Argonne National Laboratory

2017 Colloquium Archive

Date Title
Dec. 13, 2017 "Mimics of chemical barrier crossing to strange "non-reciprocal" dynamics in Optical matter", Norbert Scherer, University of Chicago, Host: Xiao-Min Lin
The interaction of light with matter is one of the primary means employed to understand the world around us, particularly from atomic and molecular scales and up. However, electromagnetic radiation can also be used to generate forces and momentum on systems for active manipulation. While these forces are relatively weak on macro-scales, they have realized great impact on  the (sub-)microscale in biophysics, cell biology and nanoscience. This talk will present another direction - the creation of optical matter from nanoparticle building blocks by optical binding forces - to study barrier crossing phenomena in chemistry and the manifestation of non-reciprocal (non-conservative) dynamics. The new insights into barrier crossing and the applicability of widely-used theoretical descriptions based on Kramers theory are made possible by direct visualization of single particle dynamics vs. the unseeable dynamics that occur at the molecular level in Chemistry and Biophysics. Understanding (apparent) non-conservative dynamics of multi-particle optical matter systems, as manifest in "negative torque" and linear motion that seem to defy the actio et reactio principle of classical Physics requires considering optical matter as a many body system/problem with all-to-all relatively long range electrodynamic interactions. 
Nov. 15, 2017  "Directed Self-Assembly of Performance Materials",  Paul Nealey, Institute for Molecular Engineering/University of Chicago/Argonne National Laboratory, Host: Xuedan Ma
Directed self-assembly is arguably the most promising strategy for high-volume cost-effective manufacturing at the nanoscale.  Over the past decades, manufacturing techniques have been developed with such remarkable efficiency that it is now possible to engineer complex systems of heterogeneous materials at the scale of a few tens of nanometers. Further evolution of these techniques, however, is faced with difficult challenges not only in feasibility of implementation at scales of 10 nm and below, but also in prohibitively high capital equipment costs. Materials that self-assemble, on the other hand, spontaneously form nanostructures down to length scales at the molecular scale, but the micrometer areas or volumes over which the materials self-assemble with adequate perfection in structure is incommensurate with the macroscopic dimensions of devices and systems of devices of industrial relevance.  Directed Self-Assembly (DSA) refers to the integration of self-assembling materials with traditional manufacturing processes.  The key concept of DSA is to take advantage of the self-assembling properties of materials and at the same time meet the constraints of manufacturing.  Put another way, DSA enables current manufacturing process capabilities to be enhanced and augmented at drastically reduced cost. Here I will discuss the use of lithographically-defined chemically patterned surfaces to direct the assembly of block copolymer films for semiconductor manufacturing and the design of ion-conducting membranes for energy applications, liquid crystal based systems for optoelectronics, and nanoparticles for applications in nanophotonics.  In addition, I will highlight how DSA of these systems enables new strategies and techniques for characterization and optimization of both materials and processing conditions.
Nov. 1, 2017 "Adventures in Scalable Nano-manufacturing: Novel Materials and Processes For Goals in Sustainability and Low-Cost Chemical Sensing”,  Alexander Wei, Purdue University.  Host: Xiao-Min Lin
As the field of nanotechnology continues to mature, emphasis is gradually shifting from discovery and immediate application to process development, systems integration, and sustainability. In this seminar, we will highlight studies in which discovery-driven research paved the way toward goals in scalable and sustainable nano-manufacturing using a team science approach, featuring research efforts from my own laboratory and at the Birck Nanotechnology Center at Purdue.  Topics include (i) the scalable synthesis of nanoparticles with plasmonic and magnetic function (magnetic gold nanoclusters) and their role as etchants in the fabrication of nanoporous membranes, (ii) the incorporation of nano-cellulose into composite materials with a reduced carbon footprint, and (iii) current efforts to develop cost-effective chemical sensors, using materials generated by the first two efforts.
Oct. 18, 2017 "Structure-Property Relationships to Nanostructured Materials: Aqueous Semiconductor Interfaces", Mark Hybertsen,  National Laboratory, Center for Functional Nanomaterials.  Host:  Pierre Darancet
Understanding structure-property relationships in fields as diverse as nanoscale electronic junctions, heterogeneous catalysis, electrochemistry and energy storage often starts by meeting the challenge of identifying key structure motifs.  For the theorist this is followed by tackling the problem of calculating the relevant functional characteristics, also challenging, particularly for excited state properties. I will discuss the modern toolbox for these problems, including a brief outline of the basic physical ingredients of modern many-body perturbation theory which enables studies of excited state properties.  I will then discuss its application in the context of the search to develop new materials for use in photocatalysis.  In particular, I will discuss the search for key structural motifs at semiconductor-water interfaces and the connection to electrochemical energy level alignment.
Sep. 20, 2017 "Physical Principles for Complex Energy Materials from Ab Initio Computational Methods", Jeffrey Neaton, Lawrence Berkeley National Laboratory.  Host:  Pierre Darancet.
