighboring correlated insulating states. Here we show measurements of a dual-graphite-gated twisted bilayer graphene device, which minimizes charge inhomogeneity. We observe new correlated phases, including for the first time a SC pocket near half-filling of the electron-doped band and resistive states at quarter-filling of both bands that emerge in a magnetic field. Changing the layer polarization with vertical electric field reveals an unexpected competition between SC and correlated insulator phases, which we interpret to result from differences in disorder of each graphene layer and underscores the spatial inhomogeneity like twist angle as a significant source of disorder in these devices [1]. AU - Chen, Shaowen AU - Yankowitz, Matthew AU - Polshyn, Hryhoriy AU - Watanabe, Kenji AU - Taniguchi, Takashi AU - Graf, David E. AU - Young, Andrea AU - Dean, Cory R. ID - 10725 IS - 2 SN - 0003-0503 T2 - APS March Meeting 2019 TI - Correlated insulating and superconducting phases in twisted bilayer graphene VL - 64 ER - TY - CONF AB - In monolayer graphene, the interplay of electronic correlations with the internal spin- and valley- degrees of freedom leads to a complex phase diagram of isospin symmetry breaking at high magnetic fields. Recently, Wei et al. (Science (2018)) demonstrated that spin waves can be electrically generated and detected in graphene heterojunctions, allowing direct experiment access to the spin degree of freedom. Here, we apply this technique to high quality graphite-gated graphene devices showing robust fractional quantum Hall phases and isospin phase transitions. We use an edgeless Corbino geometry to eliminate the contributions of edge states to the spin-wave mediated nonlocal voltage, allowing unambiguous identification of spin wave transport signatures. Our data reveal two phases within the ν = 1 plateau. For exactly ν=1, charge is localized but spin waves propagate freely while small carrier doping completely quenches the low-energy spin-wave transport, even as those charges remain localized. We identify this new phase as a spin textured electron solid. We also find that spin-wave transport is modulated by phase transitions in the valley order that preserve spin polarization, suggesting that this technique is sensitive to both spin and valley order. AU - Zhou, Haoxin AU - Polshyn, Hryhoriy AU - Tanaguchi, Takashi AU - Watanabe, Kenji AU - Young, Andrea ID - 10723 IS - 2 SN - 0003-0503 T2 - APS March Meeting 2019 TI - Spin wave transport through electron solids and fractional quantum Hall liquids in graphene VL - 64 ER - TY - CONF AB - This report presents the results of a friendly competition for formal verification of continuous and hybrid systems with piecewise constant dynamics. The friendly competition took place as part of the workshop Applied Verification for Continuous and Hybrid Systems (ARCH) in 2019. In this third edition, six tools have been applied to solve five different benchmark problems in the category for piecewise constant dynamics: BACH, Lyse, Hy- COMP, PHAVer/SX, PHAVerLite, and VeriSiMPL. Compared to last year, a new tool has participated (HyCOMP) and PHAVerLite has replaced PHAVer-lite. The result is a snap- shot of the current landscape of tools and the types of benchmarks they are particularly suited for. Due to the diversity of problems, we are not ranking tools, yet the presented results probably provide the most complete assessment of tools for the safety verification of continuous and hybrid systems with piecewise constant dynamics up to this date. AU - Frehse, Goran AU - Abate, Alessandro AU - Adzkiya, Dieky AU - Becchi, Anna AU - Bu, Lei AU - Cimatti, Alessandro AU - Giacobbe, Mirco AU - Griggio, Alberto AU - Mover, Sergio AU - Mufid, Muhammad Syifa'ul AU - Riouak, Idriss AU - Tonetta, Stefano AU - Zaffanella, Enea ED - Frehse, Goran ED - Althoff, Matthias ID - 10877 SN - 2398-7340 T2 - ARCH19. 