ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT wigner.hun-ren.hu>]

SZFI SeminarGali ÁdámHUN-REN Wigner FK SZFIAdvances in materials processing 
for quantum sensingTuesday, 9 December 2025, 10:00, KFKI Telephely, I. épület 
1. emeleti Tanácsterem Quantum sensors exploit the quantum states of atoms, 
ions, photons, spins, or solid-state defects to detect extremely small 
changes in magnetic and electric fields, temperature, pressure, rotation, 
forces, time, or chemical environments. Their exceptional performance arises 
because quantum states are highly sensitive to external perturbations and can 
be controlled and read out with remarkable precision. In this talk, I will 
present recent progress in solid-state defect–based quantum sensors achieved 
in my research group.The most established platform is the negatively charged 
nitrogen-vacancy (NV⁻) center in diamond, which exhibits excellent coherence 
and optical properties in bulk at room temperature. Its electron spin can be 
initialized and read out optically using optically detected magnetic 
resonance (ODMR) under green illumination [1,2]. However, these favorable 
properties deteriorate when NV centers are engineered close to the diamond 
surface for sensing applications. Despite decades of effort within the NV 
community, the simultaneous optimization of surface chemistry and 
near-surface defect creation remains a major unsolved challenge.We have shown 
through first-principles calculations and quantum-mechanical modeling that 
the introduction of NV centers by ion implantation and annealing inevitably 
leaves residual vacancies and vacancy clusters that act as hole sources under 
the green laser used for NV excitation. These holes are rapidly captured by 
negatively charged NV centers, converting them into their neutral charge 
state and suppressing ODMR contrast [3,4]. Our simulations indicate that this 
effect can be mitigated by raising the Fermi level near the surface using 
appropriate surface terminations, such as fluorination [5]. However, the 
experimental development of such methods is ongoing [6]. A further limitation 
of the diamond NV platform is that green illumination causes autofluorescence 
and heating in biological environments, motivating the search for alternative 
quantum sensors for bio-related applications.For more than a decade, our 
first-principles studies have suggested that neutral divacancy defects in 
silicon carbide (SiC) could provide such an alternative [7,8]. These defects 
can be excited in the infrared and emit in the second biological window, 
making them intrinsically attractive for biological sensing. Indeed, specific 
divacancy and divacancy-related color centers—such as the PL6 center—have 
been demonstrated to possess ODMR and spin properties comparable to those of 
the NV center in diamond [9]. The next step is to engineer the SiC surface 
and introduce shallow divacancy species suitable for nanoscale sensing. Under 
ambient conditions, however, SiC readily oxidizes and forms a high density of 
optical and paramagnetic defects at the interface, necessitating new 
materials-processing strategies [10]. We have shown with first-principles 
calculations that the ODMR contrast of divacancy centers can be enhanced 
through strain engineering [11], a prediction verified experimentally by our 
collaborators. Additionally, we proposed replacing the native oxide with 
carbon-chain terminations to prevent oxidation. Our simulations revealed that 
such surfaces serve as ideal hosts for shallow divacancy quantum sensors 
capable of detecting external paramagnetic species [12]. This theoretical 
proposal has since been experimentally demonstrated by our collaborators, 
paving the way toward non-invasive, room-temperature quantum sensor 
devices.[1] The nitrogen-vacancy colour centre in diamond, Marcus W Doherty, 
Neil B Manson, Paul Delaney, Fedor Jelezko, Jörg Wrachtrup, Lloyd CL 
Hollenberg, Physics Reports, 528, 1 (2013).[2] Ab initio theory of the 
nitrogen-vacancy center in diamond, Adam Gali, Nanophotonics, 8, 1907 
(2019).[3] The Role of Electrolytes in the Relaxation of Near-Surface Spin 
Defects in Diamond, Fabian A. Freire-Moschovitis, Roberto Rizzato, Anton 
Pershin, Moritz R. Schepp, Robin D. Allert, Lina M. Todenhagen, Martin S. 
