In our research group (abbreviated NS2) we study electronic transport in quantum matter systems and especially the dynamics of such systems. Our current research includes the dynamics of SNS or SFS junctions (S=superconductor, N=normal metal, F=ferromagnet), non-Gaussian high frequency quantum noise, (non-equilibrium) spin dynamics and spin-dependent thermoelectric effects in superconductors, atomic scale shot-noise as well as unconventional superconducting proximity effects in micro-magnetic systems.

NS2 is part of the Laboratoire de Physique des Solides (LPS, Solid State Laboratory), a laboratory under the joint management of the Centre National de Recherche Scientifique (CNRS) and the Université Paris-Sud. We are located on the Saclay plateau in Orsay, approximately 30km south-west of Paris.

We are always happy to talk to bright and motivated students interested in internships, PhD positions or postdocs. Some ideas for internships or projects can be found here. Please feel free to contact us.


Here are M2 internships proposals for the season 2018-2019:

Time reversal breaking in a transmon molecule:

The realization of artificial lattices with broken time reversal symmetry is a very active field of research in condensed matter, ultracold atoms and photonics. The long term objective of our team is to realize such lattices for microwave photons using the tools of circuit QED. A first step in this direction is the study of a molecule formed by a ring of three transmons as shown in the figure (a). In the absence of external fields, the first two excited states of the molecule, which correspond to two states with opposite angular momentum, are degenerate. But, as shown in the figure (b), applying both an electric and a magnetic field to the molecule lifts the degeneracy and breaks time reversal symmetry [1]. The aim of this internship will be to confirm these calculations and to design a circuit to observe this effect. We will then fabricate the circuit and confirm experimentally that the first two excited states carry orbital angular momentum.

(a) Scheme of the transmon molecule formed by a ring of three Josephson junctions. (b) Preliminary calculation of the molecule spectrum as a function of the magnetic flux through the ring in the presence of electric field (Vg ≠ 0). The dashed line shows a possible working point where the degeneracy between the first two excited states (orange and green lines) is lifted. The goal of the internship will be to prove theoretically and experimentally that these two states carry opposite angular momentum.

[1] J. Koch, A. Houck, K. Le Hur and S.M. Girvin Phys. Rev. A 82, 043811 (2010).

Contacts: Jérôme Estève, Julien Gabelli
jerome.esteve@u-psud.fr, julien.gabelli@u-psud.fr
Phone number: +33 1 69 15 53 65

Atomic scale shot-noise of a superconductor:

Many interesting properties in condensed matter systems originate from interactions between electrons. Since these interaction usually take place on short timescales, a measurement of time-averaged properties is often missing crucial information. In order to gain access to interactions and electron dynamics we have recently developed a scanning tunnelling microscope that can measure current fluctuations with atomic scale spatial precision. In this project you will use this system to investigate electron correlations and dynamics in superconductors.

One of the questions we are interested in is what happens when a defect or impurity is introduced to a superconductor, especially when the impurity is magnetic, meaning it has a nonzero spin? Two processes can occur in this case: (1) the spin is screened by electrons with opposite spin that hop on and off the site, a quantum mechanical process called Kondo screening, or (2) the spin is not (or insufficiently) screened and acts as a pair-breaking potential leading to one or more states inside the superconducting excitation gap. The latter case is particularly interesting as the single spin is protected from scattering or decoherence by the superconducting excitation gap, in principle allowing one to drive the spin and study spin dynamics at the atomic scale.


Shot-noise scanning tunnelling microscopy. (a) Home-built microscope with circuitry implemented, allowing us to (b) measure shot-noise at low temperature, (c) the electron temperature and (d) differential conductance at 1MHz.

Contacts: Freek Massee, Marco Aprili
freek.massee@u-psud.fr, marco.aprili@u-psud.fr
Phone number: +33 1 69 15 37 90

Resolving microwave photon numbers with high impedance resonators:

The detection of single microwave photons has been a long standing goal in microwave quantum optics for the past decade. The challenge is greater than in the optical regime, since a single microwave photon carries 5 orders of magnitude less energy than an optical photon. Different complex scenarios have already been implemented all using low impedance microwave cavities and superconducting qubits.

