08:30 | Registration |
09:00 | Leslie Schoop, Princeton University
Synthesizing the metastable: soft chemistry for new quantum materials
Conventional solid-state synthesis produces thermodynamically stable compounds, yet many of the most interesting electronic states occur in metastable phases. Organic chemists routinely make kinetic products by controlling which bonds are made and broken, and we apply the same idea to extended solids through soft-chemical, topotactic reactions at or near room temperature. I will discuss two examples. In the first, electrochemical oxidation removes a small fraction of the lead from the linear-chain compound Au2PbP2. The lead vacancies order, the gold chains distort, and the crystal loses its inversion center, turning a centrosymmetric metal into a polar metal that becomes superconducting at 1.5 K. A second-order Jahn-Teller picture explains why the structure distorts once electrons are removed. In the second example, we intercalate neutral amine molecules between the layers of 1T′-WS2, a metastable polymorph whose monolayer is predicted to be a two-dimensional topological insulator. The molecules push the layers apart until they are electronically decoupled, so that a bulk crystal behaves like a stack of isolated monolayers, and chiral amines transfer their chirality to the inorganic host. Together, these examples show how chemical control over bonding opens routes to quantum materials that high-temperature synthesis cannot reach. |
09:35 | Armi Tiihonen, Chalmers University of Technology
Accelerated materials research for robust perovskite solar cells
Perovskite solar cells are a promising photovoltaic technology that can achieve high efficiencies in energy conversion but tends to be prone to degradation over time. I will discuss how machine learning and laboratory automation can help to accelerate the stability research of perovskite solar cells, as well as materials screening for technology development. |
10:10 | Sinéad Griffin, Lawrence Berkeley National Lab
Beyond Boring Bulk Symmetry: Emergent Spin Splitting, Experimental Signatures, and Collective Excitations
The huge surge of interest in so-called ‘altermagnets’ has been driven by the observation that one can achieve spin splitting in compensated antiferromagnets, even in the absence of spin–orbit coupling. This has led to a comprehensive classification scheme for non-relativistic spin splitting (NRSS), describing how the crystallographic symmetry operations linking opposite-spin motifs determine momentum-space structures with well-defined symmetries. However, even in bulk crystals, NRSS can manifest outside the well-defined altermagnetic classes. Here I will discuss our recent efforts to explore the minimal requirements for NRSS, how these extend beyond bulk crystalline materials, and how they manifest in transport and collective excitations. Rather than asking for the specific conditions that cause altermagnetism, we instead ask under what conditions NRSS is prevented. I will show how spatial textures such as domain walls and structural twin boundaries can remove degeneracy-protecting symmetries, creating electronic states that do not exist in the parent bulk material. I will then discuss how retaining the internal orbital and multipolar structure of spin density extends this description to magnetic dynamics beyond conventional Heisenberg models. Our goal is a framework connecting microscopic symmetry breaking to the realization, dynamics, and detection of NRSS well beyond conventional bulk classifications. |
10:45 | Coffee break |
11:05 | Sibylle Bauer, SIPRI
workshop |
11:40 | Lunch |
12:45 | Michael Mayer, Adolphe Merkle Institute, University of Fribourg
TBA |
13:20 | Nako Nakatsuka, EPFL
Aptamer-Based Nanotechnologies for Monitoring Brain Chemistry
Monitoring small molecules is essential for advancing diagnostics, therapeutics, and real-time health monitoring across a wide range of biomedical applications. Specifically in neuroscience, advancing our fundamental understanding of brain (dys)function requires the development of novel nanotools capable of monitoring chemical signaling in complex biological systems. Detecting small molecules in the brain is challenging due to low concentrations, limited mass and charge, and interference from high amounts of nonspecific molecules. Neurotransmitters co-exist with structurally similar metabolites across different brain regions. At the CHEMINA Lab, we tackle this challenge by integrating DNA-based recognition elements called aptamers, into nanoscale biosensing platforms. Aptamers are systematically designed oligonucleotide receptors that are engineered for selective target recognition. We harness aptamers designed to recognize small-molecule neurotransmitters such as serotonin and dopamine. We have developed nanoscale aptamer-modified nanopipettes with ~10 nm openings – approaching the spatial resolution of synapses where neurons communicate (~50 nm) – as well as microscale aptamer-functionalized field-effect transistors. Reversible target binding induces conformational changes in the aptamers, rearranging their negatively charged backbone, which are transduced into measurable electrical signals through the nanopore or across the semiconducting channel, respectively. Extensive characterization of these target-specific aptamer structural dynamics has provided fundamental insights into the signal transduction mechanisms underpinning our biosensing technologies. These findings lay the foundation for expanding this approach to a broad range of small-molecule targets – including sugars, amino acids, lipids, and hormones – relevant to diverse areas of human health. |
13:55 | Coffee break |
14:15 | Tomas Jungwirth, Czech Academy of Sciences and University of Nottingham
