D. Aguilera et al.
Abstract:
AbstractThe theory of general relativity describes macroscopic phenomena driven by the influence of gravity while quantum mechanics brilliantly accounts for microscopic effects. Despite their tremendous individual success, a complete unification of fundamental interactions is missing and remains one of the most challenging and important quests in modern theoretical physics. The STE-QUEST satellite mission, proposed as a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), aims for testing general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by performing a test of the Universality of Free Fall of matter waves in the gravitational field of Earth comparing the trajectory of two Bose-Einstein condensates of 85Rb and 87Rb. The two ultracold atom clouds are monitored very precisely thanks to techniques of atom interferometry. This allows to reach down to an uncertainty in the Eötvös parameter of at least 2 · 10^−15. In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources.
"An ultra-bright atom laser" [New Journal of Physics 16, 033036 (2014)], was selected from Editors of New Journal of Physics as one of the three most important publications which were included in the exclusive collection "Highlights of 2014" of journal in the field of Atomic, molecular and optical Physics.
V. Bolpasi, N.K. Efremidis, M.J. Morrissey, P. Condylis, D. Sahagun, M. Baker and W. von Klitzing
New Journal of Physics 16 033036 2014
Abstract:
We present a novel, ultra-bright atom-laser and ultra-cold thermal atom beam. Using rf-radiation we strongly couple the magnetic hyperfine levels of 87Rb atoms in a trapped Bose-Einstein condensate. At low rf-frequencies the resulting trap opens up just below the condensate and a well collimated, extremely bright atom laser emerges from just below the condensate. As opposed to traditional atom lasers based on weak coupling, this technique allows us to outcouple atoms at an arbitrarily large rate. We demonstrate an increase in flux per atom in the BEC by a factor of sixteen compared to the brightest quasi-continuous atom laser. Furthermore, we produce by two orders of magnitude the coldest thermal atom beam to date (200 nK).
Supplementary Material:
- A grayscale version of Fig. 1. (link)
- The slices and fits used in the analysis of Fig.1c, i.e.the atom beam containing both a thermal beam and an atom laser beam. (link)
- A video of the numeric simulation of an atom laser. (link)
Research directions / Objectives
The research activities of the team are focused in the directions of Observational as well as Theoretical Astrophysics.
- Observational Astrophysics
The observational efforts of the group are based on data obtained with Skinakas Observatory, Space observatories (e.g. Chandra, XMM-Newton, Hubble Space Telescope, Spitzer Space Telescope, Herschel Space Telescope), and other major ground-based telescopes. The members of the team lead research programs in the following areas:
- X-ray emission from black holes (characterization of variability and spectra as indicators of black-hole mass and physical processes in accreting material).
- Multi-wavelength emission from accreting X-ray pulsars (connection between gas reservoir and accretion, interaction of pulsar magnetosphere and the accretion flow).
- X-ray emission from Anomalous X-ray pulsars (interpretation of their X-ray spectra in the context of accretion from a fall-back disk).
- Accreting binary populations in nearby galaxies (connection of accreting binaries and star-formation activity; the nature of Ultra-luminous X-ray sources; parameters influencing accreting binary formation and evolution).
- Mid-infrared properties of Luminous and Ultraluminous Infrared Galaxies (LIRGs/ULIRGs) (the nature of activity in the most luminous galaxies in the Universe).
- Star formation and stellar populations in Hickson Compact Groups.
- Multi-wavelength studies of interacting galaxies (the evolution of star-formation and nuclear activity along the merger sequence).
- Extragalactic large-scale jets (study of the polarization and the magnetic field structure in large scale jets emanating from accreting supermassive black holes).
- Interstellar magnetic fields (measurment of the interstellar magnetic field in our Galaxy by measuring the polarization of background sources).
- Detection of exoplanets (intensive monitoring with Skinakas of exoplanet candidates for the identification of exoplanets and measurements of their parameters).
- Theoretical Astrophysics
The theoretical efforts of the group are focused in the following areas:
- X-ray emission from accreting black-holes (modeling the physical processes in the accretion flow, and the resulting energy and Fourier spectra).