Brandt, Adam Gali, and Dominik B. Bucher, ACS Nano, 17, 10474 (2023).[4] 
Controlled Surface Modification to Revive Shallow NV- Centers, Jeffrey Neethi 
Neethirajan, Toni Hache, Domenico Paone, Dinesh Pinto, Andrej Denisenko, 
Rainer Stöhr, Péter Udvarhelyi, Anton Pershin, Adam Gali, Joerg Wrachtrup, 
Klaus Kern, and Aparajita Singha, Nano Letters, 23, 2563 (2023).[5] The 
proper surface termination for luminescent near-surface NV-centres in 
diamond, Moloud Kaviani, Peter Deák, Bálint Aradi, Thomas Frauenheim, Jyh-Pin 
Chou , and Adam Gali, Nano Letters, 14, 4772 (2014).[6] Diamond surface 
functionalization via visible light-driven C-H activation for nanoscale 
quantum sensing, Lila V. H. Rodgers, Suong T. Nguyen, James H. Cox, Kalliope 
Zervas, Zhiyang Yuan, Sorawis Sangtawesin, Alastair Stacey, Cherno Jaye, 
Conan Weiland, Anton Pershin, Adam Gali, Lars Thomsen, Simon A. Meynell, 
Lillian B. Hughes, Ania C. Bleszynski Jayich, Xin Gui, Robert J. Cava, Robert 
R. Knowles, and Nathalie P. de Leon, Proceedings of the National Academy of 
Sciences, 121, e2316032121 (2024).[7] Feature Article: Time-dependent density 
functional study on the excitation spectrum of point defects in 
semiconductors, Adam Gali, physica status solidi b, 248, 1337 (2011).[8] 
Near-infrared luminescent cubic silicon carbide nanocrystals for in vivo 
biomarker applications: an ab initio study, B. Somogyi, V. Zólyomi, and Adam 
Gali, Nanoscale, 4, 7720 (2012).[9] Room temperature coherent manipulation of 
single-spin qubits in silicon carbide with a high readout contrast, Qiang Li, 
Jun-Feng Wang, Fei-Fei Yan, Ji-Yang Zhou, Han-Feng Wang, He Liu, Li-Ping Guo, 
Xiong Zhou, Adam Gali, Zheng-Hao Liu, Zu-Qing Wang, Kai Sun, Guo-Ping Guo, 
Jian-Shun Tang, Hao Li, Li-Xing You, Jin-Shi Xu, Chuan-Feng Li, Guang-Can 
Guo, National Science Review 9, nwab122 (2022).[10] Interview with Adam Gali 
in Nature Materials, 24, 996 (2025) by Anna Pertsova and Amos Martinez [11] 
Editor's suggestion: Strain-Enhanced Spin Readout Contrast in Silicon Carbide 
Membranes, Haibo Hu, Guodong Bian, Ailun Yi, Chunhui Jiang, Junhua Tan, Qi 
Luo, Bo Liang, Zhengtong Liu, Xinfang Nie, Dawei Lu, Shumin Xiao, Xin Ou, 
Ádám Gali, Yu Zhou, and Qinghai Song, Physical Review Letters 135, 110601 
(2025). Commentary paper: 
https://phys.org/news/2025-10-strain-readout-quantum-technologies.html [12] 
Non-invasive bioinert room-temperature quantum sensor from silicon carbide 
qubits, Pei Li, Ji-Yang Zhou, Song Li, Péter Udvarhelyi, Jin-Shi Xu, 
Chuan-Feng Li, Bing Huang, Guang-Can Guo, and Adam Gali, Nature Materials, 
24, 1913 (2025). Commentary paper: 
https://phys.org/news/2025-11-quantum-sensor-based-silicon-carbide.html  
  PhD Preliminary DefenseIvan AbilioHUN-REN Wigner FK 
SZFIComputational strategies for scanning tunneling microscopy and 
spectroscopy of functional materialsTuesday, 9 December 2025, 13:00, ZoomThis 
dissertation details significant advances in computational strategies for 
simulating scanning tunneling microscopy (STM) and spectroscopy (STS). Main 
contributions are the implementation of the revised Chen methodology for STS 
simulations and the development of a tip-orbital decomposition technique for 
the same methodology, providing unprecedented insight into individual tip 
orbitals contribution to tunneling current and conductance. These were used 
to explain experimental STM images of CO/Cu adsorbates on a Cu(111) surface, 
to investigate the electronic properties of nitrogen-doped corrugated 
graphene, and to explore the tip-orbital contributions of different tips on 
B/N doped graphene. By improving theoretical methods, this research provides 
robust computational tools for understanding complex material systems at the 
atomic scale.Topic: Ivan Contini Abilio - PhD pre-defense @ WignerTime: Dec 
9, 2025 01:00 PM BudapestJoin Zoom 
Meetinghttps://wigner-hu.zoom.us/j/87113941425?pwd=gNbAfqb8a8IbM17e1hV3UsYSw8AhzV.1Meeting
 ID: 871 1394 1425Passcode: 630408Join 
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  Minden érdeklődőt szívesen látunk! - Everyone is welcome to 
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