The ability to identify and design new materials for energy applications hinges on the development of intuition connecting their properties to chemical composition, atomic-scale structure, dimensionality, and environment. Here I will describe the development and application of new ab initio computational approaches – based on density functional theory, many-body perturbation theory, and materials databases – for prediction of energy conversion phenomena in complex materials. First, I will describe a new formalism and calculations that sheds new light into singlet fission, a multiexciton generation process by which multiple charge carriers may ultimately result from a single photon. Second, I will discuss a new joint experiment and theory high-throughput workflow for identifying a new class of vanadium oxide-based photoanode materials for solar fuels applications. In both cases, I will highlight new intuition and methods developed in these studies, and provide a perspective on future work.
Sep. 12, 2017  "Probing Neural Function with Electronic, Optical and Magnetic Materials", Polina Anikeeva, Massachusetts Institute of Technology (MIT).  Host:  Elena Shevchenko
Mammalian nervous system contains billions of neurons that exchange electrical, chemical and mechanical signals. Our ability to study this complexity is limited by the lack of technologies available for interrogating neural circuits across their diverse signaling modalities without inducing a foreign-body reaction. My talk will describe neural interface strategies pursued in my group aimed at mimicking the materials properties and transduction mechanisms of the nervous system. Specifically, I will discuss (1) Fiber-based probes for multifunctional interfaces with the brain and spinal cord circuits; (2) Magnetic nanotransducers for minimally invasive neural stimulation; and (3) Active scaffolds for neural tissue engineering and interrogation.
Fiber-drawing methods can be applied to create multifunctional polymer-based probes capable of simultaneous electrical, optical, and chemical probing of neural tissues in freely moving subjects. Similar engineering principles enable ultra-flexible miniature fiber-probes with geometries inspired by nerves, which permit simultaneous optical excitation and recording of neural activity in the spinal cord allowing for optical control of lower limb movement. Furthermore, fiber-based fabrication can be extended to design of scaffolds that direct neural growth and activity facilitating repair of damaged nerves.
Molecular mechanisms of action potential firing inspire the development of materials-based strategies for direct manipulation of ion transport across neuronal membranes. For example, hysteretic heat dissipation by magnetic nanomaterials can be used to remotely trigger activity of neurons expressing heat-sensitive ion channels. Since the alternating magnetic fields in the low radiofrequency range interact minimally with the biological tissues, the magnetic nanoparticles injected into the brain can act as transducers of wireless magnetothermal deep brain stimulation. Similarly, local hysteretic heating allows magnetic nanoparticles to disrupt protein aggregates associated with neurodegenerative disorders.
Location: 446 Auditorium
Sep. 6, 2017
"Optical properties of exciton-plasmon nanomaterials: from collective exciton resonances to nonlinear spectroscopy", Maxim Sukharev, Arizona State University.  Host:  Tal Heilpern
Recent advances in nanofabrication and optical characterization open a wide variety of new ways to improve our understanding of light-matter interaction. In particular, hybrid materials comprised of plasmon sustaining nanostructures and molecular aggregates present a unique opportunity to study how quantum systems (molecules) behave at plasmonic interfaces. The strong coupling phenomenon plays a crucial role allowing to efficiently transfer energy between plasmons and molecular excitons on a femtosecond time scale. In this talk I will discuss modeling aspects of various optical phenomena at plasmonic interfaces using Maxwell-Bloch equations in one, two, and three dimensions. I will demonstrate that at high molecular concentrations exciton-plasmon nanomaterials exhibit a new type of optical resonance related to strong interaction of a molecular aggregate driven by local plasmon fields. I will also discuss photon echo spectroscopy applied to exciton-plasmon systems.
August 9, 2017 "Symmetry protected dirac Fermions in Condensed Matter Systems", Vidya Madhavan, University of Illinois at Urbana-Champaign.  Host:  Jeff Guest Abstract:
Topological insulators host zero mass electrons which can be modeled by the same massless Dirac equation that is used to describe relativistic particles traveling close to the speed of light. In normal topological insulators, the symmetry that protects the Dirac point is time-reversal symmetry.  In this talk I will describe our experimental and theoretical investigations of a distinct class of topological materials called Topological Crystalline Insulators (TCIs) [1,2,3] where crystal symmetry intertwines with topology to create linearly dispersing Fermions similar to graphene. To study this material, we used a scanning tunneling microscopy and landau level spectroscopy [3,4,5]. With the help of our data, I will show how zero-mass electrons and massive electrons can coexist in the same material. I will discuss the conditions to obtain these zero mass electrons as well the method to impart a controllable mass to the particles and show how our studies create a path to engineering the Dirac band gap and realizing interaction-driven topological quantum phenomena in TCIs.
[1] L. Fu, Topological Crystalline Insulators. Phys. Rev. Lett. 106, 106802 (2011)
[2] T. H. Hsieh et al., Topological crystalline insulators in the SnTe material class. Nat.Commun. 3, 982 (2012)
[3] Y. Okada, et al., Observation of Dirac node formation and mass acquisition in a topological crystalline insulator, Science 341, 1496-1499 (2013)
[4] Ilija Zeljkovic, et al., Mapping the unconventional orbital texture in topological crystalline insulators, Nature Physics 10, 572–577 (2014)
[5] Ilija Zeljkovic, et al., Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators, Nature Materials 14, 318–324 (2015)
July 26, 2017
11:00 am
Bldg. 440, A105-106

