News

Lorenzo at Coma-ruga

From the 1st to the 5th, Ph.D. student Lorenzo Ceccarelli attended the 15th International Workshop on Magnetism & Superconductivity at the Nanoscale (Coma-ruga 2019) in Coma-ruga, Spain. This annual event includes discussion and presentations in all areas of nanomagnetic and superconducting research, including spintronics, novel magnetic and superconducting phases, and low-dimensional systems. Lorenzo gave a talk about his most recent work on the evening of the 1st entitled, “Imaging superconducting vortex dynamics in amorphous MoSi thin films”.

Drawing of Nicola by Ph.D. student Lorenzo Ceccarelli

Nicola Rossi Graduates

On the 1st, Ph.D. student Nicola Rossi defended his thesis, entitled “Force sensing with nanowires”, earning his doctorate in Physics summa cum laude. The exam was chaired by Prof. Ernst Meyer with Prof. Poggio and Prof. Adrian Bachtold (ICFO, Barcelona) making up the committee. Nicola started as a Ph.D. student in June 2014 with the support of our ERC Starting Grant on using nanowires (NWs) as sensitive scanning probes. Nicola was the first to demonstrate a new type of atomic force microscope (AFM) using NWs as sensitive transducers. Unlike standard AFM, the NW-based technique enables measurements of both the size and direction of forces. He later showed that magnet-tipped NWs can be used for imaging extremely weak magnetic field patterns on the nanometer-scale, as required for mapping mesoscopic transport and spin textures or in nanometer-scale magnetic resonance. Fortunately for us, Nicola will stay at least until the end of the year to finish some ongoing scientific projects here in the lab. Congratulations to Dr. Rossi!

New Post-doc Starts

On the 1st, Dr. Estefani Marchiori started work in the group as post-doctoral researcher. Estefani earn her Ph.D. in Physics in the spring of 2019 from the University of Bath. There she worked with Prof. Simon Bending, studying the interplay between ferromagnetism and superconductivity at the nanometer-scale through measurements of transport, magnetization, and by scanning Hall microscopy. The aim was to understand and control odd frequency spin-triplet superconducting correlations (long range proximity effects) in hybrid structures. Welcome Estefani!

Annual Birsköpfli BBQ

On the 30th, group members, alumni and alumnae, and friends met up for for the 3rd year at the Birsköpfli park along the Rhine river for a barbecue, drinks, games, and cooling off in the river. Thanks to all for a good time! Pictures and movies are here.

Floris in Firenze

From the 4th to the 5th, Dr. Floris Braakman attended a mid-term meeting of the Quantera project “QuaSeRT” in Firenze, Italy. The meeting was held at the last home of Galileo Galilei, Villa “Il Gioiello”. As a researcher outside the QuSeRT collaboration, Floris gave a talk on the 5th describing our recent work in nanowire sensing and optomechanics.

Sola Basel

Processed with MOLDIV

On the 25th, Ph.D. students Hinrich Mattiat and Giulio Romagnoli and Prof. Poggio took part in the 2^nd annual Sola Basel running relay along with members of the Zardo Group and friends. The 10-person teamed ended up in 29^th place with help from Giulio, Hinrich, and Martino placing 10^th, 14^th, and 17^th in their respective legs.

Paper Published in Applied Optics

On the 6th, Applied Optics published our manuscript entitled, Optimized single-shot laser ablation of concave mirror templates on optical fibers. The manuscript describes a process for realizing mirror templates on the tips of optical fibers by single-shot CO₂ laser ablation. It also presents a systematic study of the influence of the pulse power, pulse duration, and laser spot size on their geometry. The investigation provides new insights into CO₂ laser ablation of optical fibers and should help improve current models. Notably, the study finds that the radius of curvature, depth, and diameter of the templates exhibit extrema as a function of the power and duration of the ablation pulse, and shows that compound convex–concave shapes can be obtained. In the paper, we also identify regimes of ablation parameters that lead to mirror templates with favorable geometries for use in cavity quantum electrodynamics and optomechanics.

Ph.D. student Thibaud Ruelle was the driving force behind this work, carrying out the experiments and modelling the results. Dr. Floris Braakman led and supervised the work as part of his 2015 Ambizione grant from the Swiss National Science Foundation.

Basel-Zürich 3-1

On the 25th, post-doc Dr. Marcus Wyss and Ph.D. student Giulio Romagnoli traveled to the Letzigrund stadium to represent the group in support of the local football club at the semi-final of the 2019 Swiss Cup. They enjoyed watching FC Basel thrash a team from a neighboring city in a 3-1 victory worth a spot in the Swiss Cup final. A good time was had both at the match and on the ride to and from the game on a ‘special’ train for FC Basel fans.

Zurich Instruments User Meeting

On the 25th and 26th, Ph.D students Thibaud Ruelle, Hinrich Mattiat, Simon Philipp, and Nicola Rossi; post-doc Dr. Boris Groß; and Prof. Poggio attended the 3rd Zurich Instruments User Meeting on SPM & Magnetism held at ETH Zürich. The meeting was hosted by Prof. Christian Degen and included talks, practical tutorials, and tours of labs and of Zurich Instruments headquarters. Prof. Poggio gave a talk on the morning of the 25th entitled, “New scanning probes for nanomagnetic imaging”.

