Research Fields
Our group investigates nonequilibrium phenomena in chemical and condensed matter physics. We try to understand how strongly correlated quantum systems react to dissipative environments and to external perturbations, particularly in the context of the transport properties of nanosystems. This is a deeply challenging and fundamental problem, and we therefore work on state-of-the-art computational methods such as quantum Monte Carlo algorithms.
Haim Diamant studies theoretically the structure and dynamics of complex fluids and soft matter. These materials, such as suspensions, membranes, and biological fluids, are characterized by several length scales and time scales. The purpose of the research is to understand the physical principles underlying the structural organization of such materials and their response to various perturbations. Examples of recent and present research projects:
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Motion of particles in suspension within strongly confined spaces
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Motion of proteins embedded in a membrane
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Spatial and temporal response of biopolymer networks
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Patterns in fluid-supported thin elastic layers
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Alignment of particle orientations in suspension
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Our lab specializes in many areas of optical imaging and spectroscopy with emphasis on single molecule detection and development of imaging based techniques. Our research is focused on the application of novel imaging and optical detection approaches to genomic studies and biomarker detection. We are developing new spectroscopy and microscopy methodologies that combine advanced optics with tools and reagents from the realm of nano-technology. In addition, we have great interest in developing unique biochemistries for genomic analysis that are based on chemo-enzymatic reactions.
Research in the lab currently focuses on three fields of interest:
Single molecule genomics by optical mapping:
We create optical barcodes containing genetic and epigenetic information by labeling long chromosomal DNA molecules with fluorescent markers. Nano-fluidic channels are used to stretch the DNA by flow or electric field and the barcode is directly visualized by single molecule imaging. We are aiming to apply SR imaging techniques in order to increase the resolution and allow detection of genomic aberrations.
Epigenetic analysis technologies:
Epigenetics is one of the most exciting and fast growing fields in biology. It links biological signatures with mental or environmental conditions previously not believed to be quantified by physical means. We develop new methods for sequencing, targeted and global analysis of various epigenetgic markers. We use these novel methods in order to study epigenetic alterations related to disease. We are also very interested in the physiological interface between nature and nurture, biology and psychology, body and spirit.
High-throughput single molecule detection:
We develop optical methods and nano-biosensors for detection of rare analytes and weakly interacting biomolecules. Our emphasis is on ultrasensitive detection and quantification of clinical biomarkers. To achieve this aim we are developing a micro-lens-array based optical setup that can detect single molecule fluorescence from hundreds of confocal excitation volumes in parallel.
We are also active in development of single-molecule counting schemes and development of high resolution imaging techniques and specialized contrast agents that utilize fluorescence, plasmonics and energy transfer for super-resolution (SR) imaging.
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Attosecond Science (High Harmonic Generation, Photoelectron-Photoion Coincidence Spectroscopy)
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Extreme Nonlinear Optics
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Numerical tools: Time-dependent Schrodinger equation (TDSE) description of Atoms and Molecules interacting with Strong Electromagnetic Radiation
The motion of electrons inside and between atomic and molecular systems is at the heart of all phenomena in nature (except for nuclear processes). It is, among others, responsible for the photosynthesis of plants, the emission of light in LASERs, the transport of information in our nerves and the outcome of chemical reactions. In our group we study, image and control the electronic processes accompanying chemical reactions down to the atomic scale and their natural sub-femtoseconds to attosecond timescale (one femtosecond = 10-15 seconds, one attosecond = 10-3 femtoseconds)- a scientific discipline termed “attoChemistry”. We develop a machine (which we call “attoCamera”) capable of producing an ultrafast "movie" of real-time electronic evolution in molecules, with resolution of few attoseconds. The motivation for this effort is associated with both fundamental and applied science: understanding of the electronic evolution in molecules will enable future control scheme of chemical reactions to be developed, and would open exciting new prospects for many research fields, e.g. in material science, life science, basic energy science, ultrafast data storage in electrical and magnetic media, and more.
