Argonne National Laboratory

Seminar Series

Date Title

April 20, 2018

2:00 pm

Bldg. 440, Room A105/A106

Investigating host-guest interactions in two dimensional supramolecular networks, Thomas A. Jung, Paul Scherrer Institute and University of Basel, Switzerland.  Host: Saw Wai Hla

 

Future quantum technologies, for example, rely on the detailed understanding of the interaction between different well-defined electronic states. Surface supported atomic and molecular systems provide a base for such investigations with the particular advantage of addressability. In our work we establish on-surface architectures which exhibit extraordinary local e.g. electronic, magnetic and quantum properties originating from the reduced dimensionality of the self-assembled and atomically precise architectures. Quantum well arrays, for example, can be produced by the interaction of porous on-surface networks with 2D Shockley-type surface states. Interestingly the periodicity of these (lossy) confinements causes band formation by the coupling between the individual quantum well [1]. In our more recent work the quantum wells have been modified by the adsorption / condensation of Xe atoms [2,3]. Localized and delocalized electronic states can be identified across the 2D array as they lead to new, site-specific physical and chemical behavior.

 

Sublattices in 2D ‘checkerboard’ architectures of magnetic molecules on magnetic substrates can be selectively switched by chemical ligation [4]. Also we have observed the first example of 2D ferrimagnetic long-range order and remanence for such a 2D architecture on non-magnetic Au(110) [5]. Uniquely, self-assembled 2D architectures contribute to our understanding of fundamental interactions involved in host-guest systems and allow for the specific operation of quantum states with a partial delocalization delocalized by the supramolecular on-surface architecture.
 
[1] Lobo-Checa, J. et al., Science 325:300 (2009)
[2] Nowakowska, S. et al., Nat. Commun. 6:6071 (2015)
[3] Nowakowska, S. et al., Small 12:3757 (2016)
[4] Ballav N., et al., JPCL 4:2303 (2013)
[5] Girovsky, J. et al., Nat. Commun., DOI: 10.1038/ncomms15388 (2017).
 

April 20, 2018

11:00 am

Bldg. 400, Conf. Rm A105/A106

Data Driven 4-D X-ray Imaging of Nanoscale Dynamics, Mathew J. Cherukara, Advanced Photon Source, Argonne National Laboratory.  Host:  Martin Holt

Observing the dynamic behavior of materials following ultra-fast excitation can reveal insights into the response of materials under non-equilibrium conditions of pressure, temperature and deformation. Such insights into materials response under non-equilibrium is essential to design novel materials for catalysis, low-dimensional heat management, piezoelectrics, and other energy applications. However, material response under such conditions is challenging to characterize especially at the nano to mesoscopic spatiotemporal scales. Time-resolved coherent diffraction imaging (CDI) is a unique technique that enables three-dimensional imaging of lattice structure and strain on sub-ns timescales. In such a ‘pump-probe’ technique, stroboscopic x-ray ‘probes’ are used to image the transient response of a sample following its excitation by a laser ‘pump’. In this talk I will present some of our recent work on imaging and modeling of phonon transport and lattice dynamics in nanomaterials. I will also describe my work in the use of deep neural networks in accelerating the analysis of and increasing the robustness of image recovery from 3D X-ray diffraction data. Once trained, our deep neural networks are thousands of times faster than traditional phase retrieval algorithms used for image reconstruction from 3D diffraction data.

April 16, 2018

11:30 am

Bldg. 440, Conf. Rm A105/A106

Geometric Charges and Kirigami,  Michael Moshe, Host:  Daniel Lopez

Kirigami patterns generate non-trivial three dimensional behavior from perforated sheets, and so offer a promising means for developing mechanical metamaterials. To create a generic account of the mechanical behavior of kirigami, we study the unit cell of a typical kirigami structure: an isolated frame. The mechanical behavior of the entire sheet may then be understood in terms of the coupling of many individual frames.

Recent developments in a geometric formulation of elasticity theory paved the way for a mathematical description of such isolated frames using the concept of “geometric charges". In this approach the mechanical problem of Kirigami and coupled frames is transformed to a simpler problem of interacting geometric charges.
 
In this talk I will present experimental and theoretical results on the relation between Kirigami, the geometric approach to elasticity, and geometric charges. I will show how these results provide  simple rules for designing nontrivial Kirigami patterns.