- Anomalous X-ray pulsars (modeling of the accretion flow onto X-ray pulsars; interpretation of observational results in the context of the fall-back disk model).
- Jets from accretion flows (emission mechanisms in astrophysical jets; spectrum, variability, and polarization of resulting emission).
- Dark matter (constraints on the nature of dark matter particles by modeling their high-energy signatures).
- Physical processes in star-formation.
- Modeling the Spectral Energy Distribution of Galaxies (deriving the physical connection between the interstellar medium and star formation in galaxies).
- Astrostatistics (Application of statistical methods in astrophysical problems).
The group is fundamentally interested in complex systems and applications. After making several contributions in the area of nonlinear metamaterials we focused on superconducting metamaterials were we brought about new properties such as left handedness, existence of breathers and chimeras and various other nonlinear modes. Currently our work is targeting the merging of complex systems with machine learning (ML) and attempts to produce meaningful and useful applications.
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Research directions / Objectives
The objectives are three fold, the following:
The study of low-dimension materials including C-based and Si-based materials as well as 2D-transition metal dichalcogenides (e.g. MoS2); their exploitation in nanoelectronics (especially in the form of nanoribbons, nanotubes and nanowires) and in the production and storage of green energy.
The study of magnetism of small metallic grains and their exploitation for producing advanced magnetic storage materials and new generation of sensors.
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Objectives:
The lab studies quantum materials, an umbrella of systems engaging atomic-scale building blocks, bearing strongly interacting elementary units (cf. charge carriers and electric/ magnetic moments) that give rise to collective phenomena, with remarkable physics (cf. quantum size-effects, spin liquids, superconductors, magnetoelectrics etc).
From size-controlled hybrid nanorystals to molecule-based materials, atomic structure insights enable the exploitation of selected crystalline solids for opportunities in innovative theranostics (e.g. image-guided therapeutics) or novel ways to supersede limitations in energy technologies (e.g. power transmission & use).
With the purpose to understand how the material's atoms are arranged and how their elementary units function, team members are encouraged to exploit our facilities in order to
- prepare/create solid-state compounds, for example, pertinent to mixed-valent transition metal oxides (chalcogenides or halides)
- measure basic physical properties, such as magnetic susceptibility, dielectric permittivity and electrical/thermal transport or optical activity
- correlate the macroscopic physical properties with the nanoscale rearrangements observed by synhcrotron X-ray and neutron scattering methods
- develop experimental tools involving external stimuli (e.g. pressure, magnetic field, laser light etc).
More elaborate experiments are done in collaboration with other research groups around the world. Strong links with theoretical teams assist our experimental efforts to choose the optimum set of materials and to justify our experimental findings.
Research Topics
Motivation:
Frustration arises when a system cannot minimize all the pair-wise interactions simultaneously because of local geometric constraints. Competing or frustrated interactions extend beyond the condensed matter physics and into biological materials, as for example, nature has the ability to "resolve" frustrated interactions in order to carry out some targeted biological activity.
Activity:
Frustration may give-rise to novel and complex phenomena that motivate us to (i) develop new class of materials, (ii) study cooperative phenomena in magnetism (e.g. magnetoelectric coupling) that provide fertile ground for testing theories of interacting systems that possess different spatial dimensions and sign of interactions that may impose local anisotropy of the basic interacting unit, the spin. Such fundamental studies can uncover mechanisms that benefit potential applications in low-power consumption devices and/or energy havesting technologies.
Literature:
Motivation:
Nanostructures with controlled size and shape, where magnetic and optical properties coexist, are most promising for innovative technologies (e.g. ranging from information storage to biomedical theranostics). Such a demand may be well-addressed when enhanced or collective magnetic/ photonic properties are established in nanoscale systems made of multiple subunits arranged in a controlled topological fashion through heteroepitaxial connections or self-assembled in secondary (e.g. cluster-like) structures.