We use strong lasers producing short pulses of light (whose instantaneous power is 20-times larger than that of the Israel Electric Corporation production capacity) in order to steer and detach electrons inside and between atoms and molecules and by that image electronic orbitals, control electron evolution in chemical reaction, collide electrons and ions which lead to the emission of laser-like x-ray radiation, and more. The research uses state-of-the-art experimental and numerical methodologies from Physics and Optics, applied to the understanding of the very basic foundation of Chemistry.
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Coherent control of molecular angular distributions in 3D - alignment and orientation of molecules in the gas phase.
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Nonlinear optics in the terahertz and near-IR.
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Ultrafast molecular dynamics
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Coherent radiative decay of excited populations
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Non-intrusive, in-situ terahertz spectroscopy of battery cells (under INREP project).
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Laser induced alignment of macromolecules in liquid and the
Research in the Galperin group is focused on developing new methods and their application to studying dynamics in open quantum systems. Recent applications include areas of optoelectronics, non-adiabatic molecular dynamics, and quantum thermodynamics. Below I provide a short description of notable achievements for each direction.
1. Developing Green’s function-based methods
Traditional application of Green’s function method relies on utilization of diagrams. The latter results from the expansion of the system evolution operator employing a small parameter. In open systems, one has at least two characteristic energy scales to consider: the strength of intra-system interaction U and the strength of system-bath coupling G. The two possible limits, U/G<<1 and G/U<<1 employ, respectively, Feynman diagrams within the standard nonequilibrium Green’s function (NEGF) approach and hybridization expansion, usually within the pseudoparticle (PP) NEGF. For the latter case we developed an alternative – the Hubbard NEGF – which appears to be more accurate even at low orders of expansion. Finally, in the absence of a small parameter (U~G) or for strongly correlated systems, we develop a method based on a superperturbation theory.
2. Optoelectronics
The development of experimental techniques at the nanoscale made it possible to carry out spectroscopy experiments in single-molecule junctions, where light-matter interaction leads to the interdependence of different system responses (such as photon flux and electric current, noises, etc.). The field is a natural meeting point of at least two research communities: optical spectroscopy and quantum transport. We employ many-body flavors of the NEGF technique for the description of optoelectronic molecular devices.
3. Non-adiabatic molecular dynamics
Non-adiabatic molecular dynamics (NAMD) is a fundamental problem related to breakdown of the usual time scale separation between electron and nuclear dynamics. NAMD plays an important role in many processes in chemistry, photochemistry, spectroscopy, coherent control, and energy transfer. Theoretical descriptions of the dynamics often employ ad hoc formulations with accurate (well-controlled) approximations only available for simple models (usually relying on assumptions of linear coupling and weak electron-nuclear interactions). We employ Green’s function technique as a starting point for the derivation of schemes describing the NAMD while employing well-controlled approximations developed in the Green’s function literature.
4. Quantum thermodynamics
The construction of quantum molecular devices became a reality due to the advancement of experimental techniques at the nanoscale. In nanoscale devices, a molecule usually forms a covalent bond with contacts on at least one of its interfaces, which results in hybridization of molecular states with those of the contacts. Therefore, thermodynamic formulation of systems strongly coupled to their baths (i.e., situations where the energy of system-bath interaction cannot be disregarded) becomes a practical necessity. Contrary to the weakly coupled situation, thermodynamic formulations for strongly coupled systems are still in their infancy. Traditionally, the field utilizes density matrix as a tool to describe the system. We suggest that Green’s function techniques provide more flexible theoretical language. Sometimes, this makes a difference of convenience in formulation; in other situations, the language may lead to conceptual advancements.
Structural chemistry, biology and virology studied by solid-state nuclear magnetic resonance.
Nuclear magnetic resonance (NMR) is a spectroscopic method that relies on the nuclear Zeeman splitting in a magnetic field. It provides detailed information on the chemical environment, structure, and dynamics of molecules.
We use solid-state NMR to study in atomic resolution the structures of various systems from small inorganic molecules to proteins and intact viruses.
Special emphasis is given to (1) Metaloenzymes and molecules related to psychiatric illness, the therapeutic mode of action of the lithium salt drug; (2) Viral structure and morphogenesis, including the structural impact of mutations, and the mode of genome protection; (3) protein-DNA interaction, large DNA structures; (4) The development of new methods, and new analysis methods to study proteins, enzymes, and metal complexes. The methods rely on quantum mechanics away from equilibrium and numerical simulations, and are examined and verified by experiments.
