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Tuning Insulator-Semimetal Transitions in 3D Topological Insulator thin Films by Intersurface Hybridization and In-Plane Magnetic Fields

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Physical Review Letters 2019年第20期123卷 207701-207701页

作者： Yang Xu Guodong Jiang Ireneusz Miotkowski Rudro R. Biswas Yong P. Chen Department of Physics and Astronomy Purdue University West Lafayette Indiana 47907 USA Birck Nanotechnology Center Purdue University West Lafayette Indiana 47907 USA Purdue Quantum Science and Engineering Institute Purdue University West Lafayette Indiana 47907 USA School of Electrical and Computer Engineering Purdue University West Lafayette Indiana 47907 USA WPI-AIMR International Research Center for Materials Sciences Tohoku University Sendai 980-8577 Japan

A pair of Dirac points (analogous to a vortex-antivortex pair) associated with opposite topological numbers (with ±π Berry phases) can be merged together through parameter tuning and annihilated to gap the Dirac spectrum, offering a canonical example of a topological phase transition. Here, we report transport studies on thin films of BiSbTeSe2, which is a 3D topological insulator that hosts spin-helical gapless (semimetallic) Dirac fermion surface states for sufficiently thick samples, with an observed resistivity close to h/4e2 at the charge neutral point. When the sample thickness is reduced to below ∼10 nm thick, we observe a transition from metallic to insulating behavior, consistent with the expectation that the Dirac cones from the top and bottom surfaces hybridize (analogous to a “merging” in the real space) to give a trivial gapped insulator. Furthermore, we observe that an in-plane magnetic field can drive the system again towards a metallic behavior, with a prominent negative magnetoresistance (up to ∼−95%) and a temperature-insensitive resistivity close to h/2e2 at the charge neutral point. The observation is consistent with a predicted effect of an in-plane magnetic field to reduce the hybridization gap (which, if small enough, may be smeared by disorder and give rise to a metallic behavior). A sufficiently strong magnetic field is predicted to restore and split again the Dirac points in the momentum space, inducing a distinct 2D topological semimetal phase with two single-fold Dirac cones of opposite spin-momentum windings.

关键词： electrical conductivity Electronic structure Magnetoresistance Magnetotransport Metal-insulator transition Surface states Topological insulators Topological phases of matter

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Linear and Nonlinear Reconstruction Algorithms for Atomic-Resolution Tomography Using Phase Contrast Electron Microscopy

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Microscopy and Microanalysis 2018年第S1期24卷 110-111页

作者： Colin Ophus David Ren Michael Chen Catherine Groschner Mary Scott Laura Waller Molecular Foundry Lawrence Berkeley National Laboratory Berkeley USA Department of Electrical Engineering and Computer Science UC Berkeley Berkeley CA Materials Science and Engineering UC Berkeley Berkeley CA

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Title: Observation of Bloch-Siegert Shift in an Atomically Thin Crystal

Title: Observation of Bloch-Siegert Shift in an Atomically T...

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2018 IEEE Photonics Society Summer Topicals Meeting Series, SUM 2018

作者： Sie, Edbert J. Lui, C.H. Lee, Yi-Hsien Fu, Liang Kong, Jing Gedik, Nuh Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Physics and Astronomy University of California RiversideCA92521 United States Materials Science and Engineering National Tsing-Hua University Hsinchu30013 Taiwan Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Geballe Laboratory for Advanced Materials Stanford University StanfordCA94305 United States

ISBN: (纸本)9781538653432

Coherent light-matter interaction can be used to manipulate the energy levels of atoms, molecules and solids. When light with frequency ω is detuned away from a resonance ω0, repulsion between the photon-dressed (Floquet) states can lead to a shift of energy resonance. The dominant effect is the optical Stark shift (∝ 1/( ω0-ω)), but there is an additional contribution from the so-called Bloch-Siegert shift (∝ 1/( ω0 + ω)). Although it is common in atoms and molecules, the observation of Bloch-Siegert shift in solids has so far been limited only to artificial atoms since the shifts were small (2 under infrared optical driving by virtue of the strong light-matter interaction in this system. Moreover, we can disentangle the Bloch-Siegert shift entirely from the optical Stark shift, because the two effects are found to obey opposite selection rules at different valleys. By controlling the light helicity, we can confine the Bloch-Siegert shift to occur only at one valley, and the optical Stark shift at the other valley. Such a valley-exclusive Bloch-Siegert shift allows for enhanced control over the valleytronic properties in two-dimensional materials, and offers a new avenue to explore quantum optics in solids. © 2018 IEEE.

