iiinova — where your digital self keeps evolving

Joaquín Fernández-Rossier @jfrossier.bsky.social · 07/10/2025

Well, this goes to my bragging rights as predictor ☺️

Joaquín Fernández-Rossier @jfrossier.bsky.social · 07/10/2025

2) Deutsch, Shor, for their seminal contributions to quantum algorithms Now, my wish list: 1) Pablo Jarillo-Herrero and Allan Macdonald, for their seminal contributions to twistronics 2) Steve White, for inventing DMRG 3) Berry, for obvious reasons.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 07/10/2025

A few minutes before the announcement, let me go with my wish list/prediction for the Nobel Prize in Physics. First, the prediction 1) Martinis, Devore, Clarke, for the discovery of quantum behaviour of the relative phase in Josephson junctions. This makes superconducting quantum hardware possible.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 17/05/2025

The CrI3 tubes are encapsulated in multiwall carbon nanotubes. So, it is a 1D Van der Waals heterostructure. DFT calculations predict spin-proximity effect in this system, so, transport may be used to probe single-tube magnetism.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 17/05/2025

This is a first-timer: a hollow tube made of a monolayer magnetic material, CrI3. This may open a new field of research. On the theory side, given the strong-plane off-plane anisotropy of CrI3, tubes are expected to feature a radial magnetic state. www.nature.com/articles/s42...

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 17/05/2025

Check out our paper "One-dimensional CrI3 encapsulated within multi-walled carbon nanotubes", in collaboration with the group of L. Francis at INL and Manuel Valvidares at ALBA. We are reporting the first observation and characterization of a new type of nanostructure, a CrI3 nanotube.

nature.com

One-dimensional CrI3 encapsulated within multi-walled carbon nanotubes - Communications Chemistry

Producing single-walled inorganic nanotubes is challenging because their multi-walled counterparts are favored during synthesis. Here, the authors produce one-dimensional single-walled CrI3 encapsulat...

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Reposted by Joaquín Fernández-Rossier

Sabine Hossenfelder @hossenfelder.bsky.social · 15/04/2025

It was supposed to be impossible, but a group of researchers say they can generate electricity from Earth's magnetic field. I've had a look. www.youtube.com/watch?v=Qod2...

youtube.com

"Impossible" Device Creates Free Electricity from Earth's Magnetic Field

YouTube video by Sabine Hossenfelder

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 15/04/2025

The conference Condensed Matter in the City, held every other year in London, is accepting abstracts now. Focus topic: quantum materials. Very good list of invited speakers. I participated in 2023 and I loved it. research.kent.ac.uk/pqm/cmpcity2...

research.kent.ac.uk

Condensed Matter Physics in the City 2025 - RESEARCH GROUP / PHYSICS OF QUANTUM AND MATERIALS - Research at Kent

The Hubbard Theory Consortium's annual conference on Condensed Matter Physics, stimulating discussions linking Experiment and Theory.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 25/03/2025

How did it take 14 years for me to find out this great talk by Don Eigler about one of my favorite topics? www.youtube.com/watch?v=rd2d...

youtube.com

TEDxCaltech - Don Eigler - Moving Atoms, one-by-one

YouTube video by TEDx Talks

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

This work is yet another proof that nanographenes are ideal building blocks to create artificial spin lattices, explore quantum magnetism, and start thinking about ways to exploit it. I thank all my coworkers, funding agencies and the INL for making this research possible.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

Building on that preprint, we relate the modulation of the zero bias Kondo peak observed in the nanographene chains with odd number of spins to the wave function of a single spinon standing wave. So, in this sense, we are taking a picture of an individual spinon.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

Very much like protons are bound states of 3 quarks, the spin excitations of the spin chains are made of spinon pairs. Single spinons behave like free fermions, but is hard to observe them. In our work, we provide a proxy way to do so, inspired in this theory preprint: arxiv.org/abs/2303.02276

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

Using inelastic electron tunnel spectroscopy with scanning tunnel microscopes (IETS-STM), they measure the energy of the spin excitations as a function of the chain length. We have modelled their results. The spin excitations in this system are quite peculiar: they are bound states of spinons.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

The Heisenberg model used to be a "textbook case" of mathematical physics and theoretical quantum magnetism. With our paper, it now becomes a textbook case of surface physics and organic chemistry. Our colleagues are able to fabricate many spin chains with different length.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