The lab work is multidisciplinary and requires the expertise in various fields: The expression, purification, and biophysical characterization of proteins and viruses; NMR experiments (we have two magnets in the school of chemistry suitable for solid-state NMR), computer-based spectral analysis and automation.
My major research activities are focused on synthesis, characterization of materials and study of ion-transport phenomena in new nanostructured electrodes and solid electrolytes for energy-storage devices.
The microelectronics industry is continually reducing the size of its products in order to produce small devices such as medical implants, microsensors, self-powered integrated circuits or microelectromechanical systems. Such devices need rechargeable microbatteries with dimensions on the scale of 1–10mm3, high energy density and high power capability. 3D concentric on-Si-chip architecture developed by our group, enables the fabrication of a network of 10,000-30,000 microbattery units connected in parallel that minimizes the ion-path length between the electrodes and provides high capacity per footprint area. This is achieved by the insertion of four consecutive thin-film-battery layers in the high-aspect-ratio microchannels (40-50µm diameter, 500µm depth) of the perforated chip. We have recently developed an inexpensive and simple electrodeposition method for the preparation of nanosize molybdenum oxysulfide and copper sulfide cathodes. An electrophoretic deposition (EPD) method for the preparation of thin-film LiFePO4 cathodes has been developed for the first time. My current research exploits a new approach for the preparation of ordered solid electrolytes by electrophoretic deposition. I am also interested in the combined effect of EPD and a homogeneous/gradient magnetic field. Within the framework of this research, different solvents and surface-active agents are tested for achieving well dispersed nanoparticles in stable suspensions. Such systems are controlled by the complex interplay of concomitant phenomena, including micellization, association of the surfactant with the polymer and adsorption of the surfactant on the species. Of particular interest is the effect of these cooperative interactions on the structure and ion-transport properties of polymer electrolytes confined in the pores of ceramics. 3D-tomography (to be carried out in collaboration with Imperial College, London) will provide the data sets for the calculation of the tortuosity factor at sub-100nm resolution. To produce core-shell and multiphase ceramic/alkali-metal salt nanoparticles, the method of EPD mechanochemistry is used.
Very recent subjects under investigation include the development and study of redox processes in high-energy-density all-solid-state lithiated Si/S battery and adsorption phenomena in supercapacitors based on porous silicon nanowires.
- Machine learning and Physical Chemistry. Prediction of dynamical properties of quantum materials using neural networks: Diffusion, spectroscopy and reaction rates.
- Developing new methods to describe quantum effects in classical simulations: Path integral molecular dynamics for indistinguishable particles.
- Simulations of chemical processes on water surfaces with applications to atmospheric chemistry and hydrogen storage in clathrate hydrates.
Our research follows two main directions: 1. Developing simulation methods for describing chemical and physical phenomena that are inadequately described using available models. 2. Applying these new tools and others to solve fascinating problems at the interface of chemistry and physics.
The main tool is molecular dynamics (MD) simulations, a “virtual microscope” that allows following the classical dynamics of individual atoms in time and investigating chemical and physical processes for large systems (liquids and solids). However, MD simulation are inapplicable at low temperatures or for quantum materials, whose properties are determined from the quantum correlations between their constituent particles. Unfortunately, solving the quantum equations of motion is impossible for large systems.
To overcome this important problem, we develop path Integral MD simulations (PIMD) which allow describing the thermodynamic properties of quantum condensed phase systems while being computationally efficient. We aim to solve two limitations of PIMD simulations that will greatly extend their applicability:
- Using neural networks to obtain dynamical properties of quantum systems e.g., diffusivity, reaction rates and spectroscopy. We will apply this approach to hydrogen storage in ice-like cages (clathrate hydrates), promising renewable energy materials. Since hydrogen is the lightest element and since clathrate hydrates are formed at low temperatures, quantum effects cannot be neglected.
- PIMD simulations for bosons and fermions. This development would allow applications to systems of ultracold trapped atoms which exhibit fascinating phenomena, such as Bose-Einstein condensation, and can potentially be used in emerging quantum technologies.