关键词： Molecules

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Photoluminescence mapping and time-domain thermo-photoluminescence for rapid imaging and measurement of thermal conductivity of boron arsenide

arXiv

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arXiv 2019年

作者： Yue, Shuai Gamage, Geethal Amila Mohebinia, Mohammadjavad Mayerich, David Talari, Vishal Deng, Yu Tian, Fei Dai, Shen-Yu Sun, Haoran Hadjiev, Viktor G. Zhang, Wei Feng, Guoying Hu, Jonathan Liu, Dong Wang, Zhiming Ren, Zhifeng Bao, Jiming Institute of Fundamental and Frontier Sciences University of Electronic Science and Technology of China Chengdu Sichuan610054 China Department of Electronic and Computer Engineering University of Houston HoustonTX77204 United States Department of Physics Texas Center for Superconductivity University of Houston HoustonTX77204 United States Materials Science & Engineering University of Houston HoustonTX77204 United States Department of Mechanical Engineering University of Houston HoustonTX77204 United States College of Electronics & Information Engineering Sichuan University Chengdu Sichuan610064 China Texas Center for Superconductivity University of Houston HoustonTX77204 United States Department of Electrical and Computer Engineering Baylor University WacoTX76798 United States

Cubic boron arsenide (BAs) is attracting greater attention due to the recent experimental demonstration of ultrahigh thermal conductivity K above 1000 W/m·K. However, its bandgap has not been settled and a simple yet effective method to probe its crystal quality is missing. Furthermore, traditional K measurement methods are destructive and time consuming, thus they cannot meet the urgent demand for fast screening of high K materials. After we experimentally established 1.82 eV as the indirect bandgap of BAs and observed room-temperature band-edge photoluminescence, we developed two new optical techniques that can provide rapid and non-destructive characterization of K with little sample preparation: photoluminescence mapping (PL-mapping) and time-domain thermo-photoluminescence (TDTP). PL-mapping provides nearly real-time image of crystal quality and K over mm-sized crystal surfaces;while TDTP allows us to pick up any spot on the sample surface and measure its K using nanosecond laser pulses. These new techniques reveal that the apparent single crystals are not only non-uniform in K, but also are made of domains of very distinct K. Because PL-mapping and TDTP are based on the band-edge PL and its dependence on temperature, they can be applied to other semiconductors, thus paving the way for rapid identification and development of high-K semiconducting materials. Copyright © 2019, The Authors. All rights reserved.

关键词： Photoluminescence

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Organic Semiconductors: Fast‐Response, Highly Air‐Stable, and Water‐Resistant Organic Photodetectors Based on a Single‐Crystal Pt Complex (Adv. Mater. 2/2020)

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Advanced materials 2020年第2期32卷 2070015-2070015页

作者： Dharmaraj Periyanagounder Tzu‐Chiao Wei Ting‐You Li Chun‐Ho Lin Théo Piechota Gonçalves Hui‐Chun Fu Dung‐Sheng Tsai Jr‐Jian Ke Hung‐Wei Kuo Kuo‐Wei Huang Norman Lu Xiaosheng Fang Jr‐Hau He Computer Electrical and Mathematical Sciences and Engineering Division King Abdullah University of Science & Technology Thuwal 23955–6900 Saudi Arabia Department of Molecular Science and Engineering National Taipei University of Technology Taipei 106 Taiwan ROC KAUST Catalyst Centre Physical Science and Engineering Division King Abdullah University of Science & Technology Thuwal 23955–6900 Saudi Arabia Institute of Organic and Polymeric Materials National Taipei University of Technology Taipei 106 Taiwan ROC Department of Materials Science Fudan University Shanghai 200433 China Department of Materials Science and Engineering City University of Hong Kong Kowloon Hong Kong SAR 999077 China

The success of any organic device ultimately relies on two factors: mobility and stability under ambient and extreme conditions. Toward this goal, in article number 1904634, Norman Lu, Xiaosheng Fang, Jr‐Hau He, and co‐workers develop a Pt‐complex‐based organic semiconductor with high mobility and stability, as an active channel and/or photoabsorption layer for high‐performance organic device applications. The device displays the highest combined efficiency and stability reported to date for an organic semiconductor.