"Recent Experiments on Materials with Unusual Thermal, Thermoelectric, and Spin-Calortronic Properties"Li Shi, University of Texas at Austin.  Host:  Sridhar Sadasivam

Materials with high or low thermal conductivity and new thermal energy conversion methods can both help to address various technological challenges and stimulate new fundamental studies. Here, we review results from several recent experiments of materials with unusual thermal, thermoelectric, or spin caloritronic properties. Chemical vapor deposition (CVD), chemical vapor transport (CVT), and travelling solvent floating zone methods are employed to grow one- and two- dimensional materials, continuous graphitic network structures, cubic phase boron arsenide with potentially ultrahigh thermal conductivity, and complex crystals with high magnon thermal conductivity or low lattice thermal conductivity. New four-probe electro-thermal and elastic light scattering measurement methods are established to probe the intrinsic thermal transport property and the relaxation length scales of phonons and magnons in these materials. Some of these materials are integrated with electronic and thermal storage devices to enhance the thermal performance.

July 12, 2017
11:00 am
Bldg. 440, A105-106

"Protein Engineering - From Nature to Nanotechnology"Tijana Grove, Virginia Technical Institute, Grove Lab.  Host: Tijana Rajh  

Abstract: Proteins and protein assemblies are the biological workhorses that carry out vital functions in all living organisms. The Grove Lab is interested in translating fundamental knowledge and principles of how proteins operate in nature to the growing field of nanotechnology for the design of multifunctional, dynamic materials. Herein, I will present our most recent work on the repeat-protein biomaterials that self-assemble through the combination of head-to-tail stacking and weak dipole-dipole interactions. These ion and proton conducting materials exhibit anisotropic properties at biologically relevant length-scales, nano to micro, and relevant time scales, miliseconds to seconds.  I will further highlight the tunable anisotropic nano and meso-scale morphologies, which direct the bending, twisting, or curling of material in response to changes in relative humidity and electric potential.  

June 28, 2017
11:00 am
Bldg. 440, A105-106

"Bio-Enigma: High Throughput Screening for Programmable Advanced Materials",  Melik Demirel, Pennsylvania State University.  Host:  Tijana Rajh

Abstract: Recent advances in the nanotechnology of materials combined with parallel improvements in biotechnology and synthetic biology, have demonstrated that more complex biomimetic materials with properties engineered precisely to optimize performance, can be achieved. Specifically, proteins provide unique advantages as advanced materials. For example, proteins can often self-assemble and form network materials with extraordinary properties (PRL’2005) such as extremely high durability or elasticity. More importantly, protein can evolve to new functionalities by gene mutations or duplications, which is unique advantage compared to inorganic materials. Recently, we used a direct correlation between gene duplications and its impact on physical properties to demonstrate that tandem repetition of protein sequences enhances physical properties (PNAS’2016). This method opened the opportunity for the assembly of 2D materials (e.g., graphene, MXene) that are precisely controlled with nm resolution (Carbon’2017) for application in electronic and optical devices. In parallel, we reported the development of a new technique to screen protein evolution based on laser-probing spectroscopy with sub-picosecond resolution (Analyst’2017). Our results demonstrate, for the first time, relative quantification of protein network topology in real time for directed evolution. Hence, combining materials assembly and high-throughput screening, we could answer many fundamental questions in materials research, such as the fundamental long-range order in soft matter as well as development of new tools for advanced materials assembly. Programming physical properties through evolution introduces a new design rule for the understanding of materials design.

