News

QSIT Zoom Seminar

On Thursday the 14th, Prof. Poggio gave an online seminar for a new series of teleconference seminars organized by the NCCR QSIT. The seminar was entitled, “Imaging weak magnetic field patterns on the nanometer-scale” and can be found here.

Lorenzo Ceccarelli Earns Ph.D.

On Friday the 8th, Ph.D. student Lorenzo Ceccarelli defended his thesis, entitled “Scanning probe microscopy with SQUID-on-tip sensor”, earning his doctorate in Physics magna cum laude. The exam was chaired by Prof. Christoph Bruder with Prof. Poggio and Prof. Jose María De Teresa (Zaragoza) making up the committee. Lorenzo joined the lab as a Ph.D. student in January 2016 to work on the development and application of scanning SQUID-on-tip sensors. He was the first student to work on this project full time and carried out our first two experiments using this technique. The first was show the presence of flux-closure configurations in individual ferromagnetic nanotubes. The second investigated superconducting vortex dynamics and pinning in an amorphous superconducting film of MoSi.

Due to the restrictions due to the Coronavirus pandemic, the defense was carried out largely by teleconference. Unfortunately, this prevented the group from properly celebrating Lorenzo’s accomplishments. Given that he is staying on as a post-doctoral researcher, hopefully we will soon get a chance to throw him an appropriate party. Congratulations to Dr. Ceccarelli!

Masters Student to Start as Ph.D.

Lukas Schneider completed his Masters thesis in our lab at the beginning of this month on, “Scanning probe microscopy with lasing nanowires”.  After a short break from the group to complete his civil service, Lukas will start on July 1st in the group as a Ph.D. student. His position is funded by by the Swiss Nanoscience Institute through their Ph.D. School on a project entitled, “Magnetic force microscopy with nanowire transducers”.

New FET Open Project Approved

Our group recently won an FET Open project grant under the European Commission’s Horizon 2020 program. This funding scheme supports European collaborations aimed at developing radically innovative technologies. We will be the lead partner in a project entitled, “Focused Ion Beam fabrication of superconducting scanning Probes (FIBsuperProbes)”. Working with researchers from IBM Research in Zürich, the University of Tübingen, and the Consejo Superior de Investigaciones Cientificas (CSIC) in Zaragoza, we plan to develop a new method — based on forcused ion beam (FIB) technology — of fabricating nanometer-scale superconducting scanning probes. Starting in October 2020, the FET Open will provide nearly 3M EUR of research funds to the 4 partner groups over the course of 3.5 years. See here for a write-up.

Masters Student Starts Work

This month, Mathias Claus started work as a Masters Student working on ultra-sensitive sensors for torque magnetometry. Mathias received his Bachelor of Science in Nanoscience in 2019 from the University of Basel. He joins the group after doing one of his Masters works on a related project.

Paper on MFM using nanowires fabricated by FEBID

On the 16th, Physical Review Applied published our paper entitled, Nanowire magnetic force sensors fabricated by focused-electron-beam-induced deposition. The manuscript demonstrates the use of individual magnetic nanowires (NWs), grown by focused-electron-beam-induced deposition (FEBID), as scanning magnetic force sensors. Our measurements of their mechanical susceptibility, thermal motion, and magnetic response show that these NWs possess high-quality flexural mechanical modes and a strong remanent magnetization pointing along their long axis. Together, these properties make the NWs excellent sensors of weak magnetic field patterns, as confirmed by calibration measurements on a micron-sized current-carrying wire and magnetic scanning-probe images of a permalloy disk. The flexibility of FEBID in terms of the composition, geometry, and growth location of the resulting NWs, makes it ideal for fabricating scanning probes specifically designed for imaging subtle patterns of magnetization or current density.

Ph.D. student Hinrich Mattiat led the research and carried out the experiments in collaboration with Dr. Nicola Rossi. Dr. Boris Groß developed and ran the micromagnetic simulations. Collaborators from the University of Zaragoza fabricated the magnetic NWs by FEBID, while collaborators from Case Western University fabricated the permalloy micro-disks used as demonstration samples.

Book Chapter on Magnetic Nanotubes

On the 1st, Elsivier published the second edition of a book entitled, Magnetic Nano- and Microwires: Design, Synthesis, Properties and Applications, edited by Prof. Manuel Vázquez. Chapter 17, which is written by Prof. Poggio, is entitled, Determining magnetization configurations and reversal of individual magnetic nanotubes. It focuses on ferromagnetic nanotubes (FNTs) and their experimental investigation by techniques capable of measuring the response of individual specimens. This capability has been developed recently and is now having a strong impact on our understanding of the behavior of real FNT structures. The chapter reviews measurements of magnetoresistence, torque magnetometry, X-ray microscopy, scanning SQUID microscopy, and magnetic force microscopy.

