Humboldt-Universität zu Berlin - Faculty of Mathematics and Natural Sciences - Physics of low-dimensional systems

2023

• December 13, 2023: We celebrate our Christmas dinner with former colleagues, friends and family. Happy holidays!

 

 

• December 12, 2023: New manuscript entitled Strain fingerprinting of exciton valley character on Arxiv.

 

In this work lead by our colleagues in the group of Kirill Bolotin at the Freie Universität Berlin we use our previously presented electrostatic straining technique to identify the valley character of the many excitonic species present in suspended TMDs at cryogenic temperatures. Our strain approach allow us to brighten otherwise dark momentum-indirect excitons with wavefunctions residing in the K, Q, and Γ valleys. We report the first experimental observation of ΓQ excitons and the largest energy tuning range for single photon emitters in WSe2. Overall, we demonstrate the possibilities of our combined optical and straining technique to probe and manipulate momentum direct and momentum-indirect excitons in suspended 2D semiconductors.

 

 

• November 23, 2023: Our new Tip-Enhanced Raman Spectroscopy system arrives from Belo Horizonte, Brazil. The PORTO scanning near-field optical microscope is the core prodcut of FabNS, a Brazilian startup of which we are proud to be the first customer.  
   
  
• November 15, 2023: Welcome back, Pietro! Dr. Pietro Marabotti joins us as a Postdoctoral researcher. He was recently awarded with an Einstein International PostDoctoral Fellowship with his project Probing nonlinearities in carbyne with undetected photons at nanoscale. Pietro obtained his PhD in Energy and Nuclear Science and Technology in the group of Prof. Carlo Casari at the Politecnico di Milano, where he studied the optical and vibrational properties of linear carbons chains.

 

• November 15 to November 16, 2023: We participate in the third FAIRmat users meeting. FAIRmat is a consortium of the Nationale Forschungsdateninfrastruktur (NFDI) with the mission of providing scientists with a FAIR data infrastructure and the skills and tools they need to make the most of it.

 

• November 14, 2023: Pietro is awarded a fourth prize at the Spitzenforschung competition organized by Humboldt Innovation and the Industrieforschung Stiftung with his pitch on a novel near-field optical microscope with entangled photons. Congratulations!

 

 

News item at the HU website (in German): https://www.hu-berlin.de/de/pr/nachrichten/november-2023/nr-231116

 

• October 19, 2023: We attended the official inauguration of the Center for the Science of Materials Berlin (CSMB) in the IRIS Research Building on Humboldt-Universität's Science Campus in Adlershof, Berlin. We were delighted to celebrate with colleagues and friends the beginning of a new and surely very succesful scientific institution in Berlin.

 

 

• October 13, 2023:  Pablo is awarded a Best Presentation Award at the IOP-HU Early Career Researcher Conference on Condensed Matter Physics for the presentation  "Strain tuning and brightening dark excitons in 2D materials". Congratulations!  

 

• October 12 to October 14, 2023: We participated in the IOP-HU Early Career Researchers Conference on Condensed Matter Physics in Liyang, China. It was a great opportunity for us to link with our collegues from the Chinese Academy of Sciences (CAS). On Monday 16 we visited the campus of the Institute of Physics (IOP) in Beijing.

 

 

• August 8, 2023: Welcome  Kaan! Kaan Yapıcı from Istanbul Technical University joins us this Autumn as a Erasmus+ intern to work on 2D Materials fabrication and characterization of plasmonic structures.

 

• August 3, 2023: We are very happy to welcome Dr. Pietro Marabotti back in our group. He will join us with an Einstein International Postdoctoral Fellowship.

 

Pietro worked with us as a visiting PhD student in Autumn 2022. After obtaining his PhD in Energy and Nuclear Science and Technology at the Politecnico di Milano in Italy, Dr. Marabotti is coming back to Berlin.

Pietro will set up a near-field scanning optical microscope that performs infrared spectroscopy using entangled photons pairs at nanoscale resolution. He will study how structural non-linearities like defects, kinks or bends affect the optical and electronic properties of confined carbyne and explore its potential for nanoscale light transduction.

Welcome back!

 

 

• March 18 to March 24, 2023: We will be taking part in the 35th International Winterschool on Electronic Properties of Novel Materials (IWEPNM) in Kirchberg am Tirol, Austria. This winter schools gives a broad overview over the physics and chemistry of carbon nanostructures, two-dimensional materials and topological systems through a series of invited talks and contributed poster presentations. We are very excited to meet many friends, colleagues and collaborators there and to engage in many fruitful discussions!

