Paper by Warburton Group on MoS₂ Published

On the 8th, Physical Review Letters published work on optical measurements of the monolayer semiconductor MoS₂ by former Ph.D. student in the Warburton group, Dr. Nadine Liesgang. The manuscript presents evidence for a spin polarized state of the mobile electrons. From our group, former Ph.D. student Hinrich Mattiat and current Ph.D. student Lukas Schneider collaborated on the project, especially in the fabrication of devices and assisting in optical measurements. The work is entitled, Exchange Energy of the Ferromagnetic Electronic Ground State in a Monolayer Semiconductor.

Floris Attends Second Kick-off Meeting

From the 19th to the 21st, research scientist Dr. Floris Braakman represented the group at the kick-off meeting for our second new EuraMet collaborative project, entitled, “Quantum Anomalous Hall Effect materials and Devices for Metrology (QuAHMET)”. The meeting took place in Prague, Czech Republic and included two days of presentations and discussions.

The Quantum Hall effect (QHE) is the foundation for the realization of the primary resistance standard (PRS) in electrical metrology. QHE devices currently require low temperatures and high magnetic fields, impeding their adoption beyond national metrology institutes. The Quantum Anomalous Hall effect (QAHE) provides an opportunity to overcome these limitations while maintaining the unsurpassed accuracy expected of PRS. Greater knowledge of QAHE devices is essential to accelerate the development of a ‘quantum electrical metrology toolbox’ for the universal adoption of quantum electrical SI standards. This project aims to grow, characterize, and evaluate thin films for QAHE devices, leading to a detailed metrological assessment from sub-K to above 1 K, currents from below 100 nA to above 1 µA and over a wide range of external magnetic fields up to several Tesla. Our group’s role in the project is to characterize samples using scanning SQUID and scanning microwave microscopy.

Luca Forrer Speaks at SPIN Annual Meeting

From the 12st to the 14th, Ph.D. student Luca Forrer attended the 4th Annual Meeting of the NCCR SPIN in Pontresina, Switzerland. On the afternoon of Friday the 14th, he gave a talk entitled, “Scanning multi-gate and quantum dot microscopy”.

Prof. Poggio in Finland

From the 10th to June 13th, Prof. Poggio attended the MQSens Workshop on “Quantum sensing with nonclassical mechanical oscillators” near Helsinki, Finland. The aim of the workshop was to bring together experts and young researchers from the fields of quantum sensing and opto-/electromechanics in order to explore how quantum protocols can be adapted to mechanical sensors in the quantum regime for various applications. The conference was held at the Hotel Nuuksio and was chaired by Prof. Mika Sillanpää (Aalto University). Prof. Poggio gave a talk on the 13th entitled, “Using nanomechanics to study nanomagnetism”.

Floris at MetSuperQ Kick-off

On the 6th and 7th, Dr. Floris Braakman represented the group at the kick-off meeting for our new EuraMet collaborative project entitled, “Metrology for superconducting qubits (MetSuperQ)”. The meeting was held at the PTB in Braunschweig, Germany.

The project aims to address challenges in optimizing qubit coherence reproducibility, stability, control and readout in superconducting circuits for quantum computing. For this task, a new generation of metrological methods and tools will be needed. This project will develop such a suite of tools for superconducting qubits and apply them to state-of-the-art one- and two-qubit circuits. These new tools will underpin further engineering advances and allow for accurate characterisation of qubits and materials, as well as manipulation and read-out. Our group will contribute with scanning probe methods, including scanning SQUID microscopy.

Lukas at Quantum Sensing Conference in Paris

From the 4thto the 6th, Ph.D. student Lukas Schneider attended the International Conference on “Quantum Sensing” at the Collège de France in Paris, France. The conference aimed to bring together two scientific communities: the one focusing on fundamental aspects of the quantum phenomena in superconducting hybrids and the other working on the development of quantum devices and detectors, pushing the frontiers of their sensitivity and their range of applications, inventing new technological and conceptual routes. Lukas presented a poster on his latest nanowire-based magnetic force microscopy work.