Activity:
A major focus of our team entails the combination of chemistry and physics for the development of inorganic nanomaterials with potential in diverse applications. For this purpose, elaborate colloidal chemistry strategies are employed to control the nucleation and growth of nanocrystals (cf. zinc-blend, rock-salt, spinel, perovskite structural types) at moderate temperatures, while their multifunctional character is studied by bulk and local probe techniques. Moreover, directed-assembly of inorganic nanocrystals is chosen to provide a facile avenue to impart a collective nature in application-specific physical properties, offering the possibility for magnetically-driven image-guided diagnosis and therapy.
Literature:
Motivation:
Limitations of energy materials, and in particular for power transmission and storage, necessitates to decipher their workings at different length and time scales. In such an endeavor, cutting-edge tools are developed and implemented in real-word environments. Unique insights drawn in this way at the molecular or atomic level of matter, help understanding complex phenomena that are fundamentally important for discovering smart energy solutions. Amongst others, materials that could potentially transport electricity with zero resistance (cf. superconductivity) are the holy grail for improving dramatically the energy efficiency in electronics and power applications.
Activity:
It is our aim to identify structural rearrangements that accompany the different flow of electrons (i.e. from the charge reservoir to the conducting layer and vice-versa) in superconductors and the motion of charges in structurally related solid-state battery materials. Our activities devise alternative chemical pathways for single-phase model systems and based on them, attempt to parameterize the conditions leading to phases operating at elevated (critical) temperatures and/or offering the possibility to store higher energy density. The Lab strives to understand the physical or chemical interactions occurring on the atomic scale of intercalated layered transition metal chalcogenides / oxides. The outcomes contribute to clarifying the broader role of electronically-driven locally broken symmetries in triggering a phenomenon and creating useful physical properties.
Literature:
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We are exploring the interface between chemistry and physics of novel correlated electron systems and other bulk or nanoscale quantum materials that tackle energy-efficient technologies.
Activity:
In order to study different aspects of the structure, dynamics and functionality of new materials, the team engages:
- preparative solid-state chemistry & nanochemistry lab portfolios;
- various synthetic techniques including sol-gel and redox precipitation processes, in addition to conventional solid-state and colloidal chemistry high-temperature methods are been implemented. Nanocrystal functionalisation and bulk sample growth optimisations, with tools working at elevated temperatures (up to 1850 K), are available. There is great expertise in handling air-and moisture- sensitive compounds under anaerobic conditions, involving Schlenk lines and dry-box techniques.
- experimental stations for automated physical property measurements;
- materials bearing electronic phenomena and phase transitions, are tackled by a multimodal approach requiring strategic collaborations and appropriate development of in-house magnetic, dielectric, transport experimental and spectroscopic probes that are integrated in sophisticated sample environments, where applied electromagnetic stimuli can be flexibly utilized (e.g. low temperatures, high magnetic fields and elevated pressures).
- unique experimental tools (sought through peer-reviewed proposals) at European (ISIS-UK; PSI-Switzerland; ESRF-FR) and US (SNS-ORNL, NSLS-BNL) user-facilities of neutron, synchrotron X-ray and muon science.
Infrastructure Equipment
DC Magnetometer & AC Susceptometer, based on a MagLab-EXA 2000 multi-measurement system (Oxford Instruments) offers high resolving power in deciphering static and dynamic phenomena in low-moment, correlated electron systems of either bulk or nanoscale forms.
Applications:
Invaluable insights on the physical property materials response by measuring the moment versus applied magnetic field (e.g. hysteresis loops) or moment versus temperature, for deciphering static and dynamic phenomena associated with magnetic and superconducting materials. Its sensitivity is very high, therefore a small amount of sample is enough to ensure reliable signals. Automated measurements allow precise determination of the charasteristics of the superconducting state (e.g. crticial temperature, Meissner effect etc), as well as those of the Curie, Néel, and spin-glass states, including parameters such as the blocking or freezing temperatures of ferromagnetic, antiferromagnetic, superparamagnetic systems.