April 2, 2018

11:00 am

Bldg. 440, Conf. Rm A105/A106

X-ray Studies of the Structure and Properties of Materials During Synthesis and Processing, Matt Highland,  Materials Science Division,  Argonne National Laboratory.  Host:  Martin Holt
 
The properties and functionality of a material depends on its structure as well as its interactions with other materials and its environment. Understanding the nature of these interactions will allows use to create new models and define new methodologies for making materials with desired properties. Gaining this understanding requires experimental techniques that allow us to probe the local structure, phase, and strain of a material system during synthesis and processing, within a larger structure, or under excitation. A variety of x-ray techniques are available to address these challenges. I will describe experiments in which we have used a number of these techniques to probe materials during synthesis, high temperature processing, and ultra-fast excitation. I will discuss how this work provides insight into roles that microstructure and local strain fields play in defining the properties of a material and describe a number of projects motivated by these studies.

March 29, 2018

11:00 am

Bldg. 440, Conf. Rm. A105/A106

Quantum Ordering and Mesoscale Dynamics Unraveled by Focused Coherent X-ray Beams, Qingteng Zhang, XSD, ANL. Host: Martin Holt
 
An ongoing scientific thrust is pushing forward a deeper understanding of the rich correlation between electronic, spin, orbital orderings and atomic lattice in quantum materials. A recent study at the Hard X-ray Nanoprobe (HXN) in Center for Nanoscale Materials (CNM) has shown that quantum ordering can be enhanced in patterned nanostructures [1], providing new venues for the manipulation of quantum structures and exciting opportunities for the design and engineering of functional nanomaterials. One of the science cases is ferroelectric nanodomains in thin atomic layers of complex oxides. Ferroelectric polarization in epitaxial nominal atomic layers often forms into striped nanodomains to minimize the total electrostatic energy of the system. Domain walls provide versatile control of thin film properties because domains are easily reconfigurable and intriguing properties arise at domain walls due to the very large atomic strain caused by abrupt change of polarization direction. In a 100 nm thick PbTiO3/SrTiO3 superlattice, the electric coupling between the ferroelectric PbTiO3 layers is tuned by the SrTiO3 layers and results in nm-periodicity domains with serpentine striped patterns commonly observed in spinodal decomposition systems. This seminar will show that the ferroelectric nanodomains can exhibit thermally-driven equilibrium dynamics [2] similar to the Brownian motions [3] and gelation-induced arrested dynamics of colloidal nanoparticles [4], albeit on a much slower timescale of thousands of seconds. The temperature dependence on the time scale of domain fluctuation can be described using Arrhenius equation yielding an activation energy of 0.35 ± 0.21 eV. This energy level corresponds to the average energy barrier height that separates energetically degenerate domain configurations and implies that the formation and fluctuation of nanodomains may be affected by pinning mechanisms such as oxygen ion vacancies.
 
The seminar will also discuss possible prospective areas of research at the HXN, including a systematic investigation on the size-dependence of quantum orderings in patterned nanostructures which plans to leverage the resources of CNM, and speckle analysis using pattern recognition and deep learning which plans to leverage the computing resources at ALCF.
 
 
References:
[1]. J. Park, J. Mangeri, Q. Zhang et al. Nanoscale 10, 3262 (2018)
[2]. Q. Zhang et al. Phys. Rev. Lett. 118, 097601 (2017)
[3]. Q. Zhang et al. J. Synchrotron. Rad. 63, 679 (2016)
[4]. Q. Zhang et al. Phys. Rev. Lett. 119, 178006 (2017)
 

March 15, 2018

2:00 pm

Bldg. 440, Conf. Rm. A105/A106

Antimicrobial Photodynamic Therapy with Ga-Protoporphyrin Derivatives Against Pathogenic Bacteria, Ana Morales-de-Echegaray, Wei Research Lab, Department of Chemistry, Purdue University.  Host:  Tijana Rajh.

Bacterial pathogens have the ability to acquire hemin through different mechanisms. One mechanism is through cell-surface hemin receptors (CSHRs), which are capable of rapid hemin recognition and make the bacteria vulnerable to antimicrobial photodynamic inactivation (aPDI). The work presented here focuses on gallium protoporphyrin IX (GaPpIX) as a photosensitizer for aPDI against staphylococci. GaPpIX is rapidly uptaken into CSHR-expressing bacteria, and is easily detected within minutes of exposure. Assessment of GaPpIX as a photosensitizer against laboratory strains of Staphylococcus aureus, clinical isolates of methicillin-resistant S. aureus (MRSA), and S. epidermis shows aPDI activity at low micromolar levels, following 15 minutes of exposure to a compact fluorescent light bulb or at nanomolar levels when exposed for 10 seconds with a light emitting diode (LED) light source. Activity also had greater potency when compared against metal-free protoporphyrin (PpIX). These results led to the design of a more potent photosensitizer by incorporating GaPpIX into apohemoglobin (GaPpIXHb) and using the hybrid protein to coat 10-nm silver nanoparticles (AgNPs). The GaPpIXHb-AgNP complexes exhibit remarkable aPDI activity using nanomolar loadings of GaPpIX against clinical MRSA isolates.