关键词： fluorine functionalization metal–ligand charge transfer organic photodetectors organic semiconductors transfer integrals

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arXiv

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arXiv 2019年

作者： Burg, G. William Zhu, Jihang Taniguchi, Takashi Watanabe, Kenji MacDonald, Allan H. Tutuc, Emanuel Microelectronics Research Center Department of Electrical and Computer Engineering University of Texas at Austin AustinTX78758 United States Department of Physics University of Texas at Austin AustinTX78712 United States National Institute of Materials Science 1-1 Namiki Tsukuba Ibaraki305-0044 Japan

We present a combined experimental and theoretical study of twisted double bilayer graphene with twist angles between 1° and 1.35°. Consistent with moiré band structure calculations, we observe insulators at integer moiré band fillings one and three, but not two. An applied transverse electric field separates the first moiré conduction band from neighbouring bands, and favors the appearance of correlated insulators at 1/4, 1/2, and 3/4 band filling. Insulating states at 1/4 and 3/4 band filling emerge only in a parallel magnetic field (B||), whereas the resistance at half band filling is weakly dependent on B||. These findings suggest that correlated insulators are favored when a moiré flat band is spectrally isolated, with spin polarization at 1/4 and 3/4 band filling and valley polarization at 1/2 band filling. Copyright © 2019, The Authors. All rights reserved.

关键词： Graphene

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Experimental demonstration of integrated magneto-electric and spin-orbit building blocks implementing energy-efficient logic

Experimental demonstration of integrated magneto-electric an...

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International Electron Devices Meeting (IEDM)

作者： Chia-Ching Lin Tanay Gosavi Dmitri Nikonov Yen-Lin Huang Bhagwati Prasad WonYoung Choi Van Tuong Pham Inge Groen Jun-Yang Chen Mahendra D. C. Huichu Liu Kaan Oguz Emily S. Walker John Plombon Benjamin Buford Carl H. Naylor Jian-Ping Wang Felix Casanova Ramamoorthy Ramesh Ian A. Young Components Research Intel Corporation Hillsboro OR USA Department of Materials Science and Engineering and Department of Physics University of California Berkeley CA USA CIC nanoGUNE Donostia-San Sebastián Basque Country Spain Department of Electrical and Computer Engineering University of Minnesota Minneapolis MN USA Intel Labs Intel Corporation Santa Clara CA USA CQN Intel Corporation Hillsboro OR USA

600 mV magneto-electric switching in 30 nm La-doped BiFeO 3 multiferroic oxide and a proof of concept 7 μV spin-orbit signal output in Pt / CoFe local spin injection device with 100 μA supply current were experimentally demonstrated at room temperature for the 1 st time. Also demonstrated was a path towards 70 mV spin orbit output using Bi 2 Se 3 in a local spin injection device. These are key accomplishments for WRITE and READ building blocks, respectively, toward realization of a magneto-electric spin-orbit (MESO) energy-efficient logic device. Moreover, the 1 st generation of a MESO logic device with a functional READ unit is demonstrated.

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The software-defined metasurfaces concept and electromagnetic aspects

arXiv

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arXiv 2019年

作者： Tasolamprou, Anna C. Pitilakis, Alexandros Tsilipakos, Odysseas Liaskos, Christos Tsiolaridou, Ageliki Liu, Fu Wang, Xuchen Mirmoosa, Mohammad S. Kossifos, Kypros Georgiou, Julius Pitsilides, Andreas Kantartzis, Nikolaos V. Manessis, Dionysios Ioannidis, Sotiris Kenanakis, George Deligeorgis, George Economou, Eleftherios N. Tretyakov, Sergei A. Soukoulis, Costas M. Kafesaki, Maria Foundation for Research and Technology Hellas Heraklion Crete71110 Greece Department of Electrical and Computer Engineering Aristotle University of Thessaloniki Thessaloniki Greece Department of Electronics and Nanoengineering Aalto University P.O. Box 15500 Espoo Finland Department of Electrical and Computer Engineering University of Cyprus Nicosia20537 Cyprus Department of Computer Science University of Cyprus Nicosia20537 Cyprus Fraunhofer IZM Berlin Berlin Center of Advanced Packaging Gustav-Meyer-Allee 25 Berlin Germany Ames Laboratory Department of Physics and Astronomy Iowa State University AmesIA50011 United States Department of Materials Science and Technology University of Crete Heraklion Crete71003 Greece

We present the concept and electromagnetic aspects of HyperSurFaces (HSFs), artificial, ultrathin structures with software controlled electromagnetic properties. The HSFs key unit is the metasurface, a plane with designed subwavelength features whose electromagnetic response can be tuned via voltage-controlled continuously-tunable electrical elements that provide local control of the surface impedance and advanced functionalities, such as tunable perfect absorption or wavefront manipulation. A nanonetwork of controllers enables software defined HSFs control related to the emerging Internet of Things paradigm. Copyright © 2019, The Authors. All rights reserved.