June 14, 2017
11:00 am
Bldg. 440, A105-106

"Plasmon-Enhanced Solar Energy Conversion in Semiconductor-Metal Heterojunctions"Nianqiang (Nick) Wu, West Virginia University.  Host:  Gary Wiederrecht

Solar energy can be converted either to electric energy via photovoltaics or to chemical energy via photocatalysts. Emerging of surface plasmon resonance (SPR) provides a new opportunity to improve the performance of photocatalysts and photoelectrochemical cells. This talk will present our effort on fundamental understanding of the underlying mechanism of plasmon-enhanced solar energy harvesting. In particular, the speech will discuss our newly discovered plasmon-induced resonant energy transfer (PIRET) mechanism in the metal-semiconductor heterojunctions. The PIRET mechanism along with the hot electron transfer process suggests that plasmonic nanostructures can act as photo-sensitizers. The discovery of plasmonic photo-sensitizers has opened a new avenue to develop efficient photocatalysts and solar cells. The theoretical maximum efficiency of solar energy conversion in plasmonic metal-semiconductor heterojunctions is predicted. This talk will demonstrate our effort on development of effective plasmonic metal-semiconductor heterojunctions to enable strong coupling between the plasmonic metal and the semiconductor. Our results show that the performance of solar water splitting by a hematite nanorod array can be greatly improved by plasmon-induced photonic and energy transfer enhancement.


May 31, 2017
11:00 am
Bldg. 440, A105-106

"From Model Systems to Efficient Catalytic Materials: One Nanocrystal Fits All"Matteo Cargnello, Stanford University, Department of Chemical Engineering.  Host:  Benjamin Diroll


Catalytic processes are ubiquitous in industry and are crucial for the sustainable development and growth of our society. Many important catalyst discoveries in the past and current century allowed the population to grow, and the quality of life to improve considerably. Despite the incredible importance of these discoveries, edisonian approaches have been used in most cases to find efficient catalysts that could be scaled up to the industrial needs and the growing demand. Unfortunately, these approaches can only take us so far, and new solutions to important challenges are needed. A responsible approach in developing catalytic materials is represented by the design of catalytic sites based on the knowledge of reaction mechanisms and structure-property relationships, and in the precise synthesis of these sites at the atomic and molecular level. To achieve this goal, model systems are used to decrease the complexity of realistic catalytic systems, but it is challenging to relate the models with realistic conditions. In order to fill this gap, nanocrystals, in which size, shape and composition can be accurately tuned close to atomic precision, are emerging as ideal tools that share advantages of model systems, yet can be utilized under realistic conditions as efficient catalytic phases. The goal of this talk is to show how this approach can provide not only fundamental understanding of catalytic reactions, but also represent a way to precisely engineer catalytic sites to produce efficient catalysts that are active, stable and selective for several important catalytic transformations. Examples of this approach will be given in the areas of methane activation, photocatalysis, and in the design of active and stable materials for high-temperature reactions.

May 17, 2017
11:00 am
Bldg. 440, A105-106

"Understanding Complex Biological Systems Using Modeling, Experiments, and Analytics"Payel Das, IBM Thomas J. Watson Research Center.  Host:  Subramanian Sankaranarayanan


Understanding the emerging collective behaviors in complex, dynamic biological systems remains a major challenge. In the first part of my talk, I will discuss use of synergistic experimental-simulation approaches to characterize oligonucleotide dynamics on a biosensor surface and disordered peptide dynamics in solution. In the second part of the talk, I will present application of graph embedding techniques to characterize dynamics of apparently high-dimensional systems, such as peptides and human brain.