March 1, 2018

11:00 am

Bldg. 440, Conf. Rm. A105/A106

Emergent Topology in Artificial Graphenes, Xiao Hu, International Center for Materials Nanoarchitectronics (WPI-MANA), National Institute for Materials Science (NIMS), Tsukuba, Japan.  Host: Ulrich Welp

 

Honeycomb lattice plays an important role in the course of fostering topology physics as known from the Haldane model and the Kane-Mele model [1]. Recently we formulate a new way to achieve topological states exploiting the C6v symmetry of honeycomb structure, which can be applied to various artificial graphenes with tremendous recent interests. As the first example we show how to realize topological electromagnetic transportations in dielectric photonic crystals, which has been proved by recent experiments [2,3,4]. This idea can also be applied to fermionic systems, and especially we find topological electronic states protected by huge energy gaps in order of eV in graphene with regular nano-hole arrays [5,6,7]. Our approach provides a new facet for exploration of novel topological phenomena and functionalities in terms of advanced nanotechnologies.

 References: [1] H.-M. Weng, R. Yu, X. Hu, X. Dai and Z. Fang: Adv. Phys. vol. 64, 227 (2015).  [2] L.-H. Wu and X. Hu: Phys.  Rev. Lett. vol. 114, 223901 (2015).  [3] Y.-T. Yang, J.-H. Jiang, X. Hu and Z.-H. Hang: arXiv.1610.07780.  [4] Y. Li, H. Chen and X. Hu et al.: arXiv:1801.04395.  [5] L.-H. Wu and X. Hu: Sci. Rep. vol. 6, 24347 (2016).  [6] T. Kariyado and X. Hu: Sci. Rep. vol. 7, 16515 (2017).  [7] T. Kariyado, Y.-C. Jiang, H.-X. Yang and X. Hu: arXiv:1801.03115.

Feb. 21, 2018

2:00 pm

Bldg. 440, Room A105/A106

"Deep Learning Applied to Simulation of 2d Materials", Isaac Tamblyn, Security and Discuptive Technologies, National Research Council of Canada. Host:  Pierre Darancet In this talk,

I'll show how we are using Artificial intelligence as a new tool to improve computer models of physical and chemical processes at the nanoscale. In particular, I'll discuss how we show how to rapidly solve the Schrödinger Equation [1], predict phase transitions [2], estimate the strength of chemical bonds [3], provide a confidence level for our predictions [4], and achieve a million times speed up in simulating a nanostructured 2d-material [5].

[1] K. Mills, M. Spanner, I. Tamblyn, Deep learning and the Schrödinger equation Phys. Rev. A 96, 042113 (2017), arXiv:1702.01361
 
[2] K. Mills, I. Tamblyn, Deep neural networks for direct, featureless learning through observation: the case of 2d spin models, arXiv:1706.09779
 
[3] K. Ryczko, K. Mills, I. Luchak, C. Homenick, I. Tamblyn, Convolutional neural networks for atomistic systems, arXiv:1706.09496 
 
[4] K. Mills, I. Tamblyn, Phase space sampling and operator confidence with generative adversarial networks, arXiv:1710.08053
 
[5] I. Luchak, K. Mills, K. Ryczko, A. Domurad, I. Tamblyn, Extensive deep neural networks, arXiv:1708.06686
 
 

Feb. 20, 2018

11:00 am

Bldg. 440, Room A105/A106

"Scattering Studies of a Micron-sized Gold Particle and Average Nanoparticles", Milan K. Sanyal,Saha Institute of Nuclear Physics Kolkata, West Bengal, India.  Host:  Martin Holt

Availability of intense synchrotron sources delivering nano-sized beam should be able to provide us structure, composition and strain profiles within a nanoparticle from averaged information obtained over only few such particles and finally may be even from an individual particle. We shall discuss here few evolving x-ray scattering techniques with the help of three recently studied systems, namely distribution of non-FCC phase in a micron-sized gold particle, shape-evolution in gold nanoparticles grown in nano-pores and extraction of compositional profile of an average III-V semiconductor quantum-dot - the size-tunable photonic material.

Feb. 13, 2018

10:30 am

Bldg. 440, Room A105/A106

"Materials and Processing for Quantum Computing - Ion Traps and Superconductors", David P. Pappas, National Institute of Standards and Technology, Boulder.  Host:  Ilke Arslan.