In this internship we propose to use a novel type of detection mechanism. It relies on the newly developed high kinetic inductance coplanar waveguide resonator that enhances the ac-voltage created by a single photon. Coupling the resonator to a metallic island will result via highly efficient photon-assisted processes in the appearance of an extra-charge on the island measurable with a single electron transistor in near proximity. The high impedance resonator will consist in high kinetic inductance superconducting nanowires that have been developed in the group either in tungsten [1] or granular aluminum.

The student will use finite element simulations to model the coupled system, fabricate the sample using state-of-the-art electron beam lithography and metal evaporation and measure at very low temperature (10mK) the fabricated sample in a dilution refrigerator.

(a) Detection scheme proposed to detect single microwave photons using a high impedance resonator. (d) Scanning electron microscope picture of a tungsten nanowire exhibiting a very high kinetic inductance necessary to increase the detection efficiency.

[1] Non-linear Hybrid Microwave Resonators Made by He-Beam Assisted Deposition of Tungsten Nanowires. J. Basset, D. Watfa, G. Aiello, M. Fechant, A. Morvan, J. Esteve, J. Gabelli, M. Aprili, R. Weil, A. Kasumov, H. Bouchiat and R. Deblock. arXiv:1811.06496 (2018).

Contacts: Jérôme Estève, Julien Basset
jerome.esteve@u-psud.fr, julien.basset@u-psud.fr
Phone number: +33 1 69 15 53 65

Research

People

Publications

November 2017
Cyril Vaneph has successfully defended his thesis.

October 2017
Freek Massee has started as a 'Chargé de Recherche' with the CNRS. He remains in the group.

June 2017
Aymeric Courilleau and Baptiste Jost have joined us as interns.

April 2017
Félicien Appas has joined us as an intern.

March 2017
Charis Quay has been awarded a Bronze Medal by the CNRS.

January 2017
Pierre Février has successfully defended his thesis.

September 2016
Marko Kuzmanović and Gianluca Aiello have joined the group as PhD students.

June 2016
Nikhita Baladari has joined us as an intern.

May 2016
Faten Ben Chaabane, Alexander Noddings and Mohamed Ouerfelli have joined us as interns.

March 2016
Marko Kuzmanović has returned to the group as an intern.

February 2016
Bi Yi Wu is visiting from the National Taiwan University for six months.

October 2015
Mathieu Féchant has started his PhD in the group.

September 2015
Alexis Morvan has started his PhD and Gianluca Aiello has joined as an intern.

July 2015
Julien Basset and his colleagues at ETH Zurich published in PRL.

June 2015
Pierre Chevalier and Clément Leroy have joined as interns.

May 2015
Charles Rigoudy has joined as an intern.

April 2015 Our work on spin resonance of quasiparticles in superconducting aluminium has been published in Nature Communications.

February 2015
Freek Massee has joined the group as a postodoc.

January 2015
Cyril Vaneph has joined as a PhD student. Alexis Morvan and Mathieu Féchant have joined as interns.

October 2014
Jérôme Estève has joined the group. Marko Kuzmanović has joined as an intern.

September 2014
Julien Basset has joined the group. Maximilian Weideneder will be spending the academic year with us as part of his diplomarbeit. Tom Dvir is visiting us and the Mesoscopic Physics group for a few weeks.

August 2014
Our work on the spin (imbalance) lifetime in a superconductor in the frequency domain is published. Experiment, Theory.

May 2014
Yann Chiffaudel has joined as an intern. Christoph Strunk is visiting the group.

April 2014
Jordan Bouaziz has joined as an intern.

January 2014
Tito Williams has joined as a visitor.

November 2013
Our work on a third-order correlator of the electromagnetic field is published in New Journal of Physics, arXiv.

October 2013
Pierre Février has started his PhD in the group.

February 2013
We have shown that it is possible to control the shot noise across a tunnel junction using high-frequency 'biharmonic illumination' arXiv, Nature Physics.

January 2013
Baydir Bouali and Pierre Février have joined as interns, Edouard Pinsolle as a postdoc.

August 2012
We have shown that it is possible to have spin imbalance but not charge imbalance (and vice versa) arXiv, Nature Physics, News and Views.

July 2012
Marco Aprili will be on sabbatical this coming academic year at Cornell University.