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The limits of near Field Immersion Microwave Microscopy evaluated by imaging bilayer graphene Moiré patterns

arXiv

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arXiv 2020年

作者： Ohlberg, Douglas A.A. Tami, Diego Gadelha, Andreij C. Neto, Eliel G.S. Santana, Fabiano C. Miranda, Daniel Avelino, Wellington Watanabe, Kenji Taniguchi, Takashi Campos, Leonardo C. Ramirez, Jhonattan C. do Rego, Cássio Gonçalves Jorio, Ado Medeiros-Ribeiro, Gilberto Microscopy Center Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil Electrical Engineering Graduate Program Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil Physics Department Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil Instituto de Física Universidade Federal da Bahia Campus Universitário de Ondina Salvador - BA40170-115 Brazil 1-2-1 Sengen Tsukuba-cityIbaraki305-0047 Japan Department of Electronic Engineering School of Engineering Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil Technology Innovation Graduate Program Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil Computer Science Department Universidade Federal de Minas Gerais Belo HorizonteMG31270-901 Brazil

Molecular and atomic imaging required the development of electron and scanning probe microscopies to surpass the physical limits dictated by diffraction [1]. Nano-infrared experiments [2] and pico-cavity tip-enhanced Raman spectroscopy imaging later demonstrated that radiation in the visible range [3] can surpass this limit by using scanning probe tips to access the near-field regime [4]. Here we show that ultimate resolution can be obtained by using scanning microwave imaging microscopy to reveal structures with feature sizes down to 1 nm using a radiation of 0.1 m in wavelength. As a test material we use twisted bilayer graphene, which is not only a very important recent topic due to the discovery of correlated electron effects such as superconductivity [5], but also because it provides a sample where we can systematically tune a superstructure Moiré patterńs modulation from below one up to tens of nanometers. By analyzing the tip-sample distance dynamics, we demonstrate that this ultimate 108 probe-to-pattern resolution can be achieved by using liquid immersion microscopy concepts and exquisite force control exerted on nanoscale water menisci. Copyright © 2020, The Authors. All rights reserved.

关键词： Moire fringes

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Entanglement properties of disordered quantum spin chains with long-range antiferromagnetic interactions

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Physical Review B 2020年第21期102卷 214201-214201页

作者： Y. Mohdeb J. Vahedi N. Moure A. Roshani Hyun-Yong Lee R. N. Bhatt Stefan Kettemann Stephan Haas Department of Physics and Earth Sciences Jacobs University Bremen Bremen 28759 Germany Technische Universität Braunschweig Institut für Mathematische Physik Mendelssohnstr. 3 38106 Braunschweig Germany Department of Physics Sari Branch Islamic Azad University Sari 48164-194 Iran Department of Physics and Astronomy University of Southern California Los Angeles California 90089-0484 USA Department of Applied Physics Graduate School Korea University Sejong 30019 Korea Division of Display and Semiconductor Physics Korea University Sejong 30019 Korea Interdisciplinary Program in EċICT-Culture-Sports Convergence Korea University Sejong 30019 Korea Department of Electrical Engineering Princeton University Princeton New Jersey 08544 USA School of Natural Sciences Institute for Advanced Study Princeton New Jersey 08540 USA Division of Advanced Materials Science Pohang University of Science and Technology (POSTECH) Pohang 790-784 Korea

Entanglement measures are useful tools in characterizing otherwise unknown quantum phases and indicating transitions between them. Here we examine the concurrence and entanglement entropy in quantum spin chains with random long-range couplings, spatially decaying with a power-law exponent α. Using the strong disorder renormalization group (SDRG) technique, we find by analytical solution of the master equation a strong disorder fixed point, characterized by a fixed point distribution of the couplings with a finite dynamical exponent, which describes the system consistently in the regime α>12. A numerical implementation of the SDRG method yields a power-law spatial decay of the average concurrence, which is also confirmed by exact numerical diagonalization. However, we find that the lowest-order SDRG approach is not sufficient to obtain the typical value of the concurrence. We therefore implement a correction scheme which allows us to obtain the leading-order corrections to the random singlet state. This approach yields a power-law spatial decay of the typical value of the concurrence, which we derive both by a numerical implementation of the corrections and by analytics. Next, using numerical SDRG, the entanglement entropy (EE) is found to be logarithmically enhanced for all α, corresponding to a critical behavior with an effective central charge c=ln(2), independent of α. This is confirmed by an analytical derivation. Using numerical exact diagonalization (ED), we confirm the logarithmic enhancement of the EE and a weak dependence on α. For a wide range of partition size l, the EE fits a critical behavior with a central charge close to c=1, which is the same as for the clean Haldane-Shastry model with a power-law-decaying interaction with α=2. Only for small l≪L, in a range which increases with the number of spins N, we find deviations which are rather consistent with the strong disorder fixed point central charge c=ln(2). Furthermore, we find using ED that the conc

关键词： Magnetism Quantum entanglement Disordered systems Doped semiconductors Density matrix methods Exact diagonalization Renormalization group Tensor network methods

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