Jochim Labs

Our recent work on Fermion pairing in two dimensions has been selected for publication in Science magazine.

The press release from Heidelberg University:
https://www.uni-heidelberg.de/presse/news2017/pm20171221_exploring-the-phenomenon-of-superconductivity.html

High-temperature pairing in a strongly interacting two-dimensional Fermi gas The nature of the normal phase of strongly correlated fermionic systems is an outstanding question in quantum many-body physics. We use spatially resolved radio-frequency spectroscopy to measure pairing energy of fermions across a wide range of temperatures and interaction strengths in a two-dimensi...

Please check out the upcoming conference “Beyond Digital Computing: The Power of Quantum and Neural Networks”, which will be held at the International Academic Forum (IWH) Heidelberg from 19 to 21 March 2018.



This collaboration between the Physics and the Kirchhoff Institute will bring together experts on quantum simulation, neuromorphic computing and machine learning.

bdc.physi.uni-heidelberg.de

Recently two of our PhD students graduated. Congratulations Mathias Neidig and Andrea Bergschneider for the very successful PhDs and good luck for the future!

Selim Jochim erhält ERC Consolidator Grant Europäischer Forschungsrat fördert Forschungsprojekt mit rund zwei Millionen Euro

Congratulations to Michael Kosterlitz, David Thouless and Duncan Haldane for winning the 2016 Nobel Prize in Physics!

In 1970s Kosterlitz and Thouless made the seminal discovery that when matter is flattened out to two dimensions,
it can undergo fundamentally different kinds of phase transition - known as topolical transitions that are governed purely by the system's topology and not so much by its microscopic properties (see the explanation with bagels in the announcement video).
Their work has led to deep insights into phase transitions in general and particularly in the context of superfluidity, superconductivity. Duncan Haldane has made fundamental discoveries, most notably on how topology influences the phenomena of magnetism in 1D chains.

We are extremely excited by this year's prize also because the work of all three winners have been influential for our recent experiments! In one of our experiments, we were able to experimentally observe the Berezinskii-Kosterlitz-Thouless transition in a gas of ultracold fermions (see http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.010401). On the other hand, the work of Duncan Haldane on magnetic systems was important for our recent experiments on 1D antiferrmagnetic spin chains (see http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.115.215301).

The 2016 Nobel Prize in Physics - Press Release Nobelprize.org, The Official Web Site of the Nobel Prize

Summer has finally arrived in Heidelberg!

Last week we helped Selim set up a new business, a pizzeria! The grand opening was on April 1st.
Also we are happy to welcome our new postdoc, Philipp. This is no joke ;)

We introduced a new dress code today 😉

One formula that many of us probably remember from our physics and chemistry classes in school is the ideal gas equation PV = NkT, which relates the volume (V) and pressure (P) of a gas of N atoms to its temperature (T). It is such a simple, yet powerful formula which has helped us understand so many phenomena around us! However, it turns out it can only be used in situations when the quantum mechanical nature of particles and the interactions between them can be neglected - something that is only guaranteed at very high tempertures.

There are so many fascinating materials around us which don't satisfy these conditions, for eg. High-Tc superconductors and graphene. In these materials, not only do electrons (which are fermions) interact very strongly, they are also constrained to move in a two-dimensional plane. How do we understand the thermodynamics of such systems? We do experiments, of course! In our recent experiments, we confined a gas of fermionic atoms in a 2D plane and cooled it to temperatures only a billionth of a Kelvin above zero. We were able to measure, for the first time, the equation of state of the gas as a function of temperature and inter-atomic interaction strength. We were able to obtain a formula (similar to PV=NkT, but a bit more complicated) that can be applied to any system with similar conditions. Hopefully in the long run, this finding will help towards understanding the behavior of several fascinating phenomena like High-Tc superconductivity.

This research, done in collaboration with theorists Igor Boettcher and Tilman Enss, has been published in the recent issue of Physical Review Letters. It has also been selected for a viewpoint in Physics magazine written by Meera Parish.

Viewpoint: Journey from Classical to Quantum in Two Dimensions Two separate groups have extracted the thermodynamic equation of state for a two-dimensional gas of fermionic atoms, revealing its peculiar quantum features.

A successful year is coming to an end, we wish everyone a merry Christmas and a happy New Year. Thanks to Prof. Stachel and her group for the PI Christmas Party! And congratulations to this year's kicker champions, Mathias and Manuel!

Magnetism has fascinated and puzzled scientists for centuries. An important problem in modern physics is the quantum mechanical connection of magnetism to other exotic phenomena like high-Tc superconductivity. We want to understand this connection from a bottom up perspective.

In our recent experiments, we have created a chain of 4 fermionic ultracold atoms and observed the emergence of magnetic order in this system. For the first time, we have observed magnetism with fermionic atoms that goes beyond nearest neighbor correlations.

This work was lead by Simon Murmann and was done in collaboration with physicists from University of Hannover and University of Lund. It has been published in Physical Review Letters and has been selected as an Editor's Suggestion.

The press release of the University of Heidelberg can be found here:
https://www.uni-heidelberg.de/presse/news2015/pm20151120_quantensimulation_magnetismus.html

Antiferromagnetic Heisenberg Spin Chain of a Few Cold Atoms in a One-Dimensional Trap Quantum magnetism that goes beyond nearest-neighbor correlations has been observed in a string of four ultracold fermions.

Pictures from our recent retreat to Trifels. It was a fun trip with some hiking, camping, drinking and playing funny games :-)