Specifications:
(a) High magnetic field (H= 0-7 Tesla), (b) Low-temperature liquid Helium cryostat (T= 1.8-350 K), (c) DC moment extraction (~10-4 emu), (d) AC susceptibility (~10-6 emu), f= 0.01-10 kHz, (e) samples of a few milligrams, can be accomodated in diverse morphologies, ranging from films and (nano)crystals to bulk forms – typical container, gelatin capsule ~15 mm long, with O.D. ~5 mm. The software measurement sequencer (open source) provides a set of high level actions to enable you to write and control measurements in a way that suit your own specific requirements.
The facility provides a modular experimental station to study the electrical characteristics of energy materials (e.g. electrode materials for Li/Na-ion rechargeble batteries), and beyond that the evolution of electric and magnetic dipole orders, as well as their degree of coupling, which is an identifying feature of a novel magneto-electric systems (e.g. sensors, high-capacity four-state logic memories etc.).
Applications:
This experimental station provides computer-controlled physical property measurements entailing a home-built modular sample environment offering to probe temperature (down to 2 K) and frequency (up to 2 MHz) dependent phenomena under externally applied electromagnetic stimuli (e.g. magentic fields up to 7 Tesla). It is equipped with custom-designed probes for mounting samples in various forms (e.g. polycrystalline pellet, single crystal, films), while the flexible integration of various types of digital measurement instruments allows automated data collection of physical quantities, including, Capacitance and Dielectric Loss, Voltage, Electric DC Current and Impedance etc.
Specifications:
Indicative capabilities include:
- low level sensitive measurements of current down to 10 aA (10 x10-18 A), electric polarization to charge levels down to 1 fC, very high resistance up to 210 PΩ (1018 Ω) and even I-V characteristics by a two-electrode configuration
- low noise voltage (down to 50 nV) measurements, characterization of low resistance/resistivity specimen by a standard four-wire setup (10 μΩ - 10 MΩ) and even Hall effects by Van der Pauw wiring
- impedance spectroscopy for precise measurement of capacitance and loss over a choice of frequencies, ranging from 50 Hz - 20 kHz, with a precision (AH 2700) bridge, and extended up to 2 MHz (with an option for DC-bias ±40 V), with an LCR meter (Agilent E4980A).
- continuous flow cryostat (T= 1.8-320 K)
- superconducting magnet (H= 0-7 Tesla)
The nanochemistry facility entails exploitation of elaborate colloidal chemistry approaches (ambient and high-temperature) to harness nanoscale size and shape-guiding mechanisms that afford various kinds of functional nanocrystals (single-phase, core@shell, anisotropic, hybrid particles) with tunable response (semiconducting, metallic, magnetic etc). Multidimensional nanostructures, such as cluster-like nanoarchitectures or periodic nanoparticle superlattices could also be realized by exploiting our know-how on directed assembly methods in liquid media.
Applications:
The aim is to provide a user-oriented platform for cost-efficient, easily scaled-up fabrication of novel inorganic nanoparticles, as well as their complete understanding that facilitates their use in diverse and interdisciplinary applications, from data storage and electronics to catalysis and biomedical imaging/therapy.
Basic Tools:
Projects benefit from controlled requirements for nanocrystal growth under anaerobic conditions met by the offered tools (e.g. Schlenk techniques, including digital temperature control growth conditions, Ar-circulating glove-boxes) that are combined with an armory of in-house characterization methods (structural, optical, electrical, dielectric, magnetic etc.).
- Chemical hoods equipped with vacuum-inert gas lines (Schlenk type), Glove-boxes, Centrifuges, Digital temperature controlled heating mantles, Magnetic stirrer hot plates, Incubators, Analytical balances
- Conventional and CCD-assisted stereoscopes, KBr hydraulic press, Glass-blowing propane torch
- Single and two-zone programmable furnaces (up to 1600°C) for vacuum or gas-flow reactions, High-vacuum line with portable programmable furnace for CVT (cf. sublimation & degassing), Thermogravimetric analysis
In everyday life generating and measuring temperature is straightforward, but in the quantum world, which reflects the behaviour of atoms, controlling the temperature is extremely more challenging. At very cold temperatures (cf. -269°C or near zero on the Kelvin temperature scale), as atoms are frozen, we can 'see' unique phenomena that would otherwise be masked by the thermal motion of atoms. As, complex materials are more likely to uncover their quantum properties at cold sample environments, low temperature refrigeration is an essential requirement.
