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Exciton fission – one photon in, two electrons out

Exciton fission one photon in two electrons out
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Poster by David Gauthier at GDR UP 2022

David Gauthier presents a poster at the GDR U.P. event.

The “Ultrafast Phenomena” Research Group GDR n° 3754 (U.P.) studies matter on ultrashort time scales.

The GDR U.P. began on January 1, 2016. It brings together the French community of experimenters and theoreticians interested in phenomena on the Attosecond, Femtosecond and Picosecond time scales and operating in all states of matter (diluted medium, solid, nanometric, liquid and plasma).

The GDR. U.P. brings together more than 800 participants, for more than 100 research teams distributed in more than 50 laboratories throughout France. A club of industrial partners collaborates with the GDR U.P. This club brings together around ten industrialists who support our activities.

The GDR. U.P works to bring together French teams and promote our community, constantly providing an overview of “ultra-rapid” activity in France in order to highlight our strengths, our actions, our usefulness and our needs.

The GDR. U.P is managed by an office which brings together 18 members of the French ultrafast community.

The GDR. U.P also supports the club of young scientists in ultra-rapid sciences.

Reference Link

 

To obtain comprehensive and up-to-date information concerning our diverse range of events, we cordially invite you to consult our dedicated “News and Events” page.

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OPTOLOGIC meets at Benasque for the CGA meeting

OPTOlogic CGA Meeting

The European OPTOlogic project held its first in-person CGA meeting in Benasque, Huesca, at the “Pedro Pascual” Science Center on March 9th and 10th, 2023. Notably, ICREA Professor of ICFO Dr. Jens Biegert and project manager Judith Salvador from ICFO organized the successful meeting to unite the entire project consortium. The primary objectives of the meeting were threefold: first, to share updates on each work unit’s current status and progress; second, to present and learn about the diverse results and latest advancements; and finally, to foster discussions to exchange ideas and find solutions to complex challenges in the project’s final stages.

Furthermore, this CGA meeting marked a significant milestone as the consortium’s first in-person gathering since the project began in September 2020. The productive two-day event provided a valuable platform for consortium members to engage in discussions and collaboratively address potential theoretical and experimental changes. Consequently, these in-depth conversations and collaborative efforts were crucial for ensuring the project’s continued success and advancement towards its ultimate goals. Moreover, the meeting fostered a sense of community and renewed motivation among the participants, who departed with a clearer vision for the project’s remaining tasks. In addition, the picturesque setting of Benasque further enhanced the collaborative atmosphere, providing a serene environment for focused discussions and the exchange of innovative ideas.

 

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CGA Meeting in Benasque

OPTOlogic project meeting in Benasque

From March 9 to 10, the CGA meeting of the European OPTOlogic project will take place in Benasque, Huesca, at the “Pedro Pascual” Science Center.

ICREA Professor Dr. Jens Biegert and project manager Judith Salvador from ICFO are leading this gathering to bring together all members of the project consortium. They are orchestrating an inclusive forum to provide a comprehensive update on the current status and progress of each work unit within the project framework. The meeting will also showcase and explore the various results and latest advances the project has achieved. Additionally, the event aims to foster meaningful discussions, promote idea exchange, and collaboratively seek solutions for any challenges that may arise during the final phase of the project’s execution. This meeting is particularly important because it marks the first in-person gathering since the project’s inception in 2020. As stakeholders eagerly anticipate this momentous occasion, the first in-person gathering since the project’s inception, it presents an invaluable opportunity to reinforce collaborations, forge new partnerships, and collectively propel the OPTOlogic Project towards its envisioned success.

Stay informed about this event and other upcoming engagements by regularly visiting our ‘News & Events‘ section. Don’t miss out on the latest happenings within the OPTOlogic European Project!

OPTOlogic European Project Meeting
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Jens Biegert – Optica Board of Directors

Jens Biegert joins Optica Board of Directors
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Generation of many-body Bell correlated states in optical lattices

Many-body Bell correlated states in optical lattices

OPTOlogic researchers from ICFO, in collaboration with the University of Warsaw and the Institute of Physics, Polish Academy of Sciences, show how to generate many-body Bell correlated states using ultracold quantum gases in optical lattices. 

Quantum Correlations and Their Significance

Quantum correlations are a fundamental aspect of quantum mechanics. They refer to the correlations between the outcomes of measurements performed on two or more particles in a quantum system. These correlations can exhibit strange and counterintuitive behaviors not present in classical systems.

Entanglement and Bell Correlations

The phenomenon of entanglement exemplifies quantum correlations. It describes the correlation between two or more particles, a property that classical physics cannot explain. For example, if two particles entangle, the outcome of the measurement performed on one particle can predict the state of the other, even if the particles are separated by large distances. Bell correlations offer another example, referring to correlations between the outcomes of measurements performed on two or more particles that any local hidden variable theory cannot explain. These correlations often demonstrate the non-classical nature of quantum mechanics and the limitations of classical theories.