The research in Prof. Hod's group focuses on computational nano materials science. As part of his work he studies the electronic, magnetic, mechanical, and electro-mechanical properties of materials at the nanoscale. Using advanced computational platforms his group studies many physical phenomena including electron dynamics in open quantum systems, quantum interference and coherent phenomena in circular molecular junctions, friction at nanoscale interfaces between layered materials and chemisorption on various surfaces including graphene, nanodiamonds, and nanotubes of silicon and boron-nitride.
Prof. Hod's research interests merge curiosity driven and applied science. The applicational potential of his research encompasses a wide range of technological areas including the world of molecular electronics and spintronics, nanotribology – a field that advances the development of solid lubricants based on layered nano-particles, ultra-sensitive chemical detectors, and nano-electro-mechanical devices for navigation and control purposes.
The group uses a variety of computational methods of varying levels of complexity according to the problem at hand. The span of tools available to the group members includes advanced quantum computational models based on density functional theory, classical molecular dynamics simulations, and simplified phenomenological models that provide physical intuition on the studied systems. A combination of codes developed within the group along with commercial computational chemistry packages, operating on a highly parallelizable high-performance computer cluster, allows us to address a wide range of problems in the fields of chemistry, physics, and material's science at the nanoscale.
Development of advanced methods in magnetic resonance spectroscopy for characterization of surface-bound species.
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Dynamic Nuclear Polarization
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High-field Electron Paramagnetic Resonance
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Implementation of EPR and DNP techniques for atomic-level characterization of single atom catalysts
Nuclear Magnetic Resonance (NMR) spectroscopy is the best spectroscopic method for obtaining structural information on the atomic level. The main limitation of NMR, which prevents it from being equally successfully applied as a surface analysis tool, is its limited sensitivity. Dynamic Nuclear Polarization (DNP) is a method to boost the NMR signal by orders of magnitude and thus enable the use of NMR also for analysis of rare species such as those attached to the surface.
The Electron Paramagnetic Resonance (EPR) spectroscopy allows for structural characterization of paramagnetic species such as free radicals and transition metal complexes. Traditionally the EPR measurement is performed at low magnetic field which limits the amount of information that can be obtained. Development of high-field EPR methodology will allow for better understanding of the underlying mechanisms of DNP and obtaining high-resolution structural information on paramagnetic transition metal complexes on a surface.
The developed methods will be used to obtain structural information of surface-localized transition metal complexes such as those in single atom catalysts (SAC). The methodological developments will allow for a better understanding of the catalytic mechanisms of SACs which in turn will enable the rational development of the next generation of catalysts with improved properties.
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Preparation of inorganic, colloidal nanocrystals and studies of their physical properties – noble metals, magnetic metals, various types of oxides, semiconductors
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Sudies of magnetization dynamics and spin polarized transport in arrays of magnetic nanoparticles
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Development of transparent electrodes based on metal nanowires, produced by a wet chemical method
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Studies of nanoscale ferroelectricity
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Studies of chiroptical effects in inorganic nanocrystals interacting with chiral molecules and enantiomeric and shape control in the growth of nanocrystals with chiral crystal structure
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Novel Nano materials synthesis (Nanowires) in advanced methods in solid/liquid/gas states and Chemo Physical characterization
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Synthesis of “Intelligent” Nano materials with optical, electrical and magnetic controlled properties
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Development and construction of electronic Nano devices for sensing of Chemical and Biological spices
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Development of Nano Pillars for monitoring of In-cell parameters
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Development of Nano devices for monitoring for Neuros activities and signals
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Sensing of Biomarkers and Metabolites
Our group is broadly interested in complex systems that are governed by statistical laws and random events. We conduct research at the interface of Physics, Chemistry, Biology, Probability and Statistics; and aim to cut across traditional disciplinary boundaries in attempt to mathematically describe, explain, predict, and understand natural phenomena.
We are interested in studying the underlying physical processes that govern the mechanics, self-organization, dynamics, and statistics of complex fluids out of thermal equilibrium. Our belief is that by studying in detail many such driven systems we will be able to observe emergent shared characteristics, paving the way for a theoretical description.