At my group, the heavy lifting was done by , including PhD students, Joao Carlos Henriques and Mar Ferri. We have studied antiferromagnetically coupled S=1/2 spin chains made with olympicenes, Olympic ring shaped nanographenes. They realize the so called Heisenberg spin model.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 14/03/2025

Today our paper "Spin excitations in nanographene-based antiferromagnetic spin-1/2 Heisenberg chains" has been published in Nature Materials. www.nature.com/articles/s41... This is a collaboration with the groups of @rfasel.bsky.social at EMPA, Xingliang Feng at MPI and TUD, and my group at INL.

nature.com

Spin excitations in nanographene-based antiferromagnetic spin-1/2 Heisenberg chains - Nature Materials

Open-shell nanographenes are used to fabricate length-controlled antiferromagnetic spin-1/2 Heisenberg chains. It is revealed that the spin excitation spectra evolve from gapped to gapless following a...

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

In contrast, spin excitations in the S=1/2 Heisenberg chains with OBC are not standing waves. Crucially, we find that whether or not the excitations of the open-end chains are wave packets of the PBC chains determines the capability to infer E(k) of spin excitations out of the FT of IETS.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

Some elementary excitations, such as magnons in ferromagnetic chains and triplons in the alternate exchange Heisenberg chain, whose wave function in spin chains with open boundary conditions (OBC) are standing waves: linear combinations of pairs of states of the chains with periodic BC (PBC). 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

Now, we can take the FT of that image and try to relate to the E(k) of the spin chains. There are several reasons why this may fail, but the fact is that, in some cases, it happens to work. That's what our preprint is all about. arxiv.org/abs/2502.13770. Our key findings are the following: 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

The principle of inelastic electron spectroscopy (IETS) is that inelastic excitations appear as steps in the dI/dV curve for eV= E, where E is the energy of a given excitation. In spin chains, the magnitude of the step is different as the dI/dV is measured in different spins. This provide an image.

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

Thus, FT at a given bias will have information of the electrons with energy Ef+eV. This allows to pull out a map of E(k) (some restrictions apply). Now, with this hindsight, we can try to play the analogous game with inelastic spin excitations in spin chains . 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

The trick is the following: in the presence of elastic scattering, electrons with momentum k will form standing waves with momentum 2k. Now, at a given bias V, STM is scanning states with energy Ef+ eV, where Ef is the Fermi energy. 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

So, STM does not gather momentum information, or not in a direct manner. Now, the STM takes images in the (x,y) plane of the surface at a given voltage V. The Fourier transform (FT) of those images has been used, for instance, to infer the energy dispersion of electrons on the surface. 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

STM is a very different type of experiment. Electrons tunnel from an atomically sharp tip. Therefore, on account of Heisenberg principle, their in-plane momentum is not well defined. Their off-plane momentum either, as they are evanescent waves. In addition, their momentum is not measured. 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

So, standard techniques to probe E(k) such as ARPES (angle resolved photoemission spectra), neutron scattering and Brillouin scattering excite the sample with photons or neutrons with well defined energy and momentum, and probe the energy and momentum of outgoing particles. 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 23/02/2025

Can you use (Scanning Tunnel Microscopy) STM to determine the energy dispersion of spin excitations in spin chains? Well, in our latest preprint (arxiv.org/abs/2502.13770) we give the answer: it depends. Some context: excitations in crystals have energy E and momentum, k. 👇

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 12/02/2025

It would be amazing if the same technology that makes LLM work helps us tackle the many body problem

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 12/02/2025

I wish days had 48 hours to be able to catch up with so many exciting things going on in Science these days. This paper got my eye (I was going to say attention, but that would be misleading, check the title): arxiv.org/abs/2502.05383.

arxiv.org

Is attention all you need to solve the correlated electron problem?

The attention mechanism has transformed artificial intelligence research by its ability to learn relations between objects. In this work, we explore how a many-body wavefunction ansatz constructed fro...

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Joaquín Fernández-Rossier @jfrossier.bsky.social · 11/02/2025

Hi bsky, I have just created my account here, to discuss about science (mostly condensed matter theory, quantum sensing, quantum computing) with colleagues and friends.

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