Quantum Correlations in Quantum Technologies

Quantum correlations play a key role in developing quantum technologies that exploit the unique properties of quantum systems to perform tasks not possible using classical technologies, including quantum teleportation, quantum cryptography, and quantum computing. However, the generation of many-body Bell correlated states, especially those implemented during the One-Axis Twisting protocol (OAT) procedure, posed an open question for science until now.

Breakthrough in Generating Many-Body Bell Correlated States

In an international study published in Physical Review Letters, ICFO researchers Dr. Marcin Płodzień (also NAWA Bekker 2020 Fellow) and ICREA Prof. Maciej Lewenstein, in collaboration with Prof.Jan Chwedeńczuk from the University of Warsaw and Prof. Emilia Witkowska from the Institute of Physics, Polish Academy of Sciences, have shown that massively correlated quantum many-body states could be generated through current ultracold bosons in optical lattices experiments, using the One-Axis Twisting protocol (OAT) known for generating spin squeezed states.

Spin squeezing states

While entanglement shows how correlated particles can be, spin squeezing is a phenomenon that occurs in a system of particles with a shared quantum state, such as a group of atoms or ions. It involves decreasing as much as possible the uncertainty in the measurement of one of the observables, or “spin” variables, at the expense of increasing the uncertainty in the measurement of the other variables involved.

One-Axis Twisting Protocol (OAT) for Spin Squeezed States

One of the most well-known methods for generating squeezed entangled states is the one-axis twisting protocol (OAT). It can be implemented using various ultra-cold systems interacting through collisions or atom-light interactions and it was well understood that it creates many-body entangled states and two-body Bell correlations.

Novel Insights from the Research

Researchers showed that the one-axis twisting also serves as a viable resource for powerful many-body Bell correlations. They presented a systematic analytical study of creating many-body Bell-correlated states during one-axis twisting dynamics in two-component bosonic systems. They provided the critical time at which the many-body Bell correlations emerge together with a simple yet powerful formula for characterizing the depth of the Bell correlations and entanglement, then applied these findings to classify the generation of many-body Bell correlations in systems of two-component bosons loaded into a one-dimensional optical lattice.

Practical Implications of the Study

The results of this study show that current technology can create such correlations. This holds great importance for potential applications, as Bell correlations can boost the precision of quantum sensors or improve the security of quantum cryptography protocols. Creating such ultra-non-classical many-body states holds fundamental relevance, especially in light of the recent Nobel prize awarded for pioneering studies of such phenomena.

 

Cited article: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.129.250402

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Article presentation by Peng Ye at EPJ Web of Conferences 2022

 

© The Authors, published by EDP Sciences, 2022

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

MoS2 band structure
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Misha Ivanov invited to ICFO to give a talk about Attosecond control of electron dynamics in simple and strongly correlated materials

As part of the Light for Graphene (L4G) seminars on December 12th, 2022, ICFO welcomed Mikhail Ivanov, who delved into processes associated with electron dynamics in correlated materials. Professors Maciej Lewenstein and Jens Biegert graciously hosted the session. Below, you’ll find details encompassing the abstract of the discussion alongside Dr. Ivanov’s professional trajectory.

Abstract:

Attosecond spectroscopy and strong light fields boldly embarked into solid-state physics about a decade ago.

Throughout this decade, we have come to appreciate that strong light fields drive electrons in solids not solely on the time-scale of the pulse envelope but also on the sub-cycle time scale. This control over light oscillations and polarization at the sub-cycle level presents intriguing opportunities to manipulate electronic responses on a sub-femtosecond time scale. Furthermore, I will exemplify these opportunities with a series of cases, ranging from PHz valleytronics in graphene to attosecond spectroscopy of the 2D Hubbard model.

Should time permit for the preparation of new slides, I intend to shift the focus entirely towards discussing our latest findings. These findings delve into resolving the mystery of insanely fast 1 fsec dephasing times in strongly driven solids and probing the enigmatic behavior of not-so-massless, massless Fermions in Weyl semimetals.

Biography:

Education and Early Career

Mikhail Ivanov heads the Theory Department at Max Born Institute and also holds a Professor position in the Department of Physics at Humboldt University.

Born in the USSR and educated at Moscow State University, Misha left Moscow within a year after the USSR ceased to exist.

International Work Experience

Since then, he has worked extensively in Canada, Poland, the UK, and Germany. Currently, he leads the Department of Theory at the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy in Berlin, alongside his professorship at Humboldt University Berlin.