 

• January 11, 2023: New manuscript entitled Surface-Sensitive Raman Scattering by Transferable Nanoporous Plasmonic Membranes on ArXiv. 

 

It is often challenging or impossible to perform Raman spectroscopy of surfaces or thin films since their Raman signatures are very weak or obscured by the much stronger bulk Raman signal. In this work we overcome this problem by placing a thin nanoporous gold membrane on the surface of interest. The pores act as plasmonic slot antennas and enhanced the Raman signals of the surface underneath, while the membrane itself suppresses the bulk Raman signal. We improve the surface-to-bulk Raman signal ratio by three orders of magnitude show that the Raman enhancement occurs in the top few nanometers only.

 

Is this approach actually useful? Yes! We use our plasmonic membranes to study the surface of a thin film of LaNiO3, a conductive complex oxide that is an important electrode material for perovskite type heterostructures. We find a clear Raman mode splitting that is indicative of structural changes in the surface layer of the LaNiO3 film. This splitting is absent in the Raman spectra without our nanoporous membrane and has, to the best of our knowledge, not been reported before. Collaboration with between HU Berlin, Université Le Mans, and several groups from ETH Zürich.

 

Lala, Giorgia, Sebastian, and our collaborator Roman Wyss are working on making our nanoporous gold membranes generally available. Get in touch if you are interested in performing surface-sensitive Raman spectroscopy on your surface of interest!

 

 

 

2022

• December 19, 2022: Our team celebrates the Christmas dinner and cheers for the year to come. Happy holidays!

 

 

• December 15, 2022: New publication Raman spectroscopy of isolated carbyne chains confined in carbon nanotubes: Progress and Prospects has been published in Chinese Physics B. This Review is part of a special topic: The Third Carbon: Carbyne with One-Dimensional sp-Carbon edited by our collaborator Prof. Lei Shi from Sun Yat-sen University in Guangdong, China. In this review we focus on open questions in the research of confined carbyne, long linear chains of carbon inside carbon nanotubes, and how these questions can be addressed by studying single, isolated confined carbyne chains. 

 

 

• December 12, 2022: New publication Strain control of hybridization between dark and localized excitons in a 2D semiconductor has been published in Nature Communications. In this collaboration with FU Berlin and TU Wien, we electrically apply strain on a 2D semiconducting membrane of monolayer WSe2 to bring dark and localized excitons into resonance, prompting a new hybrid state that inherits the properties of the constituent species.

 

 

• November 17, 2022: Our colleague and friend, Prof. Carlo S. Casari from the Micro- and Nanostructured Materials Laboratory of the Politecnico di Milano visit us. Prof. Casari gives a seminar entitled From Carbon atomic wires to 2D structures beyond graphene.

 

 

• November 11, 2022: Giorgia and Pablo participate in the Adlershofer Forchungsforum 2022 with two posters on Surface Sensitive Raman Scattering with Au membranes and Strain control of hybridization of excitons in WSe2. Thanks to everyone who passed by for the interest and fruitful discussions!

 

 

• November 8, 2022: Our colleague and friend, Nano-Optics expert Prof. Lukas Novotny from ETH Zürich visit us. Prof. Novotny holds a colloquium on Low-Dimensional Optoelectronics at the Main Lecture Hall of the Institut.

 

• October 17, 2022: Johannes and Pablo participate in the first in person meeting of the Graduate School Advanced Materials (GS-AM) after the pandemic. They are very excited to establish personal and professional bonds with other PhD candidates in Berlin. You can also join the GS-AM here.

 

• October 10, 2022: Sebastian gives a talk presenting our research on carbyne at the Magnus-Haus Berlin to a broad audience including many students as a part of the Physics & Pizza format organized by the AGyouLeaP of the Deutsche Physikalische Gesellschaft

 

 

• September 2, 2022: Welcome Pietro! Pietro Marabotti from the Casari group at Politecnico Milano joins us as a visiting PhD student until the end of 2022 to work on polyynes and confined carbyne.

 

 

• July 25, 2022: New manuscript entitled Strain control of hybridization between dark and localized excitons in a 2D semiconductor on ArXiv. In this work we controllably strain monolayer WSe2 membranes at cryogenic temperatures to tune the energy alignment between excitonic species. In this way we bring free dark excitons and localized defect-related excitons together to form a hybridized state that dominates the photoluminiscence response of the material and from which single photon emission likely takes place. Fruitful collaboration with the group Kirill Bolotin at Freie Universität Berlin and the group of Florian Libisch at TU Wien.

 

• July 14, 2022: Pablo is awarded the Physik-Studienpreis 2022 by the Physikalische Gesellschaft zu Berlin for his master's degree in Physics at FU Berlin. Congratulations!  