May 3, 2017
11:00 am
Bldg. 440, A105-106

"Surface Defected Nanoceria Catalyzing Angiogenesis and its Implications in Wound Care", Sudipta Seal, University of Central Florida:  Host:  Elena Shevchenko


Angiogenesis is the formation of new blood vessels from existing blood vessels and is critical for many physiological and pathophysiological processes. In this study we have shown the unique property of redox active nanoparticles (Re-NPs) to induce angiogenesis, observed using both in vitro and in vivo model systems. In particular, Re-NPs trigger angiogenesis by modulating the intracellular oxygen environment and stabilizing hypoxia inducing factor 1alpha endogenously. Furthermore, correlations between angiogenesis induction and Re-NPs physicochemical properties including: surface valence state ratio, surface charge, size, and shape were also explored. High surface area and mixed valence states make these nanoparticles more catalytically active towards regulating intracellular oxygen, which in turn led to more robust induction of angiogenesis. Atomistic simulation was also used, in partnership with in vitro and in vivo experimentation, to reveal that the surface reactivity of NPs and facile oxygen transport promotes pro-angiogenesis. The talk will conclude with a nanoceria based optoelectronic sensors for biomarker detection.

April 19, 2017
11:00 am
Bldg. 440, A105-106
No Colloquium
April 5, 2017
11:00 am
Bldg. 440, A105-106

"The Emergence of Hybrid Perovskites for High-efficiency Low-cost Optoelectronic Devices", Aditya Mohite, Los Alamos National Laboratory.  Host:  Xuedan Ma


In this talk, I will describe our recent work on Ruddlesden-Popper halide perovskites as a potential alternative to the bulk hybrid perovskites. I will describe the versatility of this novel system through our efforts on achieving photovoltaic devices, photodetectors and light emitting diodes with technologically relevant stability. At the heart of these high performance devices lies an unusual photo-physical behavior where counterintuitive to classical quantum-confined systems where there exists an internal mechanism for the dissociation of excitons to edges of the perovskite layers. These states provide a direct pathway for dissociating excitons into longer-lived free-carriers, which remain well protected from non-radiative processes..

March 22, 2017
11:00 am
Bldg. 440, A105-106

"Transport and Spectroscopy of Illuminated Molecular Junctions", Abraham Nitzan, University of Pennsylvania.  Host:  Tal Heilpern


The interaction of light with molecular conduction junction is attracting growing interest as a challenging experimental and theoretical problem on one hand, and because of its potential application as a characterization and control tool on the other. From both its scientific aspect and technological potential it stands at the interface of two important fields: molecular electronics and molecular plasmonics. I shall review the present state of the art of this field and our work on optical response, Raman scattering, temperature measurements, light generation and photovoltaics in such systems.

March 8, 2017
11:00 am
Bldg. 440, A105-106

"Harnessing and Avoiding Loss in Optical Metamaterials", Jason Valentine, Vanderbilt University.  Host:  Gary Wiederrecht


Optical metamaterials are man-made materials in which structuring is used to control the effective optical properties. Metamaterials have traditionally been made from metals and absorption loss has long been one of the primary impediments to their adoption in practical applications. Over the past several years researchers have come to realize that loss can not only be harnessed for certain applications but also completely avoided when transparency of the material is critical. In this talk, I will start by discussing how absorption loss in plasmonic materials can be utilized in energy conversion devices by harvesting hot electrons within the metal. In this case, the use of metamaterials provides the freedom to engineer the optical absorption while also optimizing the geometry of the metal for efficient capture of the hot electrons. In the second half of the talk I will discuss all-dielectric metasurfaces in which metal, and the accompanying absorption, is completely avoided. As with their plasmonic counterparts, manipulation of the unit cell structure of all-dielectric metasurfaces offers a means to engineer a wide variety of optical properties. This freedom, combined with the reduction in absorption loss, could lead to ultra-thin optical elements and assemblies. Along these lines, I will discuss several implementations of all-dielectric metasurfaces with functionalities that include polarization control, wavefront tailoring, near-unity reflection, and sharp Fano resonances.

February 22, 2017
11:00 am
Bldg. 440, A105-106

"Dimensionally Control of Complex Transition Metal Compounds", Turan Birol, University of Minnesota.  Host:  Kendra Letchworth-Weaver


The fact that the dimensionality of transition metal compounds’ crystal structures have a strong effect on their macroscopic properties is well known, but the microscopic mechanism by which this happens is not always obvious. First principles methods, such as Density Functional Theory or Dynamical Mean Field Theory, are capable of providing insight that can help uncover the mechanisms of dimensional reduction. In the first half of this talk, I will discuss the microscopic mechanism behind the emergence of novel polar phases in SrTiO3 Ruddlesden-Popper compounds, present results from first principles calculations, and clarify how the interfacial rumpling, only recently observed experimentally in these systems, is responsible of the dimensional reduction. The second half of the talk will be on low connectivity fluoroiridate compounds which, according to our Dynamical Mean Field Theory calculations, host a J=1/2 Mott insulator state because of the interesting interplay between the crystal structure, electronic correlations, and spin-orbit coupling.