Current Positions and Affiliations

Despite his global journey, Misha maintains his professorial role at Imperial College London due to his fondness for the city. Additionally, he holds a visiting professor appointment at the Technion in Haifa, Israel, reflecting his deep affection for the country.

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Optologic Partner Misha Ivanov – ICFO talk

L4G SEMINAR at ICFO

MIKHAIL IVANOV: Attosecond control of electron dynamics in simple and strongly correlated materials

On December 12th, 2022, Mikhail Ivanov came to give a talk to ICFO about the processes related to electron dynamics in correlated materials. Below, details of the abstract and Dr. Ivanov’s professional path.

Abstract:

Attosecond spectroscopy and strong light fields boldly ventured into solid state physics about a decade ago. In the years since then, we have learned to appreciate that strong light fields drive electrons in solids not on the time-scale of the pulse envelope, but rather on the sub-cycle time scale. Furthermore, control over light oscillations and light polarization on the sub-cycle scale opens the opportunities to control the electronic response on sub-femtosecond time-scale. To illustrate this point, I will provide a series of examples, ranging from PHz valleytronics in graphene to attosecond spectroscopy of the 2D Hubbard model.

However, in the unlikely event that I have enough time to prepare new slides for this talk, I will change it completely. Instead, I will discuss our latest results on resolving the mystery of insanely fast 1 fsec dephasing times in strongly driven solids and the very puzzling behavior of not so massless, massless Fermions in Weyl semimetals.

Biography: 

Mikhail Ivanov is Head of the Theory Department at Max Born Institute and Professor of the Department of Physics at Humboldt University.

Born in the USSR and educated in Moscow State University, Misha left Moscow within a year after the USSR ceased to exist.

Since then, he has worked in Canada, Poland, UK, and Germany, where he now heads the Department of Theory at the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy in Berlin, together with professorship at the Humboldt University Berlin.

Because Misha likes London, he still manages to keep his professor appointment at the Imperial College London, and because Misha loves Israel, he is also partially localized at the Technion in Haifa, where he now holds a visiting professor appointment.

Hosted by ICFO Professors Maciej Lewenstein and Jens Biegert.
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High Harmonic spectroscopy unveils the phase transitions of high-temperature superconductors

Researchers from ICFO, ICMAB-CSIC and Guangdong Technion-Israel Institute of Technology have developed a new methodology to investigate and measure the quantum phase transitions of a high-temperature superconductor by using High Harmonic spectroscopy.

Exploring Superconductors

Superconductors are materials that exhibit the ability to conduct electricity without any resistance. This phenomenon occurs in materials when they cool below the so-called superconductor transition temperature, often at very low temperatures (a few degrees above absolute zero). Among these materials are the so-called high-temperature superconductors, which function as superconductors at temperatures above 77K (the boiling point of liquid nitrogen). Researchers have found these materials to be crucial in developing new electronic and information processing devices, as well as optical quantum computers, and even in improving the efficiency of electrical transmission lines.

Challenges in Understanding High-Temperature Superconductivity

However, scientists have observed that high-temperature superconductivity closely relates to controlling their microscopic dynamics. So far, detecting the various microscopic quantum phases in these complex materials has proven quite challenging. Not only do these dynamic states have incomplete physical processes due to their wide array of quantum states, but the current methods used to explore their dynamics at microscopic scales lack sensitivity. Therefore, researchers need new tools to better understand the dynamic evolution of these types of superconductors.

Now, in an international study, ICFO researchers Utso Bhattacharya, Ugaitz Elu, Tobias Grass, Piotr T. Grochowski, Themistoklis Sidiropoulos, Tobias Steinle, and Igor Tyulnev, led by ICREA Professors Jens Biegert and Maciej Lewenstein, in collaboration with ICMAB-CSIC researchers Jordi Alcalà and Anna Palau, and Marcelo Ciappina, from the Guangdong Technion-Israel Institute of Technology, proposed a new methodology based on the use of High Harmonic spectroscopy (HHS) to investigate the transitions between the different phases of  YBCO, a copper oxide cuprate material which is a well-known high-temperature superconductor. This study represents a major scientific breakthrough since it is the first time that highly non-linear and non-perturbative diagnostics/detection methodology is used to understand the behavior of strongly correlated materials.

Experimental and Theoretical Innovations

In light of the experimental results, the researchers surpassed expectations and presented a new theoretical model to identify the connection between the measured optical spectra and the transition between the different quantum states of YBCO: strange metal, pseudogap, and superconductor. The study, recently published in the journal PNAS, showcases their findings.

In their experiment, the researchers used 100nm thick films of YBCO mounted on a micro-refrigerator. They first characterized the superconducting properties of the YBCO films and confirmed their quality. Then, using ultra-short infrared laser pulses, they induced high harmonics generation in the material samples, which they placed inside a vacuum chamber and cooled to a temperature of 77K.