Applications:
A tailored-made, small-scale facility that supplies liquid helium (He) for the needs of our variable-temperature physical property measurement equipment. Reaching temperatures of a few degrees Kelvin that is super cold with respect to ambient, employs artificial means, resting on a pumped helium system, built around a digitally controlled pulsed tube cryorefrigerator. With this technology, warm helium gas comes in contact with the Cold Head, where its thermal energy is absorbed into the 4 K (-269°C) heat exchanger. The process reduces the He-gas temperature, increasing its density, dropping it lower inside a condensing chamber; until it contacts the 4 K surface, where it condenses.The facility recycles the valuable helium gas that boils off from the liquid He dewars of the SQUID magentometer and the magento-electric workstation cryostat operating in our Lab.
Specifications:
The CRYOMECH PT410 re-liquefier is designed to recondense the boil off from liquid helium dewar/cryostats. As the boil off rates may vary depending on the type of temperature-dependent experiments being carried out, we have developed a peripheral medium-pressure vessel assembly, where the excess He gas is stored for future use. This gas is prone to contamination from impurities, like O2 and N2 species, which can reduce the efficiency of the re-liquefier. To this extent a custom-made, digitally-controlled He-gas purification system has been engineered to remove the impurities from the He-gas stream by means of chemical adsorption techniques. All in all, the facility is designed to return the liquid helium to the original dewar/cryostat, establishing a closed He loop, with an average liquefication rate of about 10 lt/day.
Simultaneous Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) based on a computer-controlled SDT Q600 TA-instruments apparatus.
Applications:
SDT Q600, is an analysis system capable of performing DSC and TGA at the same time, and as such it removes experimental and sampling variables in data analysis. The information provided differentiates endothermic and exothermic events, which have no associated weight change (e.g. melting and crystallization or even long-range magnetic order) from those which involve a weight change (e.g. degradation).
Specifications:
The SDT measures the heat flow and weight changes associated with transitions and reactions in materials, from ambient temperature and up to 1500°C. The system entails a physical property sensor (cf. thermocouple, balance), a controlled atmosphere (e.g. noble gas, O2/air) furnace and a temperature programmer, all interfaced to a computer, allowing for a bi-modal operation, namely:
TGA characterizes any material that exhibits weight loss or phase changes as a result of decomposition, dehydration, and oxidation. Two modes are commonly used for investigating thermal stability behavior in controlled atmospheres: (a) dynamic, in which the temperature is increased at a linear rate, and (b) isothermal, in which the temperature is kept constant.
DSC is acomplissed by employing a single heat source and two symmetrically located and identical sample platforms at the end of two parallel beams. Thermocouples, welded at the center of the sample platforms, measure the differential heat flow to the sample and reference as both are heated at a uniform rate by the furnace. Sample temperature is also monitored directly by the thermocouple in the sample platform. With proper calibration, the heat flow associated with endothermic and exothermic transitions in materials can be measured to a high degree of accuracy and precision (+ 2%). Without calibration, the heat flow results obtained are qualitative (DTA).
Sample-containing cup sizes
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alumina ceramic 40 µL, 90 µL (recommended for DSC-TGA studies)
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platinum 40 µL, 110 µL (recommended for TGA-DTA studies)
A preparative solid state chemistry laboratory is set up, where various synthetic techniques including sol-gel and redox precipitation processes, in addition to conventional solid-state high-temperature methods, are been implemented.
The materials straddle to a portfolio of transition metal oxides, mixed-metal chalcogenides, and all the way to hybrid perovksites.
In addition, intermetallic compounds can be grown with an arc-melting furnace (>2000 oC) equipped with a water-cooled copper hearth. The system is easily purged (vacuum & Ar-gas) allowing specimens of metal ingots to be rapidly formed with good purity.
Basic Tools:
- Glove-boxes for Air- and Moisture- Sensitive Compounds
- High Vacuum (P<10-4 mbar) or Helium-Flow Glass Line for Medium-Temperature (<1100 oC) for Solid-State Syntheses.
