研究领域
My research interests are in experimental condensed matter physics. We synthesize and characterize novel materials with unusual electronic and magnetic ground states, including low-dimensional and nanoscale structures. Examples are charge- and spin-density-wave conductors, superconductors, giant magnetoresistance materials, fullerenes, and nanotubes. Experimental characterization techniques include structural measurements (TEM, X-ray scattering) and the examination of general transport coefficients (dc and high frequency conductivity, Hall effect, thermal conductivity, thermopower), high magnetic field studies, high pressure effects, and velocity of sound. In addition we operate a high magnetic field cryogenic STM capable of manipulating and assembling individual atoms into interesting structures.
Current Projects
High-temperature superconductors: We synthesize polycrystalline, single crystal, and thin film and superlattice specimens of high-Tc oxide superconductors such as Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O, and Hg-Ba-Ca-Cu-O, and perform isotope effect, intercalation, and magnetotransport studies. The goal is to understand the normal state transport and the mechanism of superconductivity. New superconductors have been synthesized and are being used to test theoretical models. Vortex (Abrikosov and Josephson) dynamics are studied in applied magnetic fields to 17.5 Tesla.
Fullerene-based conductors and superconductors: Fullerenes such as the soccer-ball-shaped molecule C60 are the basis for interesting conductors and superconductors. We intercalate C60 single crystals with alkali metals and study isotope effects (both alkali and cabon), general transport, magnetotransport, and high pressure effects. The C60 molecules can be polymerized into quasi-one-dimensional chains. These new air-stable conducting crystals display unusual phase transitions that we examine via conductivity, specific heat, x-ray scattering, and STM.
Nanotubes: It is possible to arrange carbon atoms into near-perfect nanotubes— structures with diameters on the order of 10Å to 1000Å and lengths over 100µm. Theoretically, these tubes are the strongest possible fiber, and they are predicted to have unusual electronic properties (some are conductors, others insulators). We fabricate carbon nanotubes and measure their structure via TEM and electrical and mechanical properties using other techniques. It is possible to fill the tubes with other atoms, and to collapse the tubes into flat, flexible ribbons. In addition, it has been predicted that nanotubes containing boron and nitrogen, BxCyNz, may have many properties superior to carbon nanotubes for applications purposes. We synthesize such tubes and study their properties.
Giant magnetoresistance materials: Materials such as La-Ba-Mn-O are semiconductor-like at high temperature and metal-like (with magnetic ground states) at low temperature. In the intermediate temperature regime (typically somewhat below room temperature), they may display an unusually large negative magnetoresistance. We study the magnetoresistance and other transport properties in order to understand the conduction and scattering mechanisms.
Atomic-scale manipulation: We have designed and constructed a unique high-speed, high-field, cryogenic UHV scanning tunneling microscope capable of assembling and measuring the electronic properties of nanoscale structures, including superconductors and nanotubes.
近期论文
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A. Yan, W. Chen, C. Ophus, J. Ciston, Y. Lin, K. Persson, and A. Zettl. Identifying different stacking sequences in few-layer CVD-grown MoS2 by low-energy atomic-resolution scanning transmission electron microscopy. Phys. Rev. B, 93, 041420(R) doi: 10.1103/PhysRevB.93.041420 (2016).
H. Long, A. Harley-Trochimczyk, T. He, T. Pham, Z. Tang, T. Shi, A. Zettl, W. Mickelson, C. Carraro, and R. Maboudian. In situ localized growth of porous tin oxide films on low power microheater platform for low temperature CO detection. ACS Sensors, doi: 10.1021/acssensors.5b00302 (2016).
J. Velasco, Jr., L. Ju, D. Wong, S. Kahn, J. Lee, H.-Z. Tsai, C. Germany, S. Wickenburg, J. Lu, T. Taniguchi, K. Watanabe, A. Zettl, F. Wang, and M.F. Crommie. Nanoscale control of rewriteable doping patterns in pristine graphene/boron nitride heterostructures. Nano Lett. 16, 3, pp1620-1625, doi: 10.1021/acs.nanolett.5b04441 (2016).
Y. Sasaki, R. Kitaura, J.M. Yuk, A. Zettl, and H. Shinohara. Efficient preparation of graphene liquid cell utilizing direct transfer with large-area well-stitched graphene. Chem Phys Lett. 650, pp 107-112, doi: 10.1016/j.cplett.2016-02-066 (2016).
H. Long, A. Harley-Trochimczyk, T. Pham, Z. Tang, T. Shi, A. Zettl, C. Carraro, M.A. Worsley, and R. Maboudian. High Surface Area MoS2/Graphene Hybrid Aerogel for Ultrasensitive NO2 Detection. Advanced Functional Materials, doi: 10.1002/adfm.201601562 (2016).
J. Lee, D. Wong, J. Velasco, Jr., J.F. Rodriguez-Nieva, S. Kahn, H.-Z. Tsai, T. Taniguchi, K. Watanabe, A. Zettl, F. Wang, L.S. Levitov, and M.F. Crommie. Imaging Electrostatically Confined Dirac Fermions in Graphene Quantum Dots. Nat Phys. doi: 10.1038/nphys3805 (2016).