Group Members at Attocube 2D Materials Conference

From the 3rd to the 8th, Ph.D. students Daniel Jetter and Andriani Vervelaki attended the 2D Materials Conference outside of Munich in Haar, Germany. The conference was organized by Attocube AG and included an impressive roster of invited speakers presenting the latest results in this fast-moving field. Andriani presented a poster on teh 6th entitled, “Controlling magnetic domain evolution via strain in CrSBr”. After completing his duties as host of the Swiss Nanoconvention, Prof. Poggio joined the conference on the 6th and gave an invited talk on the 7th entitled, “Scanning SQUID-on-tip microscopy of 2D and chiral magnetism”.

Swiss Nanoconvention in Basel

The Swiss Nanoscience Institute (SNI), of which Prof. Poggio is the director, hosted the 2024 edition of the Swiss Nanoconvention at the Basel Convention Center from the 4th to the 5th. A list of internationally reknowned speakers presented their latest results from the various corners of nanoscience, including materials physics, nanomedicine, and chemistry. From physics, highlights included keynote speakers Prof. Kam Moler (Stanford), Prof. Simon Gröblacher (Delft), and former director Prof. Christian Schönenberger, as well as sessions on quantum materials, 2D materials, optomechanics. Thanks to the SNI management team (especially Kerstin Bayer-Hans) for a wonderful job organizing this successful meeting!

Group Trip to Ligerz

From the 31st to June 2nd, 9 group members travelled to Ligerz, Switzerland for a relaxing group weekend at the Aarbergerhus. Ligerz is a small village on the shore of Lake Biel in the Canton of Bern. Despite the rainy weather forecast, Saturday proved to be a perfect day allowing for hiking to the Twannbachschlucht and a short boat trip and hike around St. Peterinsel. Thanks to Ph.D. student Luca Forrer for the organization and all for the good times!

Roadmap on Nanoscale Magnetic Resonance Imaging Published

On the 14th, Nanotechnology published a ‘roadmap’ article nanoscale magnetic resonance imaging (NanoMRI). The work is entitled, Roadmap on nanoscale magnetic resonance imaging. It reports on the current state of the art in NanoMRI technologies, it outlines the areas where they are poised to have impact, it identifies the challenges that lie ahead, and it proposes methods to meet these challenges. Prof. Raffi Budakian (Waterloo) led the team putting together the article, which included Prof. Amit Finkler (Weizmann) and Prof. Alex Eichler (ETHZ). Prof. Poggio contributed the first chapter on magnetic resonanance force microscopy.

Prof. Poggio in Leoben

On the 13th, Prof. Poggio visited the lab of Prof. Aleksandar Matkovic at the Montanuniversität in Leoben, Austria. Along with touring the labs and discussing with Prof. Matkovic and his colleagues about an ongoing collaboraiton, Prof. Poggio gave a seminar entitled, “Scanning SQUID-on-tip microscopy of 2D and chiral magnetism “.

Prof. Aleksandar Matkovic Visits

Prof. Aleksandar Matkovic from the Montanuniversität in Leoben, Austria visited from on Monday the 29th. He gave a talk at the Quantum & Nano Seminar on Monday afternoon entitled, “Sheet silicate clays as functional gate insulators for two dimensional materials-based electronics”. He also visited our lab and spent time discussing an ongoing collaboration with members of the group.

Andriani and Daniel in Valencia

From the 21st to the 25th, Ph.D. students Andriani Vervelaki and Daniel Jetter attended the “European School on Superconductivity and Magnetism in Quantum Materials” in Valencia, Spain. The school provided a comprehensive series of foundational lectures, while also delving into the latest developments in the fields of superconductivity and magnetism. Cutting-edge advancements within these interdisciplinary fields were also discussed, as well as the synergies between superconductivity and magnetism.

