Inaugural lecture Prof. dr. A. F. Otte


On Wednesday September 11th, Sander Otte gave his inaugural lecture as Antoni van Leeuwenhoek Professor. During his 30-minutes public lecture, he took his audience to the border between classical physics and quantum physics. Highlight of the lecture was a live demonstration of an experiment on structures of actual magnetic atoms, positioned in such a way as to visualize the existence of this border.

You can watch the lecture, which was in Dutch, here.

NWO Vici grant for Sander Otte


Sander Otte has been awarded a Vici career grant by Netherlands science organisation NWO. In the coming five years, we will use this funding to setup a research direction where we use STM-based electron spin resonance to study the dynamic behaviour of collective excitations in atomic spin chains. More information can be found here.

Publication in Surface Science


In our newest publication in Surface Science, we present controlled growth of c(2  ×  2)N islands on the (100) surface of Cu3Au, which can be used as an insulating surface template for manipulation of magnetic adatoms. Compared to the commonly used Cu(100)/c(2  ×  2)N surface, where island sizes do not exceed several nanometers due to strain limitation, the current system provides better lattice matching between metal and adsorption layer, allowing larger unstrained islands to be formed. We show that we can achieve island sizes ranging from tens to hundreds of nanometers, increasing the potential building area by a factor 100. Initial manipulation attempts show no observable difference in adatom behaviour, either in manipulation or spectroscopy.

STM topography of a single nitride island on Cu3Au with a diameter of 40 nm. On the island, two manipulated structures composed of Fe atoms are visible.


Atomic arrays paper in SciPost Physics


Have a look at our latest paper, published in SciPost Physics. Here we report on the investigation of atomic arrays of various shapes and sizes, built out of individual atomic vacancies. This way, we construct small artificial two-dimensional materials which show the beginnings of band formation.

SciPost is a recently initiated publication portal that is fully open-access. In contrast to most other journals, it features ‘peer-witnessed’ review. This means that the refereeing process is completely open and that anyone – so not just the invited referees – can contribute comments, resulting in a fair and transparent review process.

STM topography and corresponding local electron tunneling spectroscopy on various arrays built from atomic vacancies in the CuCl/Cu(100) surface. It can be observed that for denser lattices, the onset of the conduction band – originally at 3.5 eV – is shifted further downward.

Lecture at ‘Diligentia’


On April 3rd, Sander Otte gave a lecture at the Koninklijke Maatschappij voor Natuurkunde ‘Diligentia’ in the Diligentia Theatre in The Hague. This one hour lecture, in Dutch, provides an overview of the field and discusses several concepts on a level that is accessible to first-year college physics students.

A kilobyte rewritable atomic memory


Every day, modern society creates more than a billion gigabytes of new data. To store all this data, it is increasingly important that each single bit occupies as little space as possible. As reported in Nature Nanotechnology today, Floris Kalff and coworkers managed to bring this reduction to the ultimate limit: they built a memory of 1 kilobyte (8,000 bits), where each bit is represented by the position of one single chlorine atom.

With an areal storage density exceeding 500 Terabits per square inch, the memory outperforms existing state-of-the-art harddisk drives by three orders of magnitude. In theory, with this storage density all books ever written by mankind could be spelled out on the surface of a postage stamp.

Apart from being the largest atomically assembled architecture ever created, the memory also features the first demonstration of atomic-scale markers that allow the STM tip to navigate through the large array of bits. Markers indicate the start and end of each line, but can also state if a sector cannot be used for data storage due to contamination or a crystal defect. Such protocols are crucial for scaling-up technology beyond a few hundred bits.

The movie below demonstrates the mechanism of the atomic storage memory.


Check here for an overview of press coverage of ‘the kilobyte’.

Quantum criticality paper in Nature Physics


Phase transitions, such as the transition between a solid and a liquid, play an important role in condensed matter physics. Since the number of participating particles is huge, it is practically impossible to predict the exact behaviour of a material near a phase transition: this is what makes them so intriguing.

An extra fascinating class of phase transitions consists of those transitions in which not thermal fluctuations, but quantum fluctuations drive the change in the material. These quantum phase transitions are maintained even at zero temperature. In general it is very difficult to probe a quantum phase transition experimentally, as in practice it is often overshadowed by more mundane effects.

Ranko Toskovic and coworkers now report in Nature Physics that they have succeeded in designing and building tiny ‘materials’ consisting of only a few atoms, exactly in such a way that they display the beginnings of quantum criticality. The materials consist of magnetic atoms that prefer to align in an alternating fashion. Only when a magnetic field of 6 Tesla is applied, they collectively surrender and point in the same direction. This transition is not sudden, but consists of a number of discrete quantum jumps, which the researchers could observe in detail. Together, these jumps constitute the start of a quantum phase transition.

Scanning tunnelling spectroscopy measurements taken on each atom of chains with lengths ranging from one (left) to six atoms (right). At predicted magnetic field strengths (red dashed lines) the spectroscopic features show sudden jumps. These jumps get closer as the critical field value of 6 Tesla is reached, after which the transition to the paramagnetic phase is complete.

ERC Starting Grant for Sander Otte


Sander Otte has been awarded an ERC Starting Grant for his research proposal Spin correlations by atomic design (SPINCAD). In this project, Otte will investigate collective dynamics in artificially designed atomic spin structures. The excitations of such spin lattices, such as spinons or magnons, can be viewed as quantum-mechanical quasiparticles that propagate at tremendous speeds. The implementation of atomically crafted detectors may help to visualise the motion of these elementary particles with atomic local precision.

The ERC Grant represents a sum of 1.45 million euro’s, to be spent in the coming five years. A large part of this budget will be used to employ PhD students and postdoctoral researchers. Employment opportunities will be announced soon on our openings page.