February 8, 2017
11:00 am
Bldg. 440, A105-106

"Coherent Quantum Dynamics in Atomically Thin Semiconductors: Excitons, Trions, and Valley Pseudospins", Xiaoqin (Elaine) Li, University of Texas-Austin.  Host:  Jeff Guest


The near band-edge optical response of atomically thin transitional metal dichalcogenides  (TMDs) is dominated by tightly-bound excitons and charged excitons (i.e. trions). A fundamental property of these quasiparticles (excitons and trions) is dephasing time, which reflects irreversible quantum dissipation arising from system (excitons and trions) and bath (vacuum and other quasiparticles) interactions. Using a powerful coherent spectroscopy method known as the two-dimensional Fourier transform spectroscopy, we investigate the ultrafast coherent dynamics of excitons, trions, and valley pseudo-spins in these monolayer semiconductors. These experiments shine new light on the relevant time scales over which these quasiparticles and pseudospins can be coherently manipulated.

January 25, 2017
11:00 am
Bldg. 440, A105-106

"The Hidden Secrets of Nanocrystals, Interfaces, and Surfaces at Atomic Resolution", Christian Kisielowski, Berkeley National Laboratory.  Host:  Jianguo J.G. Wen


A suitable combination of single digit nanocrystals with their rich variety of tunable surfaces and interfaces allows tailoring materials with novel structure-function relationships. The design of new catalytic materials [1,2] may serve as examples. However, it remains challenging to characterize and understand such materials at the atomic scale with single atom sensitivity in 3D [4] because of their pronounced sensitivity to the probing electron radiation that unintentionally alters their pristine structure, often beyond recognition. We address this challenge by applying low dose-rate (< 10 e/Å2s) in-line holography [4], which combines the best imaging practices developed for biological research with the acquisition of image series. In essence, the new microscopy method exploits reversible object excitations by capturing focus series of entirely noise dominated images that are reconstructed to obtain electron exit wave functions of radiation sensitive matter with unprecedented contrast and resolution. We observe a variety of previously unknown atom configurations that are otherwise hidden behind a barrier of beam-induced object alterations and structures that are greatly affected by an exposure of the material to water vapor or other gases in environmental electron microscopy. Chemical compositions can be determined by contrast measurements alone and functional processes can be triggered and tracked in real time at atomic resolution.
[1] J. Yang, et al., Nature Materials (2016) DOI: 10.1038/NMAT4794
[2] Y.Yu, et al., Nano Letters (2016) DOI: 10.1021/acs.nanolett.6b03331
[3] F.R. Chen et al., Nature Commun. 7:10603 doi: 10.1038/ ncomms10603 (2016) 
[4] C. Kisielowski, Advanced Materials 27 (2015) 5838-5844

January 12, 2017
2:00 pm
Bldg. 440, A105-106

"Quantum Control Over Diamond Spins with a Mechanical Resonator", Greg Fuchs, Cornell University.  Host:  Stephen Gray

Creating and studying coherent interactions between disparate solid-state quantum systems is a challenge at the intersection of atomic physics, condensed matter physics, and engineering.  In general, different physical realizations of a quantum bit (qubit) operate at different frequencies, on different size scales, and couple to different fields. Nonetheless, efforts to create “hybrid quantum systems” are appealing because they could enable a quantum concert – were parts are played by different physical qubits that each offer the best performance in a particular area.  There is a growing consensus that mechanical motion is a “plastic” degree of freedom for solid-state qubits, with the potential to form a coherent interface between them, and with light.  This has motivated intense research into the coherent interactions between mechanical resonators and qubits formed from photons, trapped atoms, superconducting circuits, quantum dots, and nitrogen-vacancy (NV) centers in diamond, to name a few.  I will describe our experiments to coherently couple NV center spins to gigahertz-frequency mechanical resonators using crystal lattice strain.  In high-quality diamond mechanical resonators, we demonstrate coherent Rabi oscillations of NV center spins driven by mechanical motion instead of an oscillating magnetic field.  We also use the mechanical resonator to protect the coherence of the NV center spin.  Finally, I will describe recent results in which we experimentally examine the spin-strain coupling within the NV center excited-state manifold and explain how it can be used to cool a mechanical mode.