Reduced Operations due to Public Health Emergency

Because of the world-wide public health emergency, the University of Basel, the Department of Physics, and our group have been gradually scaling back operations over the last month. All seminars, conferences, and travel have been cancelled. Since the 22nd, the department and our lab are operating under emergency rules. Only critical experiments continue in our labs under strict social distancing rules, while group members work from home as much as possible.

Estefani Wins Post-doc Award

On Friday the 7th, post-doctoral researcher Dr. Estefani Marchiori won a QSIT INSPIRE Postdoc Award. This competitive award recognizes outstanding female scientists at the post-doc level within the QSIT network. The award includes a 10k CHF grant for travel and small equipment expenditures. Congratulations Estefani!

Thibaud Skis to Second Consecutive QSIT Victory

On Thursday the 6th, Ph.D. student Thibaud Ruelle won the annual QSIT ski race in at the NCCR QSIT General Meeting in Arosa, Switzerland for the second year in a row. Just like last year, Thibaud predicted victory and mercilessly crushed the competition. Congratulations again!

Group at Arosa Winter School and General Meeting

From the 3rd to the 7th, members of the group attended the 9th NCCR Winter School and 10th NCCR QSIT General Meeting in Arosa, Switzerland. Masters students Lukas Schneider and Arsalan Saeedi attended the school from Monday to Wednesday, while Ph.D. students Hinrich Mattiat, Lorenzo Ceccarelli, Giulio Romagnoli, Thibaud Ruelle, post-doc Dr. Estefani Marchiori, and Prof. Poggio attended the meeting from Wednesday to Friday. Dr. Floris Braakman also attended the meeting in his role as senior scientist in the Zumbühl group. Hinrich, Lukas, and Thibaud presented posters on their work. Thanks to Klara Berg of QSIT for organizing another successful meeting.

Nanoskyrmionics Ski Retreat

From the 28th to the 30th, our Nanoskyrmionics Sinergia Network held a ski retreat a “Zschokke Haus” chalet of the University of Basel, located on Gerschni Alp at the foot of Mt. Titlis in Engelberg, Switzerland. The event was an opportunity for skiing, scientific discussions, and socializing between network members. Post-doc Dr. Boris Groß and Ph.D. student Simon Philipp from our group were in attendance. Special thanks to Simon for helping to organize the event.

News & Views in Nature Physics

On Wednesday the 8th, Nat. Phys. published a commentary piece by Prof. Poggio and post-doctoral researcher Dr. Nicola Rossi entitled, Currents cool and drive, discussing two recent papers describing electromechanical experiments in suspended carbon nanotubes. In particular, the piece highlights recent work showing that electrons driven through a suspended carbon nanotube by a constant bias excite mechanical vibrations — including self-sustaining oscillations — and, in some cases, even suppress them down to only a few quanta. The experiments in question are described in papers by Adrian Bachtold and colleagues and by Edward Laird and colleagues.

New Masters Student Starts

On Tuesday the 7th, Daniel Jetter started work in our lab as a visiting Masters student. Daniel received his Bachelor of Science from the University of Tübingen in 2019. He will pursue his Masters project on scanning nanometer-scale SQUID microscopy in our lab, while continuing to be enrolled as a student of the University of Tübingen. Prof. Reinhold Kleiner in Tübingen will serve as his Masters advisor and Prof. Poggio will host the project.

Artificial Spin Ice Paper Published

On Tuesday the 10th, the journal ACS Nano published our paper entitled, Stray-Field Imaging of a Chiral Artificial Spin Ice during Magnetization Reversal, as a “Just Accepted Manuscript”. The manuscript describes our use of a scanning nanometer-scale superconducting quantum interference device (SQUID) to image the magnetic stray field distribution of an artificial spin ice system exhibiting structural chirality as a function of applied magnetic fields at 4.2 K. The images reveal that the magnetostatic interaction gives rise to a measurable bending of the magnetization at the edges of the nanomagnets. Micromagnetic simulations predict that, owing to the structural chirality of the system, this edge bending is asymmetric in the presence of an external field and gives rise to a preferred direction for the reversal of the magnetization, an effect not captured by models assuming a uniform magnetization. Our technique thus provides a promising new means for understanding the collective response of artificial spin ices and their interactions.

Post-doc Dr. Marcus Wyss led and carried out the experiments in our lab with help from Dr. Denis Vasyukov, Lorenzo Ceccarelli, and Giulio Romagnoli. Dr. Sebastian Gliga, the corresponding author, and his collaborators fabricated the artificial spin ice and carried out the simulations.