- High-Temperature Programmable Electric Furnaces (<1600 oC) for Solid-State Reactions.
- Chemical Vapor Transport Reactions (<1000 oC)
- Intercalation Reactions ("Soft Syntheses" at 40-80 oC).
- Solvo-/ Hydro- thermal Reactions (Teflon-lined Autoclaves: 23 mL, 250 oC, 1800 psi).
- Thermal Evaporator (Thick Film Growth: ~100 μm ).
Where necessary samples are flame sealed in evacuated glass or silica ampules and annealed at the required temperatures.
Distinctions
U.S. Grant Award (Fulbright Greece)
Fulbright Award (FORTH Research Highlights)
3rd Applied Research & Innovation Competition («Η ΕΛΛΑΔΑ ΚΑΙΝΟΤΟΜΕΙ»)
Chaire TOTAL de la Fondation Balard (Pôle Chimie Balard)
Outreach
Disorder in Magnetic Nanocrystals May Improve Cancer Treatment (BNL Feature Story)
Alexandros Lappas 2016-2017 Fulbright Visting Scholar (Greek Alumni Speak - Highlights Achivements)
Frustration in Two-dimensions (ESRF Scientific Highlights)
On-line lectures/ interviews
Tweaking Nanoscale Magnetism (E-MRS 2021 Spring Meeting, Symp-S - Invited Talk; credit IESL-FORTH)
Nanomaterials for Energy & Health Applications (ERT TV 'O3' - Interview; Greek language)
In the Battle Against Cancer (TV CRETA 'De Facto' - Interview; Greek language)
Broader Readership
Nanoscale Particle Organization & Photonics (credit IESL-FORTH)
Nanocrystals: Good Things in Small Packages (credit IESL-FORTH)
Lab website (early times)
Functional Nanocrystals and Quantum Magnetism Lab (External Website)
The Functional Polymer Nanostructures group aims at developing functional nanostructured materials, which possess specifically designed properties and tuning capabilities. The group focuses on understanding the relationship between microstructure-dynamics-properties of polymeric and hybrid materials, and on optimizing properties and designing novel advanced and functional materials.
The main activities include the investigation of: the morphology and dynamics of multi-constituent polymers (including polymer mixtures, block copolymers, homopolymer / copolymer mixtures, star and hyperbranched polymers) in bulk and in restricted geometries; the study of polymer surfaces, interfaces and thin films and the development of polymer coatings; the investigation of functional and responsive polymer materials and material surfaces; the study of polymer nanocomposites; the development of nanoparticulate catalysts for the chemical industry as well as the development of polymeric materials for applications in the field of energy. The investigation involves the design of the functional materials, the characterization of the structure, chain conformations and the dynamics in the melt, in solution and close to surfaces or under severe confinement as well as the study of the thermal, surface, mechanical, rheological, optical, optoelectronic and magnetic properties and their response to selected external stimuli. Such systems target specific applications ranging from every day commodity products, to greenhouse films in agriculture, to coatings-paints and adhesives for the automotive and aerospace industries as well as polymer electrolytes for batteries.
Research Topics
The Functional Polymer Nanostructures group aims at developing functional nanostructured materials, which possess specifically designed properties and tuning capabilities. The group focuses on understanding the relationship between microstructure-dynamics-properties of polymeric and hybrid materials, and on optimizing properties and designing novel advanced and functional materials.
The main activities include the investigation of: the morphology and dynamics of multi-constituent polymers (including polymer mixtures, block copolymers, homopolymer / copolymer mixtures, star and hyperbranched polymers) in bulk and in restricted geometries; the study of polymer surfaces, interfaces and thin films and the development of polymer coatings; the investigation of functional and responsive polymer materials and material surfaces; the study of polymer nanocomposites; the development of nanoparticulate catalysts for the chemical industry as well as the development of polymeric materials for applications in the field of energy. The investigation involves the design of the functional materials, the characterization of the structure, chain conformations and the dynamics in the melt, in solution and close to surfaces or under severe confinement as well as the study of the thermal, surface, mechanical, rheological, optical, optoelectronic and magnetic properties and their response to selected external stimuli. Such systems target specific applications ranging from every day commodity products, to greenhouse films in agriculture, to coatings-paints and adhesives for the automotive and aerospace industries as well as polymer electrolytes for batteries.