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We use holographic optical tweezers to manipulate and drive microscopic objects, a variety of optical microscopy techniques to image these objects, and image analysis to study their motion and morphology.
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We study the motion of small collections of bristle robots, the interactions between them as mediated by the environment and their collective behavior under minimal intervention. One of the applications we are interested in is to harness these small ensembles of simple robots to do complicated tasks in a robust and flexible way. For example, we would like to have them transport cargo through an obstacle filled path, much like ant swarms.
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We are interested in studying the motion of single proteins in live cells. To this end we collaborate with many labs across the country. Currently, we are collaborating with a researcher in the Faculty of Medicine to uncover the mechanisms by which transcription factors search and find regulatory sites in the context of higher order chromatin organization in living cells during neural differentiation.
In nature, light and matter are constantly interacting – photons are absorbed or emitted, they induce chemical reactions and drive the transport of charges. When such interactions occur inside a wavelength-scale region confined by a photonic nanostructure they can dramatically change, giving rise to new and exciting effects. In our research we explore artificial structures with which we may achieve complex materials with new properties and control the interaction of light and matter. We focus on several aspects of this theme, which lie at meeting point of chemistry, quantum physics optics and material science:
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Strong interaction of molecules with light - we investigate the optical properties of organic molecules (dyes) coupled to optical devices, aiming toward understanding quantum many-body processes in such hybrid systems and controlling these interactions. Gaining such control is important for photo-chemistry, light-harvesting and organic light-emitting devices.
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Optical properties of metallic nanoparticle-clusters - A nanometer-size gold particle has a very distinct color, completely different than the color of bulk gold. The reason is that when we shape a metal over a nanometric scale it supports localized plasmon modes that depend on details such as geometry and size. In our research we explore the assembly of such nanoparticles into well-defined clusters in order to achieve composite materials with new optical properties.
Electronic transport through molecular wires and junctions has been attracting much attention due to remarkable experimental and theoretical advances. The research is motivated by the possibility to further explore the quantum realm as well as by possible magnificent technological breakthroughs. Considering the time scale of molecular processes, molecular junctions can be envisioned to be fast electronic components, operating in the sub pico-second range, i.e., three orders of magnitude faster than current technology. Albeit impressive advancement in understanding the steady state transport properties of these junctions, their time dependent transport characteristics remain unexplored. We develop experimental methods to probe the dynamic properties of junctions. The devised methods are essentially new tools to probe molecular dynamics at interfaces under non-equilibrium conditions.
Programmable materials are materials whose properties, behavior, and functionality are directly dictated by the chemical information that is written and programmed in them. The prime example of such materials are proteins, in which the programming of the amino acid sequence (the primary structure) directly determines the three-dimensional structure (the tertiary structure).
Our group studies chemically programmable materials that contain a sequence of commands (information) for performing a specific task or function coded in their chemical structure. In particular, we are interested in synthesis and fabrication of polymer fibers that can hold chemical and physical information, and study how can this information be used for folding these one-dimensional fibers into three-dimensional structures, and how can a specific design lead to selective binding and to self-assembly. Using tools from thermodynamic and from Information Theory, we explore the underlying principles that determine the behavior of programmable materials. We also study the use of such materials for fabrication of microelectromechanical systems (MEMs) and for medical applications including tissue engineering and smart drugs release mechanisms.
In our lab, we employ a variety of fabrication techniques including lithography, electrohydrodynamic co-jetting, and deposition methods. In addition, we make use an array of microscopy and spectroscopy techniques for characterization and manipulation of these systems, and utilize a variety of computational and theoretical tools for modeling, analysis, and understanding the characteristics of such materials.
We are interested in life processes that involve deformation and remodeling of membranes, such as viral infection, cell-cell fusion in fertilization, and secretion of neurotransmitters by exocytosis. In order to gain insight into membrane remodeling in such processes, we use mechanical single-molecule techniques: Optical Tweezers in combination with confocal fluorescence microscopy and Atomic Force Microscopy (AFM). These tools allow us to measure membrane mechanical properties and to explore the interactions between membranes and proteins in bio-mimetic model systems and cells. By such quantitative measurements we hope to contribute to the understanding of biological processes in which membrane remodeling plays a central role.
Further reading