Route to the identification and observation of altermagnetism
The replacement of Flash memories by spintronic memories on advanced-node microprocessors has made ferromagnets vital complements of semiconductors in present chip industry. The basic physical principal underpinning spintronic functionalities is the time-reversal symmetry breaking. In ferromagnets, it takes the form of lifted Kramers degeneracy of the Fermi surface into majority-spin and minority-spin electronic states, giving rise to internal magnetization. Since magnetization limits scalability due to associated stray fields, and hinders energetically inexpensive transition from GHz to THz operation speeds, a new route of research emerged towards spintronics without magnetization. In the talk we first show how this route was opened by the realization that spin degeneracy does not necessarily exclude breaking of the time-reversal symmetry in Fermi surfaces of some seemingly ordinary collinear antiferromagnets. This led to the demonstration of experimental spintronic memories with no stray fields and switching times scaled down to picoseconds. Despite the progress, the absence of spin splitting is a major roadblock which is circumvented only at the expense of subtle relativistic effects used to operate these antiferromagnetic devices. Instead of circumventing, we will remove the roadblock in the second part of the talk by presenting theoretical description and experimental demonstration of altermagnetism, and of spintronic devices based on this recently identified distinct form of magnetic order. A spin-resolved and angle-resolved photoemission spectroscopy directly evidences that the electronic band structure of altermagnets breaks the time-reversal symmetry by spin-splitting the electronic states, despite the absence of magnetization. This enables to operate the magnetization-free altermagnetic devices by analogous means to those used in ferromagnetic spintronics, as also already demonstrated in initial experiments. Besides magnetism and spintronics, altermagnets open new research directions across many fields of condensed-matter physics, including superconductivity or topological quantum matter. |
14:50 | Caroline A Ross, Massachusetts Institute of Technology
Complex Oxide Polymorphs for Spintronic, Magnonic and Photonic Technology
Ferrimagnetic garnets offer a wide range of useful properties for magnetic technology including low damping, tunable magnetization and compensation, and magneto-optical activity, but it has proved difficult to control their behavior with an electric field. To address this, we use epitaxy to grow magnetoelectric composites consisting of garnet coupled to a ferroelectric oxide. By pre-patterning regions of a thin perovskite seed layer onto a garnet substrate and subsequently depositing a film, we create multifunctional composites consisting of garnet and perovskite regions of 50 nm and above with the same composition but dramatically different structures and properties, designated as laterally differentiated polymorphs (LDPs). We demonstrate magnetoelectric coupling in LDPs with compositions Bi2.25Y0.75Fe5O12 and Bi3Fe5O12 in which an electric field applied to the ferroelectric perovskite phase modulates the magnon modes and the magnetooptical hysteresis loop of the ferrimagnetic garnet. LDPs expand the portfolio of functional oxide nanocomposites formed by self-assembly, and unleash the potential of garnets for voltage-controlled spintronic, magnonic, and photonic devices. |
15:25 | Break |
15:40 | Steve Chu, Stanford university
How does biology work in a molecular environment dominated by thermal fluctuations and dissipation work
The development of very bright single particle probes has revolutionized biological research. A summary of our development of two types of new bright optical probes will be given. Rare earth nanoparticles allowed us to study the molecular motor dynein in vitro and in live neurons with 4 nanometer and 1 millisecond temporal and spatial resolution for many minutes. More recently, the resolution has been improved to 1 microsecond time resolution and 0.1 nm spatial resolution. One goal of this work is to test a hypothesis of how dynein uses exploits thermal fluctuations to move molecular cargos. We are also using protein folding technology to attach organic dyes to targeted proteins with small chains of amino acids to create bright molecular-sized optical probes. |
16:15 | Ben Feringa, University of Groningen
The Art of Building Small: From Molecular Switches to Motors
The fascinating molecular motors and machines that sustain life offer a great source of inspiration to the molecular explorer at the nanoscale. Among the major challenges ahead in the design of complex artificial molecular systems and is the control over dynamic properties and responsive far-from-equilibrium behavior. Chemical systems and adaptive materials ultimately require integration of structure, organization and function of multi-component dynamic molecular assemblies at different hierarchical levels. A major goal is to achieve and exploit translational and rotary motion. In this presentation the focus is on the dynamics of functional molecular systems and machines as well as triggering and assembly processes. We design switches and motors in which molecular motion is coupled to specific functions. Responsive behavior will also be illustrated in self-assembly and responsive materials with a focus on cooperative action, amplification along multiple length scales and 2D and 3D organized systems. The design, synthesis and functioning of rotary molecular motors and machines will be presented with a prospect toward future dynamic molecular systems and materials |