The Materials Synthesis Laboratory (MSL) has extensive experience on the synthesis, characterization and applications of polymeric and organic/inorganic hybrid materials, polymer colloids, “smart” stimuli-responsive materials, water-soluble/amphiphilic polymers, biologically active (co)polymers, supramolecular assemblies, micellar nanostructures, polyelectrolytes/polyampholytes, microgels/hydrogels and the modification of flat and curved surfaces. The group has extensive experience on “living” and controlled polymerization techniques such as, Group-Transfer Polymerization, Atom Transfer Radical Polymerization (ATRP) and Reversible Addition Fragmentation Chain-Transfer (RAFT), to prepare polymers of controlled macromolecular characteristics (i.e. molecular weight, and molecular weight distribution, composition and architecture). MSL is an internationally-renowned group in the field of multi-responsive and biocompatible/biodegradable polymers for biomedical applications such as targeted and controlled drug delivery, gene therapy and tissue engineering.
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Our mission, research focus and main scientific directions
We aim to understand the underlying mechanisms underpinning the behavior of soft materials by linking fundamentals (molecular interactions and conformations) to microscopic structure and dynamics (in two and three dimensions) and final material properties (mechanical, optical, interfacial). Our long-term goal is the molecular design of soft materials with tailored performance.
The rigorous study of the properties of soft materials involves devising protocols, using state-of-the art experimentation and developing specialized setups, as well as synergy of synthesis, specialized characterization, theory, simulations, and physical experiment (including access to specialized infrastructure). Examples of in-house instrumentation include evanescent wave dynamic light scattering, in-situ combination of rheometry with light scattering or microscopy, high-frequency rheometry and nonlinear rheometric tools.
The group’s strength lies on the experimental study of dynamics and rheology of well-characterized materials and determination of the physical origin of their response. Our ambition is to maintain and further enhance the Institute’s position as international pillar in soft matter research.
In this direction, we address outstanding problems in polymer and colloid physics, challenge theories, and open new directions. Current thematic directions (with main goals in parenthesis) are listed below:
- Associating polymers and networks (tailor mechanical reinforcement toward strong and deformable networks)
- Repulsive and attractive colloids (role of attractions in the flow of colloidal glasses)
- Colloidal gels (new routes to novel states, optimize processing conditions to tune properties)
- Anisotropic colloidal particles (rich state behavior and flow phenomena)
- Polymer topology (viscoelasticity, resistance to stretching due to interlocking, supersoft elastomers)
- Biomacromolecules and hydrogels (biological problems, protein solutions, mixed hydrogels)
- High pressure effects (phase behavior, dynamics, supramolecular polymers, industrial applications)
- Soft composites (tailor rheology and mechanics, bridge polymeric and colloidal behavior)
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The activity focuses on advanced materials and devices for energy, environment and electronic applications.
Research Topics
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An emerging activity focusing on exploration of quantum computing and hardware development that enables quantum technologies to be experimentally developed. Developed devices are based on polariton condensates, low dimensionality electronic quantum systems, spin waves and III-Nitride based qubits aiming at high temperature quantum information systems.
Research Topics
Quantum nanoelectronics technology comes into stage mainly to give an answer to the speed and energy consumption dilemma of semiconductor nanoelectronics. MRG is working towards an in-depth investigation of the most profound manifestation of the effects of quantum coherence on macroscale and the related quantum phenomena that hold the maximal potential to become emergent new generation electronics. The main objectives tackled are the following:
- Quantum transport in quasi 1D superconductors
- Relaxation of non-equilibrium quasi particle excitations in superconductors
- Size dependence of critical temperature of superconductors
This is a new activity for the group that was officially launched in early 2018 based on the excellence of the group in both the growth of state of the art compound semiconductor hetero (nano)structures as well as in the realization of novel nanodevices.