S. Onishi, M.M. Ugeda, Y. Zhang, Y. Chen, C. Ojeda-Aristizabal, H. Ryu, S.-K. Mo, Z. Hussain, Z.-X. Shen, M.F. Crommie, and A. Zettl. Selenium capped monolayer NbSe2 for two-dimensional superconductivity studies. Phys. Status Solidi B 1521, doi: 10.1002/pssb.201600235 (2016).
H. Rasool, G. Dunn, A. Fathalizadeh, and A. Zettl. Graphene-sealed Si/SiN cavities for high-resolution in situ electron microscopy of nano-confined solutions. Phys. Status Solidi B doi: 10.1002/pssb.201600232 (2016).
H. Reza Barzegar, T. Pham, A.V. Talyzin, and A. Zettl. Synthesis of graphene nanoribbons inside boron nitride nanotubes. Physica Status Solidi B, advance online publication, doi: 10.1002/pssb.201600294 (2016).
O. Ergen, S.M. Gilbert, S.J. Turner, and A. Zettl. Hexagonal boron nitride as a cationic diffusion barrier to form a graded band gap perovskite heterostructure. Physica Status Solidi B, advance online publication, doi: 10.1002/pssb.201600234 (2016).
T. Pham, A.L. Gibb, Z. Li, S.M. Gilbert, C. Song, S.G. Louie, and A. Zett. Formation and dynamics of electron-irradiation-induced defects in hexagonal boron nitride at elevated temperatures. Nano Lett. 2016, 16 (11), p 7142, doi: 10.1021/nanolett.6b03442 (2016).
H.R. Barzegar, A. Yan, S. Coh, E. Gracia-Espino, G. Dunn, T. WÃ¥gberg, S.G. Louie, M.L. Cohen, and A. Zettl. Electrostatically driven nanoballoon actuator. Nano Lett. 2016, 16 (11), p 6787, doi: 10.1021/acs.nanolett.6b02394 (2016).
C. Jin, J. Kim, J. Suh, Z. Shi, B. Chen, X. Fan, M. Kam, K. Watanabe, T. Taniguchi, S. Tongay, A. Zettl, J. Wu, and F. Wang. Interlayer electron-phonon coupling in WSe2/hBN heterostructures. Nat Phys, advance online publication, doi: 10.1038/nphys3928 (2016).
O. Ergen, S.M. Gilbert, T. Pham, S.J. Turner, M.T.Z. Tan, M.A. Worsley, and A. Zettl. Graded bandgap perovskite solar cells. Nature Materials advance online publication, doi: 10.1038/NMAT4795 (2016).
T. Sun, J. Kim, J.M. Yuk, A. Zettl, F. Wang, and C. Chang-hasnain. Surface-normal electro-optic spatial light modulator using graphene integrated on a high-contrast grating resonator. Optics Express 24, 23, doi: 10.1364/OE.24.026035 (2016).
X. Ye, M.R. Jones, L.B. Frechette, Q. Chen, A.S. Powers, P. Ercius, G. Dunn, G.M. Rotskoff, S.C. Nguyen, V.P. Adiga, A. Zettl, E. Rabani, P.L. Geissler, and A.P. Alivisatos. Single-particle mapping of nonequilibrium nanocrystal transformations. Science, 354, 6314, p. 874, doi: 10.1126/science.aah4434 (2016).
S. Dai, Q. Ma, Z. Fei, M. Liu, M.D. Goldflam, T. Andersen, W. Gannett, Will Regan, M. Wagner, A.S. McLeod, A. Rodin, S.-E. Zhu, K. Watanabe, T. Taniguchi, G. Dominguez, M. Thiemens, A.H. Castro Neto, G.C.A.M. Janssen, A. Zettl, F. Keilmann, P. Jarillo-Herrero, M.M. Fogler, and D.N. Basov. Hyperbolic phonon polaritons in hexagonal boron nitride. (Conference Presentation) Proc. SPIE 9918, Metamaterials, Metadevices, and Metasystems 2016, 99181Q, doi: 10.1117/12.2236367 (2016).
Z. Fei, J.J. Foley IV, W. Gannett, M.K. Liu, S. Dai, G.X. Ni, A. Zettl, M.M. Fogler, G.P. Wiederrecht, S.K. Gray, and D.N. Basov. Ultraconfined plasmonic hotspots inside graphene nanobubbles. Nano Lett. Articles ASAP, doi: 10.1021/acs.nanolett.6b04076 (2016).
S. Wickenburg, J. Lu, J. Lischner, H.-Z. Tsai, A. Omrani, A. Riss, C. Karrasch, A. Bradley, H.S. Jung, R. Khajeh, D. Wong, K. Watanabe, T. Taniguchi, A. Zettl, A. Castro Neto, S. Louie, and M. Crommie. Tuning charge and correlation effects for a single molecule on a graphene device. Nat Comm 7, 131553, doi: 10.1038/ncomms13553 (2016).
J. Park, V.P. Adiga, A. Zettl, and A.P. Alivisatos. High resolution imaging in the graphene liquid cell. In Liquid Cell Electron Microscopy, F.M. Ross, ed. (Cambridge University Press, Cambridge, U.K., 2017) p. 393
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