Ph.D. Student Joins group

On the 10th, Antonella Restino joined the group as a Ph.D. student. Antonella received her Bachelor of Science in Physics in 2020 from University of Campania Luigi Vanvitelli in Italy. She went on to get her Masters degree in Physics in 2023 from the University of Naples Federico II under Profs. Tafuri and Massarotti. She has now moved to Basel for her Ph.D. Welcome!

Visit of Laura Heyderman

On the 22nd, Prof. Laura Heyderman from the PSI and ETH Zürich visited our department to give the Colloquium on the invitation of Prof. Poggio. Her talk was entitled, “Recent advances in artificial spin ice”. Prof. Heyderman spent the day in the Deparment and visited the group to discuss ongoing research.

High-school students visit lab

On the 21st, students in the final year of a high school from the Istituto d’Istruzione Superiore “James Clerk Maxwell” in Milano, Italy visited the department, on the invitation of Prof. Ilaria Zardo. As part of the visit, 2 groups of the 49 students were given a tour of our lab by post-doctoral researcher Dr. Francesco Fogliano, Ph.D. student Aris Lafranca, and Prof. Poggio. Further tours included the labs of Prof. Philipp Treutlein and Prof. Ilaria Zardo.

Paper on Magnetic Imaging of 2D Cr₂Ge₂Te₆ Published

On the 19th, Communications Materials published our article entitled, Visualizing thickness-dependent magnetic textures in few-layer Cr₂Ge₂Te₆. Therein we describe magnetic imaging experiments on few-layer Cr₂Ge₂Te₆ using a combined scanning superconducting quantum interference device and atomic force microscopy probe. Maps of the material’s stray magnetic field as a function of applied magnetic field reveal its magnetization per layer as well as the thickness-dependent magnetic texture. Using a micromagnetic model, we correlate measured stray-field patterns with the underlying magnetization configurations, including labyrinth domains and skyrmionic bubbles. By Comparing between real-space images and simulations, we demonstrate that the layer dependence of the material’s magnetic texture is a result of the thickness-dependent balance between crystalline and shape anisotropy. These findings represent an important step towards 2D spintronic devices with engineered spin configurations and controlled dependence on external magnetic fields.

The study was led and carried out by former post-doctoral researcher Dr. Kousik Bagani and Ph.D. students Andriani Vervelaki and Daniel Jetter. Research scientist Dr. Boris Groß provided input on the micromagnetic simulations. Samples were fabricated by members of the group of Prof. Peter Bøggild (DTU). Prof. Dennis Christensen (DTU) initiated the collaboration.

Roadmap on Magnetic Microscopy Published

On the 8th, Journal of Physics: Materials published a ‘roadmap’ article, in which experts in different areas of magnetic microscopy provide their views on the current capabilities of available techniques, forecast future advances, and assess how such advances may impact materials science. The work is entitled, 2024 Roadmap on Magnetic Microscopy Techniques and Their Applications in Materials Science. The focus of the article is on material science and physics. Prof. Dennis Christensen (DTU) led the team putting together the article, which included Dr. Urs Staub (PSI), Prof. Nini Pryds (DTU), Prof. Denys Makarov (HZD Dresden), and Prof. Poggio.

New Masters Students

Early this year, 3 new students have joined the group to pursue their Masters theses: Loris Durante, Katharina Kress, and Moritz Haberthür. Both Loris and Katharina have already worked in the group as part of one of their Masters projects. We welcome all three to the group and wish them luck on their projects!

Party for Kousik

On the 23rd, the group held a farewell party for Dr. Kousik Bagani, who will be leaving the group at the end of the month. Kousik joined the group in the midst of the COVID-19 pandemic in October 2020, after a post-doc in the lab of Prof. Eli Zeldov (Weizmann). Since then, he has led our efforts on developing SQUID-on-lever probes and applying them to the study of 2D magnets. He has also helped manage our FIBsuperProbes collaboration, taking over for Dr. Marcus Wyss. Kousik is now moving to Munich to start a job at Attocube AG. We wish him the best of luck in this new adventure and hope to continue working with him for a while longer on the projects he started. His contributions to the group — scientific and otherwise — will be missed by all!