A future quantum technological era based on the manipulation of spin, quantum superposition, and coherence is foreseen to radically transform technology, science and society. MRG investigates integrated qubits towards room temperature computing. The focus is on the development of novel concepts based on III-nitrides quantum dots exploiting specific material properties such as large bandgap and relatively long high temperature decoherence time. In addition single electron transistor (SET) structures based on 2DEG and 2DHG heterostructures are investigated by fabricating demanding top-down plasma etching and by electrostatic isolation through top metal gates, employing aggressive e-beam lithography with device scaling projected down to 10nm. Finally MRG will study the roadmap for the integration of the GaN QD technology into the FDSOI process.
The future miniaturisation of electronic circuits following Moore’s law will require the introduction of increasingly disruptive technologies to limit power consumption and optimise performance per circuit area. Spin wave computing aspires to complement and eventually replace CMOS in future microelectronics. Spin wave computing has the potential for significant power and area reduction per computing throughput while reducing cost by alleviating lithography requirements.
MRG is partner in an EU FET type funded project (“CHIRON”) that started in April 2018. As a first step towards the vision of a full spin wave computer, CHIRON envisions hybrid spin wave–CMOS circuits that can be readily integrated alongside CMOS. CHIRON will fabricate basic logic gates, such as inverters and majority gates, demonstrate their operation, and assess their performance. As transducers between the CMOS and spin wave domains in hybrid circuits, CHIRON will develop magnetoelectric and multiferroic nanoresonators, based on nanoscale bulk acoustic resonators, which bear promise for high energy efficiency and large output signal. MRG develops FBAR type nanoresonators targeting membrane thickness below 50nm and operating frequency higher than 10GHz while investigating their performance with numerous magnetostrictive materials. In addition different RF device designs and materials approaches like highly strained or doped III-nitride layers will be investigated.
Quantum simulators promise to provide unprecedented insights into physical phenomena not accessible with classical computers and have the potential to enable radically new technologies. Analog dynamical quantum simulators constitute a most promising class of architectures to fulfil the ultimate promise to devise quantum machines outperforming classical computers. Here, we devise versatile and practical platforms for dynamical simulators – making use of polariton condensate lattices and assess their computational capabilities, to probe important questions in fundamental and applied physics, ranging from technology‐relevant problems, concerning transport processes or glassy dynamics, via long‐standing challenges in the physics of non‐equilibrium phenomena. Optical lattices have attracted much attention, since they can replicate phase transition between a BEC and a Mott‐insulating state in a Bose‐Hubbard model. By experimentally modifying physical parameters, such as the periodic potential amplitude, temperature, and density, it is possible to control relative strength between on‐site interaction and hopping amplitude at will exploring the phase diagram of such systems. Such experiments have been of particular interest in the quantum information community since the experiment realizes a nearly ideal quantum simulator.
The macroscopic nature of exciton‐polariton condensates provides ease of optical access and probing of individual lattice sites normally not achievable in cold‐atom systems. Furthermore, the non‐equilibrium nature of exciton‐polariton systems is particularly attractive, because it provides the ability to prepare and study out of equilibrium many‐body phases in a natural driven dissipative setting and the ability to probe these phases in situ using optical approaches. Our recent experiments show that individual trapped polariton condensates can exhibit spontaneous magnetization, and that the spins of pairs of trapped polariton condensate can be controllably aligned. This constitutes a key step towards using trapped polariton condensates for the realization of interacting bosons in a driven‐dissipative spinor Bose‐Hubbard model. Hence, a lattice of polariton condensates is expected to model a non‐equilibrium interacting spin system with unusual properties. It is against this background that the field of polaritonics has emerged and these exotic objects are not simply an academic curiosity – rather as we discuss below we will use them as the basis for quantum simulators.
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Infrastructure Equipment
M4C setup (home made with COTS):
- AC Hall setup (magnetic field and current modulation modes, μ
- min < 0.05 cm2/Vsec)
- AC Seebeck setup (thermal modulation mode)
- AC Nernst setup (magnetic and thermal modulation modes)