 

 

• June 27, 2022: Sebastian gives a talk on "How to build a career in academia" at the Working in Photonics Conference in Berlin.

 

 

• June 21, 2022: Sebastian gives a talk on "Raman spectroscopy of single carbyne chains confined in CNTs" at the 22nd International Conference on the Science and Applications of Nanotubes and Low-Dimensional Materials.

 

• June 17, 2022: Pablo presents the group and gives the talk "Strain engineering and hybridization of excitons in 2D semiconductors" at the Friday Light Talks in the main lecture hall of the Lise-Meitner-Haus. Afterwards we shared some beers and very interesting discussions with our colleagues.

 

 

• June 15, 2022: Pablo was elected today along with our friend Laura Orphal-Kobin as representatives for IRIS junior scientists. They will represent the interests of PhD-students, postdocs and students at the IRIS council and they will also have the support of the IRIS administration to organize scientific and socializing events. Please contact them for any requests/suggestions!

 

• June 3, 2022: We celebrate the joining of Lala and Giorgia to our group and the visit of our collaborator Dr. Roman Wyss to kick-start MetaMem project with a barbecue in front of the Institut. 

 

• June 1, 2022: Welcome, Lala and Giorgia! Lala Habibova and Giorga Marcelli join our group as new team members. Lala and Giorga participate in the AdMaLab program by the Innovation Network for Advanced Materials, a Berlin-based incubator program to promote researchers and young startups that aim to find commercial use for new and advanced materials. Within Team MetaMem, Lala and Giorgia aim to use porous Au membranes for SERS based flow-through sensing and to reveal new material properties. They will be mentored by Sebastian and our collaborator Dr. Roman Wyss from Zürich, Switzerland.

 

• March 31, 2022: New publication Freestanding and Permeable Nanoporous Gold Membranes for Surface-Enhanced Raman Scattering has been published in ACS Materials & Interfaces. In this joint work between HU Berlin, IBM Research Rüschlikon and the Photonics Lab at ETH Zürich, we use graphene to show that single nanoscale pores in suspended and mechanically stable porous gold membranes support plasmon-enhanced Raman scattering with enhancements of the order 10^5 at high excitation powers.

 

 

• March 18, 2022: We are happy to announce that we received funding by the Akademischer Senat der Humboldt Universität Berlin within an initiative to foster digital media in research and teaching. We will integrate modern optical experiments located in our labs into teaching by performing them live per remote control from the lecture hall – exciting!

 

2021

• December 8, 2021: We are happy to announce that the PLD group joins IRIS Adlershof as a Junior Member.

 

• November 8, 2021: Our PhD student Johannes was admitted in the Graduate School "Advanced Materials".

 

• October 27, 2021: The PLD group takes part in an open seminar about Milestones of Quantum technology with participants from around the world where we discuss important papers for Quantum Technology. Get in touch by email if you want join, Wednesdays 16.15 to 17.45.

 

• October 5, 2021: Sebastian gives a talk at the Integrative Reseach Institute for Science (IRIS) of Berlin on Exploring Confined Carbyne.

 

• October 3, 2021: Welcome to Berlin, Gétulio! Gétulio Silva e Souza Júnior from the Universidade Federal do Rio de Janeiro in Brazil joins our group as a project student.

 

• October 1, 2021: Welcome Johannes! Johannes Lechner from the Ludwig-Maximilians-Universität Munich joins our group as a PhD student.

 

• September 27, 2021: New manuscript entitled Freestanding and permeable nanoporous gold membranes for surface-enhanced Raman scattering on ArXiv. In this work we use graphene to show that single nanoscale pores in suspended porous gold membranes support plasmon-enhanced Raman scattering with enhancements of the order 10^5 at high excitation powers.

 

• July 13, 2021: New publication. Anti-Stokes Raman Scattering of Single Carbyne Chains has been published in ACS Nano.

 

• July 8, 2021: Our PhD student Pablo was admitted in the Graduate School "Advanced Materials".

 

• May 1, 2021: Welcome Pablo! Pablo Hernández López from the Freie Universität Berlin joins our group as a PhD student.

 

• March 17, 2021: Sebastian takes part in the HU Optics Spring Meeting 2021 with his talk Exploring confined carbyne.

 

• March 1, 2021: Our group is born! Dr. Sebastian Heeg joins the Institut für Physik of the Humboldt University as the leader of the Emmy-Noether-Group PLD (Physics of Low Dimensional systems) with the project Carbyne for Optoelectronics and Optomechanics.