Prof. Manuel Vázquez Visits

On Monday the 21st, Prof. Manuel Vázquez from the Instituto de Ciencia de Materiales, CSIC, in Madrid was invited by Prof. Poggio to give the Nano and Quantum Seminar here in the department. His talk was entitled, “Modulated cylindrical nanowires: from synthesis to domain structure and magnetization reversal”. Prof. Vázquez, who is an expert in magnetic nanowires, visited our group on Monday and Tuesday to discuss potential collaborations.

Marcus Wyss Speaks in Tübingen

On Friday the 11th, Dr. Marcus Wyss gave the Institutsseminar at the Center for Quantum Science in the Physics Department of the University of Tübingen.  His talk was entitled, “Nanoscale Imaging of magnetic structures”. Prof. Poggio and Dr. Boris Groß joined Marcus for the visit and the two spent Thurday and Friday discussing collaborative projects with their host, Prof. Dieter Kölle and his group members.

Group Bike Tour

On Sunday the 6th, group members went on a bike tour from the department to Rötteln Castle, just outside Basel in Lörrach, Germany. Although a persistent rain deterred us from making it up to the castle, the weather and two flat tires couldn’t stop us from enjoying some roadside whiskey and a hearty lunch at the Brauhaus Lasser. Thanks to Giulio Romagnoli for organizing. Pictures are here.

Masters Student Joins Group

Arsalan Saeedi joined our group as a Masters student in early October. Arsalan received his Bachelor of Science in Physics from the University of Basel in 2017. He is joining our lab to do his Masters project on integrating a nanomechanical oscillator into a high-finesse optical cavity.

Introduction to Nanomechanics Starts

On Wednesday the 18th, the Master-level lecture “Introduction to Nanomechanics” started. The lecture will take place every Wednesday from 10:00 to 12:00 in 1.22 until the 18th of December. The course (not surprisingly) focuses on the mechanics of very small objects. In particular, we will discuss the regime of nanometer-scale objects where classical theory begins to break down and quantum mechanical behavior emerges. In order to do so, we will touch on continuum mechanics, statistical mechanics, opto-mechanics, and quantum mechanics. After covering the fundamentals of the field, we will study its most important results up to and including contemporary work. We will discuss efforts to bring nanomechanical resonators into the quantum mechanical regime. We will also emphasize the most practical and successful applications of these devices, i.e. as sensors of force, mass, and displacement.

Masters Student Joins Group

Lukas Schneider joined our group as a Masters student in mid-September. Lukas received his Bachelor of Science in Nanoscience from the University of Basel in 2018. He carried out one of his two short Masters projects in our lab on magnetic nanowire (NW) sensors. He will continue work in this direction during his full Masters project, working on NW as scanning probe sensors.

Paper on Imaging Superconducting Vortices Published

On Thursday the 5th, Physical Review B, published our article entitled, Imaging pinning and expulsion of individual superconducting vortices in amorphous MoSi thin films. The manuscript reports the first images of individual superconducting vortices in thin films used in the production of sensitive photon detectors. Superconducting vortices are tiny whirl-like configurations of supercurrent, which flow around a non-superconducting core and allow a quantum of magnetic flux to penetrate a superconductor. Newly developed superconducting nanowire single photon detectors (SNSPDs) are fast, efficient, and extremely sensitive, making them attractive for many cutting-edge applications. How exactly they work, however, remains poorly understood. Recently, evidence has emerged that superconducting vortices are crucial both in the mechanism used for the detection of photons and in the generation of dark counts. For this reason, we used an ultra-sensitive nanometer-scale superconducting quantum interference device (SQUID) fabricated on the end of a sharp scanning probe – a so-called SQUID-on-tip – to investigate vortices in MoSi, one of the materials used in SNSPDs. The tiny scanning probe made images showing where the vortices appear, how they move, and how they get trapped – or ‘pinned’ – on defects in the material. The work suggests that control of the density and strength of these pinning sites is important for the optimization of SNSPD devices based on amorphous thin films. Given that vortex motion contributes to loss in many superconducting circuits – including those used as qubits in quantum computers – such experiments may prove useful on a variety of other superconducting circuits.

Ph.D. student Lorenzo Ceccarelli carried out the experiments, analyzed the data, and led the work. Early contributions were made by former post-doc Dr. Denis Vasyukov. Post-docs Dr. Marcus Wyss, Dr. Nicola Rossi, and Ph.D student Giulio Romagnoli made various contributions to the experiments with Nicola also contributing to the figures for the manscript. Post-doc Dr. Lucas Moser of the Meyer group carried out X-ray photoelectron spectroscopy of the MoSi samples.

New Department Chair

Effective on the 1st, Prof. Poggio took over from Prof. Dominik Zumbühl as the new Chair of the Department of Physics.