High Harmonics are the high-energy photons emitted by the electrons of a system when it experiences a strong laser field. These emitted photons have a frequency many times that of the driving laser field.

Upon hitting the surface, they recorded the reflected radiation with a spectrograph to study the harmonic spectrum. This spectrum contains the imprints of this nonlinear optical response and has a connection with the phase transitions.

Theoretical Modeling

Observing these experimental results in the lab and the absence of a theory that could explain what they were observing, the researchers developed a new strong-field quasi-Hubbard model to shed light on the connections between the measured high harmonics and the formation of Cooper pairs, that is, the paired electrons responsible for the superconducting phase.

When applying this new theoretical model, the theoretical calculations of the high harmonic spectra obtained matched the experimental data. “The model faithfully reproduces the functional form of the measurement data over the entire temperature range and for several orders of magnitude of harmonic amplitude,” the authors highlighted. This new approach, as they noted, has allowed a theoretical connection between the measurements and the underlying microscope dynamics, providing a “powerful new methodology to study the quantum phase transitions” in correlated materials.

Finally, the team emphasizes that their work offers a “first striking example” of how High Harmonic Spectroscopy can distinguish correlated phases of matter. They also believe that it paves the way for a “refined understanding of the physical processes occurring inside high-temperature superconductors”.

Acknowledgements

We thank V. Kunets from MMR Technologies and X. Menino at Institut de Ciencies Fotoniques for technical support and Dr. K. Dewhurst and Dr. S. Sharma for help with the ELK code. J.B., U.E., T.P.H.S., T.S., and I.T. acknowledge financial support from the European Research Council (ERC) for ERC Advanced Grant “TRANSFORMER” (grant 788218) and ERC Proof of Concept Grant “miniX” (grant 840010). J.B. and group acknowledge support from FET -OPEN “PETACom” (grant 829153), FET-OPEN “OPTOlogic” (grant 899794), EIC-2021-PATHFINDEROPEN “TwistedNano” (grant 101046424), Laserlab-Europe (grant 654148), Marie Sklodowska-Curie ITN “smart-X” (grant 860553), Plan Nacional PID-PID2020-112664GB-I00-210901, AGAUR for 2017 SGR 1639, “Severo Ochoa” (grant SEV-2015-0522), Fundació Cellex Barcelona, the CERCA Programme/Generalitat de Catalunya, and the Alexander von Humboldt Foundation for the Friedrich Wilhelm Bessel Prize. U.B., T.G., P.T.G., and M.L. acknowledge funding from the ERC for ERC Advanced Grant NOQIA; Agencia Estatal de Investigación (R&D project CEX2019-000910-S, funded by MCIN/AEI/10.13039/501100011033, Plan National FIDEUA PID2019-106901GB-I00, FPI, QUANTERA MAQS PCI2019-111828-2, Proyectos de I+D+I “Retos Colaboración” RTC2019-007196-7); Fundació Cellex; Fundació Mir-Puig; Generalitat de Catalunya through the CERCA program; AGAUR grant 2017 SGR 134; QuantumCAT U16-011424, cofunded by ERDF Operational Program of Catalonia grant 2014-2020; EU Horizon 2020 FET-OPEN OPTOLogic (grant 899794); National Science Centre, Poland (Symfonia grant 2016/20/W/ST4/00314); Marie Skłodowska-Curie grant STREDCH 101029393; “La Caixa” Junior Leaders fellowships (ID100010434); and EU Horizon 2020 under Marie Skłodowska-Curie grant agreement 847648 (LCF/BQ/PI19/11690013, LCF/BQ/PI20/11760031, LCF/BQ/PR20/11770012, and LCF/BQ/PR21/11840013). P.T.G. acknowledges the Polish National Science Center grants 2018/31/N/ST2/01429 and 2020/36/T/ST2/00065 and is supported by the Foundation for Polish Science. Center for Theoretical Physics of the Polish Academy of Sciences is a member of the National Laboratory of Atomic, Molecular and Optical Physics. A.P. and J.A. acknowledge support from the Spanish Ministry of Economy and Competitiveness through the “Severo Ochoa” Programme for Centres of Excellence in R&D (grant SEV-2015-0496), SuMaTe project (RTI2018-095853-B-C21) cofinanced by the European Regional Development Fund, and the Catalan Government grant 2017-SGR-1519. Supported by EU COST action NANOCOHYBRI CA16218. M.C. acknowledges financial support from the Guangdong Province Science and Technology Major Project (Future functional materials under extreme conditions – 2021B0301030005).
We also acknowledge the Scientific Services at Institut de Ciència de Materials de Barcelona and ICN2.
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