Review on Nanowire Force Sensing Published

On the 16th, Nanotechnology published a topical review written by Dr. Floris Braakman and Prof. Poggio entitled, Force sensing with nanowire cantilevers. The paper discusses the motivation behind using nanowires as force transducers, explain the methods of force sensing with nanowire cantilevers, and gives an overview of the experimental progress so far and future prospects of the field.

Prof. Poggio at DPG Spring Meeting

On the 2nd, Prof. Poggio gave an invited talk at the annual Spring Meeting of the Deutsche Physikalische Gessellschaft (DPG) in Regensburg, Germany. On the invitation of session organizer, Dr. Denys Makarov, Prof. Poggio gave a talk entitled, “Magnetization configurations and reversal of individual ferromagnetic nanotubes“. This talk was part of a special symposium on “Geometry, Topology, and Condensed Matter“.

Seminar at Walter Schottky Institute

On the 1st, Prof. Poggio visited Prof. Gregor Kolbmueller and Prof. Jonathan Finley at the Walter Schottky Institute (WSI) of the Technical Univeristy of Munich (TUM). He discussed an ongoing collaboration and visited research groups at TUM. In the afternoon, he gave a ‘Schottky Seminar’ entitled, “New scanning probes for nanomagnetic imaging“.

Group at APS March Meeting

From the 4th to the 8th, members of the group attended the annual APS March Meeting, which was held in Boston this year. Ph.D. students Hinrich Mattiat, Nicola Rossi, and Lorenzo Ceccarelli; post-docs Dr. Floris Braakman and Dr. Marcus Wyss; and Prof. Poggio made the trip to attend the 11,000-person conference. Hinrich gave a talk entitled, “FEBID-grown iron and cobalt nanowires as magnetic force sensors“; Nicola a talk entitled, “Magnetic force sensing using a self-assembled GaAs nanowire with a MnAs tip“; Lorenzo a talk entitled, “Imaging individual superconducting vortices in amorphous Mo_0.8Si_0.2 by scanning SQUID-on-tip“; Marcus a talk entitled, “Imaging the stray field of chiral artificial spin ice with scanning nanoSQUID-on-tip“; and Floris a talk and a poster entitled, “Optimized single-shot laser ablation of concave mirror templates on optical fibers” and “Hole spins in Ge/Si nanowires“, respectively.

Physics II for Physicists Starts

On Thursday the 21st, the lecture “Introduction to Physics II for Physicists: Electrodynamics and Optics” began and will run until Friday, May 24th. The exam is scheduled for June 20st, 2019, 10:00 – 13:00. The lecture covers the basics of electrostatics, magnetostatics, electrodynamics, and optics. Prof. Philipp Treutlein and Prof. Poggio are sharing lecturing responsibilities.

Group Members at Arosa Meeting or Lorenzo Speaks and Thibaud Knows He’s #1

From the 4^th to the 8^th, members of the group attended the 8^th NCCR Winter School and 9^th NCCR QSIT General Meeting in Arosa, Switzerland. Ph.D. student Hinrich Mattiat attended both the school and the meeting, while Ph.D. students Lorenzo Ceccarelli, Giulio Romagnoli, Thibaud Ruelle, post-doc Boris Groß, and Prof. Poggio attended the meeting. Hinrich and Thibaud presented posters on their work and Lorenzo gave a talk on the 8^th entitled, “Imaging individual superconducting vortices in amorphous Mo Si by scanning SQUID-on-tip”. On the afternoon of the 7^th, Thibaud — after predicting victory — crushed the competition and won the annual QSIT ski race, becoming the first group member to do so. Congratulations! Also, a special thanks to Ilona Blatter for her long and crucial service to QSIT and to Klara Berg for organizing and excellent meeting.

Floris at Nano in the Snow

From the 23rd to the 25th, post-doc Dr. Floris Braakman attended the annual “Nanoscience in the Snow” Workshop organized by the Swiss Nanoscience Institute and held this year at the Hotel Crystal Braunwald. Floris gave a talk in the morning of Thursday the 24th.

Nanowire MFM Paper Published

On the 2nd, our manuscript entitled, Magnetic force sensing using a self-assembled nanowire, was published by Nano Letters. In the study, we present a scanning magnetic force sensor based on an individual magnet-tipped GaAs nanowire (NW) grown by molecular beam epitaxy. Its magnetic tip consists of a final segment of single-crystal MnAs formed by sequential crystallization of the liquid Ga catalyst droplet. We characterize the mechanical and magnetic properties of such NWs by measuring their flexural mechanical response in an applied magnetic field. Comparison with numerical simulations allows the identification of their equilibrium magnetization configurations, which in some cases include magnetic vortices. To determine a NW’s performance as a magnetic scanning probe, we measure its response to the field profile of a lithographically patterned current-carrying wire. The NWs’ tiny tips and their high force sensitivity make them promising for imaging weak magnetic field patterns on the nanometer-scale, as required for mapping mesoscopic transport and spin textures or in nanometer-scale magnetic resonance.

Ph.D. student Nicola Rossi led the research and carried out the experiments. Dr. Boris Groß developed and ran the micromagnetic simulations. Ph.D. student Florian Dirnberger and Prof. Dominique Bougeard from the Universität Regensburg grew the magnet-tipped NWs used in the experiments.