NW MFM of bilayer EuGe₂

On the 15th, Nanoscale published our article entitled, Mapping the phase-separated state in a 2D magnet, as an “accepted manuscript” before the final edited and formated version appears. In the paper, we employ a high-sensitivity magnetic force microscopy (MFM) technique, using a nanowire (NW) transducer, to probe the spatial distribution of magnetic states in the paradigmatic 4f 2D ferromagnet EuGe₂. Below the ferromagnetic transition temperature, we discover the phase-separated state and follow its evolution with temperature and magnetic field. The characteristic length-scale of magnetic domains amounts to hundreds of nanometers. These observations strongly shape our understanding of the magnetic states in 2D materials at the monolayer limit and may contribute to engineering of future ultra-compact spintronic devices.

The research was carried out in our group by former Ph.D. student Dr. Hinrich Mattiat and current Ph.D. student Lukas Schneider, who did the MFM. The collaboration included Ph.D. student Patrick Reiser (Basel) and members of the Budakian group (University of Waterloo), who provided the NW MFM transducers. Members of the group of Prof. Vyacheslav Storchak (Kurchatov Institute) grew the EuGe₂ samples, carried out experiments using complementary techniques, and did analysis of the measurements. 

Scanning NV Magnetometry of Nanomagnets

On the 7th, ACS Applied Nano Materials published our article entitled, Scanning Nitrogen-Vacancy Magnetometry of Focused-Electron-Beam-Deposited Cobalt Nanomagnet. The work discusses the patterning of nanomagnets via focused-electron-beam-induced deposition (FEBID).  We report on the fabrication of cobalt nanomagnets and characterize their content, saturation magnetization, and stray magnetic field profiles, using a combination of transmission electron microscopy and scanning nitrogen-vacancy magnetometry. We find agreement between the measured stray field profiles and saturation magnetization with micromagnetic simulations. We further characterize magnetic domains and grainy stray magnetic fields in the nanomagnets and their halo side-deposits. The published work may aid in the evaluation of such nanomagnets for applications in spin qubits, magnetic field sensing, and magnetic logic.

The research was carried out by Ph.D. student Liza Žaper and the project was led by research scientist Dr. Floris Braakman. Research scientist Dr. Boris Groß helped with magnetic simulations. The work also benefitted from close collaborations with Dr. Peter Rickhaus (Qnami), Dr. Marcus Wyss (Nano Imaging Lab, Swiss Nanoscience Institute), and Dr. Kai Wagner (Maletinsky group, Department of Physics, University of Basel).

Swiss Quantum Days

From the 31st to February 1st, Prof. Poggio attended the first two days of the second edition of the Swiss Quantum Days in Villars-sur-Ollon, Switzerland. The conference focused on quantum materials, quantum sensing, quantum information, and quantum computation and included a number of prominent researchers in the field based in Switzerland.

Group Members at Nano in the Snow

From the 17th to the 19th, Ph.D. students Lukas Schneider, Luca Forrer, Mathias Claus, and Prof. Poggio attended this year’s edition of Nanoscience in the Snow, which was held at the Hotel Mont Paisible in Crans-Montana, Switzerland. Each presented a poster and Prof. Poggio gave a talk entitled, “Using nanomechanics to study nanomagnetism”.

Joe Wilcox Visits

From the 9th to the 11th, Dr. Joe Wilcox from the University of Bath, UK visited our group. Joe is an experimental physicist working on understanding the fundamental physics of unconventional superconductivity in the group of Prof. Simon Bending. Post-doctoral researcher Dr. Estefani Marchiori and Ph.D. student Lukas Schneider have started a collaboration with Joe.