A brief description and history of quantum computing will be presented. Materials topics relevant to ion traps and superconductors will be presented. For the ion traps, the influence of anomalous surface noise on gate operations will discussed. Progress at NIST to study and mitigate these effects will be presented. These include cleaning, surface spectroscopy and scanned probe microscopy as well as a novel stylus trap to measure noise from proximal surfaces. In the second part of the talk similar topics on superconducting transmons will be discussed. In particular, the effects and mitigation techniques of spurious two-level systems at surfaces and interfaces as well as new scalable techniques for fabricating junctions will be presented.

Feb. 2, 2018

2:00 pm

Bldg. 440, Room A105/A106

"Flexible Electronics Based on Two-Dimensional Materials and Beyond", Xu Zhang, Massachusetts Instittue of Technology. Host:  Daniel Lopez

The success in creating atomically thin and mechanically robust two-dimensional (2D) materials has unveiled new possibilities for next generation of flexible and ubiquitous electronics. One critical distinction between 2D crystals and 3D crystals is that 2D crystals are all-surface materials. Therefore, it is essential to understand how 2D materials interact with their environments and how this interaction impacts their electronic properties. A suite of X-ray techniques is used to investigate how the functionalizing dopants impact the electronic and chemical states of graphene. Based on this study, we develop an effective and non-invasive doping method for graphene through plasma-based chlorination. In the second part of this talk, I will focus on system-level applications of 2D materials-based flexible electronics with a special focus on wireless energy harvesting and communication. In particular, we developed a 2D material-based GHz flexible rectifier as an enabling component for both wireless energy harvesting and RF frequency mixing. It is the first flexible rectifier operating up to the X-band and it fully covers the Wi-Fi channels. By integrating with an antenna, the MoS2-enabled rectenna successfully demonstrates direct energy harvesting of electromagnetic (EM) radiation in the Wi-Fi band and lights up a commercial light-emitting diode (LED) with zero external bias (battery-free).

Feb. 1, 2018

2:00 pm

Bldg. 440, Room A105/A106

"Novel transport characterizations in anisotropic and disordered", Lintao Peng, Northwestern University, Electrical Engineering and Computer Science.  Host:  Nathan Guisinger

New electrical transport techniques are introduced for characterization of exfoliated black phosphorous devices. First, an all-electrical conformal-5-contact method is proposed to determine the crystal orientation of an exfoliated flake. Second, the disorder-related switching transient conductivity, and a microscopic DOS model thereof, are discussed within the framework of dispersive diffusion transport and continuous time random walk. Finally, the observation of a disorder-scaling behavior in gate-dependent conductivity is presented and modeled.

Jan. 24, 2018

3:30 pm

Bldg. 440, Room A105/A106

"Light- and heat-managing nanomaterials for personal health and energy efficience", Po-Chun Hsu, Department of Mechanical Engineering, Stanford University.  Host:  Supratik Guha

Energy and health are the two vital necessities for humans. While energy is indispensable, it also produces greenhouse gas emission and climate change. In the US, 12% of total energy is used for maintaining indoor temperatures, which is the fundamental need for human health. Therefore, it is crucial to reduce the building energy consumption while maintaining thermal comfort. In this talk, I will present several nanomaterials that can manage photons and heat transfer to enhance building energy efficiency and personal health. The first part is the personal thermal management by controlling radiation heat transfer, which contributes 50% of the human body heat dissipation. I will demonstrate infrared-reflective nanowires textile for heating, infrared-transparent nanoporous polyethylene for cooling, and asymmetrical emitter to achieve both heating and cooling. The second part is transparent electrodes and electrochromic smart windows for solar heat gain modulation. Fabricated by electrospinning, the metal nanofiber transparent electrodes with superior electrical and optical properties and durability can improve the speed and cycle life of electrochromic windows.

Jan. 11, 2018

11:00 am

Bldg. 440, Room A105/A106

"There's Plenty of Room in Higher Dimensions - Internal Resonance and Decision Mechanisms in Mechanical Resonators", Axel Eriksson, Chalmers University of Technology, Sweden.  Host:  David Czaplewski. 

To understand how adaptive behavior emerges in living and artificial systems is a major challenge for science. In this talk, I consider something simpler – dead vibrating silicon beams and graphene membranes. I will give a short introduction to nonlinear dynamics of vibrational modes in mechanical resonators. An interesting situation occurs when two vibrational modes have a rational relation between their frequencies – a so called internal resonance. The match in frequency allows for efficient transfer of energy between the two modes. Hence, the internal resonance will strongly affect both the dissipation and the driven response of the resonator. The complex response has similarities with other strongly nonlinear systems such as interacting neurons in the brain. Furthermore, the driven response may exhibit choice mechanisms leading to stochastic switching between different long-term behaviors. In future work, we plan to experimentally control this switching as a means to achieve primitive adaptive behavior in mechanical resonators.