6th International Workshop on Applied Verification of Continuous and Hybrid Systems TI - ARCH-COMP19 Category Report: Hybrid systems with piecewise constant dynamics VL - 61 ER - TY - JOUR AB - Many adult tissues contain postmitotic cells as old as the host organism. The only organelle that does not turn over in these cells is the nucleus, and its maintenance represents a formidable challenge, as it harbors regulatory proteins that persist throughout adulthood. Here we developed strategies to visualize two classes of such long-lived proteins, histones and nucleoporins, to understand the function of protein longevity in nuclear maintenance. Genome-wide mapping of histones revealed specific enrichment of long-lived variants at silent gene loci. Interestingly, nuclear pores are maintained by piecemeal replacement of subunits, resulting in mosaic complexes composed of polypeptides with vastly different ages. In contrast, nondividing quiescent cells remove old nuclear pores in an ESCRT-dependent manner. Our findings reveal distinct molecular strategies of nuclear maintenance, linking lifelong protein persistence to gene regulation and nuclear integrity. AU - Toyama, Brandon H. AU - Arrojo e Drigo, Rafael AU - Lev-Ram, Varda AU - Ramachandra, Ranjan AU - Deerinck, Thomas J. AU - Lechene, Claude AU - Ellisman, Mark H. AU - HETZER, Martin W ID - 11061 IS - 2 JF - Journal of Cell Biology KW - Cell Biology SN - 0021-9525 TI - Visualization of long-lived proteins reveals age mosaicism within nuclei of postmitotic cells VL - 218 ER - TY - JOUR AB - Most neurons are not replaced during an animal’s lifetime. This nondividing state is characterized by extreme longevity and age-dependent decline of key regulatory proteins. To study the lifespans of cells and proteins in adult tissues, we combined isotope labeling of mice with a hybrid imaging method (MIMS-EM). Using 15N mapping, we show that liver and pancreas are composed of cells with vastly different ages, many as old as the animal. Strikingly, we also found that a subset of fibroblasts and endothelial cells, both known for their replicative potential, are characterized by the absence of cell division during adulthood. In addition, we show that the primary cilia of beta cells and neurons contains different structural regions with vastly different lifespans. Based on these results, we propose that age mosaicism across multiple scales is a fundamental principle of adult tissue, cell, and protein complex organization. AU - Arrojo e Drigo, Rafael AU - Lev-Ram, Varda AU - Tyagi, Swati AU - Ramachandra, Ranjan AU - Deerinck, Thomas AU - Bushong, Eric AU - Phan, Sebastien AU - Orphan, Victoria AU - Lechene, Claude AU - Ellisman, Mark H. AU - HETZER, Martin W ID - 11062 IS - 2 JF - Cell Metabolism KW - Cell Biology KW - Molecular Biology KW - Physiology SN - 1550-4131 TI - Age mosaicism across multiple scales in adult tissues VL - 30 ER - TY - JOUR AB - Deep optical spectroscopic surveys of galaxies provide a unique opportunity to investigate rest-frame ultra-violet (UV) emission line properties of galaxies at z ∼ 2 − 4.5. Here we combine VLT/MUSE Guaranteed Time Observations of the Hubble Deep Field South, Ultra Deep Field, COSMOS, and several quasar fields with other publicly available data from VLT/VIMOS and VLT/FORS2 to construct a catalogue of He II λ1640 emitters at z ≳ 2. The deepest areas of our MUSE pointings reach a 3σ line flux limit of 3.1 × 10−19 erg s−1 cm−2. After discarding broad-line active galactic nuclei, we find 13 He II λ1640 detections from MUSE with a median MUV = −20.1 and 21 tentative He II λ1640 detections from other public surveys. Excluding Lyα, all except two galaxies in our sample show at least one other rest-UV emission line, with C III] λ1907, λ1909 being the most prominent. We use multi-wavelength data available in the Hubble legacy fields to derive basic galaxy properties of our sample through spectral energy distribution fitting techniques. Taking advantage of the high-quality spectra obtained by MUSE (∼10 − 30 h of exposure time per pointing), we use photo-ionisation models to study the rest-UV emission line diagnostics of the He II λ1640 emitters. Line ratios of our sample can be reproduced by moderately sub-solar photo-ionisation models, however, we find that including effects of binary stars lead to degeneracies in most free parameters. Even after considering extra ionising photons produced by extreme sub-solar metallicity binary stellar models, photo-ionisation models are unable to reproduce rest-frame He II λ1640 equivalent widths (∼0.2 − 10 Å), thus additional mechanisms are necessary in models to match the observed He II λ1640 properties. AU - Nanayakkara, Themiya AU - Brinchmann, Jarle AU - Boogaard, Leindert AU - Bouwens, Rychard AU - Cantalupo, Sebastiano AU - Feltre, Anna AU - Kollatschny, Wolfram AU - Marino, Raffaella Anna AU - Maseda, Michael AU - Matthee, Jorryt J AU - Paalvast, Mieke AU - Richard, Johan AU - Verhamme, Anne ID - 11499 JF - Astronomy & Astrophysics KW - Space and Planetary Science KW - Astronomy and Astrophysics KW - galaxies: ISM / galaxies: star formation / galaxies: evolution / galaxies: high-redshift SN - 0004-6361 TI - Exploring He II λ1640 emission line properties at z ∼2−4 VL - 648 ER - TY - JOUR AB - Contact. This paper presents the results obtained with the Multi-Unit Spectroscopic Explorer (MUSE) at the ESO Very Large Telescope on the faint end of the Lyman-alpha luminosity function (LF) based on deep observations of four lensing clusters. The goal of our project is to set strong constraints on the relative contribution of the Lyman-alpha emitter (LAE) population to cosmic reionization. Aims. The precise aim of the present study is to further constrain the abundance of LAEs by taking advantage of the magnification provided by lensing clusters to build a blindly selected sample of galaxies which is less biased than current blank field samples in redshift and luminosity. By construction, this sample of LAEs is complementary to those built from deep blank fields, whether observed by MUSE or by other facilities, and makes it possible to determine the shape of the LF at fainter levels, as well as its evolution with redshift. Methods. We selected a sample of 156 LAEs with redshifts between 2.9 ≤ z ≤ 6.7 and magnification-corrected luminosities in the range 39 ≲ log LLyα [erg s−1] ≲43. To properly take into account the individual differences in detection conditions between the LAEs when computing the LF, including lensing configurations, and spatial and spectral morphologies, the non-parametric 1/Vmax method was adopted. The price to pay to benefit from magnification is a reduction of the effective volume of the survey, together with a more complex analysis procedure to properly determine the effective volume Vmax for each galaxy. In this paper we present a complete procedure for the determination of the LF based on IFU detections in lensing clusters. This procedure, including some new methods for masking, effective volume integration and (individual) completeness determinations, has been fully automated when possible, and it can be easily generalized to the analysis of IFU observations in blank fields. Results. As a result of this analysis, the Lyman-alpha LF has been obtained in four different redshift bins: 2.9 <  z <  6, 7, 2.9 <  z <  4.0, 4.0 <  z <  5.0, and 5.0 <  z <  6.7 with constraints down to log LLyα = 40.5. From our data only, no significant evolution of LF mean slope can be found. When performing a Schechter analysis also including data from the literature to complete the present sample towards the brightest luminosities, a steep faint end slope was measured varying from α = −1.69−0.08+0.08 to α = −1.87−0.12+0.12 between the lowest and the highest redshift bins. Conclusions. The contribution of the LAE population to the star formation rate density at z ∼ 6 is ≲50% depending on the luminosity limit considered, which is of the same order as the Lyman-break galaxy (LBG) contribution. The evolution of the LAE contribution with redshift depends on the assumed escape fraction of Lyman-alpha photons, and appears to slightly increase with increasing redshift when this fraction is conservatively set to one. Depending on the intersection between the LAE/LBG populations, the contribution of the observed galaxies to the ionizing flux may suffice to keep the universe ionized at z ∼ 6. AU - de La Vieuville, G. AU - Bina, D. AU - Pello, R. AU - Mahler, G. AU - Richard, J. AU - Drake, A. B. AU - Herenz, E. C. AU - Bauer, F. E. AU - Clément, B. AU - Lagattuta, D. AU - Laporte, N. AU - Martinez, J. AU - Patrício, V. AU - Wisotzki, L. AU - Zabl, J. AU - Bouwens, R. J. AU - Contini, T. AU - Garel, T. AU - Guiderdoni, B. AU - Marino, R. A. AU - Maseda, M. V. AU - Matthee, Jorryt J AU - Schaye, J. AU - Soucail, G. ID - 11505 JF - Astronomy & Astrophysics KW - Space and Planetary Science KW - Astronomy and Astrophysics KW - gravitational lensing: strong / galaxies: high-redshift / dark ages KW - reionization KW - first stars / galaxies: clusters: general / galaxies: luminosity function KW - mass function SN - 0004-6361 TI - Faint end of the z ∼ 3–7 luminosity function of Lyman-alpha emitters behind lensing clusters observed with MUSE VL - 628 ER -