Magnetic-Field Tuning of the Spin Dynamics in the Quasi-2D Van der Waals Antiferromagnet CuCrP2S6 Joyal John Abraham, Yaqian Guo, Yuliia Shemerliuk, Sebastian Selter, Saicharan Aswartham, Kranthi Kumar Bestha, Laura T. Corredor, Anja U. B. Wolter, Olga Kataeva, Luka Rogić, Noah Somun, Damjan Pelc, Oleg Janson, Jeroen van den Brink, Bernd Büchner, Vladislav Kataev, Alexey Alfonsov Advanced Functional Materials, 2026 The use of antiferromagnets in magnetoelectronic devices as counterparts of ferromagnets is a new, rapidly developing trend in spintronics that leverages antiferromagnetic (AFM) magnons for transmitting of spin currents. Van der Waals (vdW) antiferromagnets are particularly attractive in this respect as they possess tunable magnetic properties and can be easily integrated into spintronic devices. In this work, electron spin resonance (ESR) spectroscopy is used to assess the potential of the vdW AFM compound CuCrP2S6 for magnonic applications by exploring the magnetic field (H) dependence of the spectrum of magnon excitations below its AFM ordering temperature TN ≈ 30 K and the correlated spin dynamics above TN. ESR reveals prominent ferromagnetic (FM) spin correlations that persist far above TN suggesting an intrinsically 2D character of the spin dynamics in CuCrP2S6. Most interestingly, at T < TN, CuCrP2S6 features two non‐degenerate, i.e., distinct in energy AFM magnon modes at H = 0 which can be tuned to the FM type of collective spin excitations with increasing H. These remarkable properties are favorable for the induction and control of unidirectional spin current in CuCrP2S6 and suggest it as a new functional material for magnetoelectronics.
Electronic spin susceptibility in metallic strontium titanate A. Najev, N. Somun, M. Spaić, I. Khayr, M. Greven, A. Klein, M. N. Gastiasoro, D. Pelc Npj Quantum Materials, 2025 Metallic strontium titanate (SrTiO 3 ) is known to have both normal-state and superconducting properties that strongly vary over a wide range of charge carrier densities, but the complex interplay between lattice and electronic degrees of freedom has hindered the development of a clear qualitative description of the observed behavior. A major challenge is to understand how the charge carriers themselves evolve with doping and temperature, with possible polaronic effects and evidence of an effective mass that strongly increases with temperature. Here we use 47,49 Ti nuclear magnetic resonance (NMR) to perform a comprehensive study of the electronic spin susceptibility in the metallic state of strontium titanate across the doping-temperature phase diagram. We find a temperature-dependent Knight shift that can be quantitatively understood within a nondegenerate Fermi gas model that fully takes into account the complex band structure of SrTiO 3 . Our data are consistent with a temperature-independent effective mass, and we show that the behavior of the spin susceptibility is universal in a wide range of temperatures and carrier concentrations. These results provide a microscopic foundation for the understanding of the properties of the unconventional low-density metallic state in strontium titanate and related materials.
Cryogenic continuous-wave optical spectrometer for sub-THz frequencies L. Rogić, N. Somun, S. Griffitt, A. Najev, M. Spaić, S. Hameed, Y. Shemerliuk, S. Aswartham, M. Orlita, A. Alfonsov, D. Pelc Review of Scientific Instruments, 2025 We present the design of a continuous-wave, highly sensitive optical spectrometer for millimeter-wave frequencies between 50 and 1000 GHz, with optimal performance at cryogenic temperatures. The spectrometer uses photomixing of near-infrared light to generate radiation over a wide frequency range, and the optical power absorbed by the sample is determined directly by measuring the sample temperature. This enables a dynamic range of up to 106 for the absorption coefficient below liquid-helium temperatures, making it suitable for measurements on highly reflective samples. The instrument can also be used in combination with high magnetic fields. In order to validate its performance, we measure the ferromagnetic resonance in the Mott insulator YTiO3, the electron spin resonance in a standard free-radical reference compound, and the antiferromagnetic resonance in a van der Waals magnetic material.
Cu NMR study of lightly doped la 2- xSr xCuO4 Marija Vučković, Ana Najev, Biqiong Yu, Takao Sasagawa, Nina Bielinski, Neven Barišić, Martin Greven, Damjan Pelc, Miroslav Požek Physical Review B, 2025 We present a single-crystal Cu nuclear magnetic resonance (NMR) study of the cuprate superconductor ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}$ with hole-doping levels between $x=2$ and 8%. Measurements with short spin echo times enable us to systematically study the local properties of the electronic spin system in the region of the phase diagram where the material evolves from the insulating antiferromagnetic parent phase to the superconducting state. We find evidence for qualitative changes as the Sr concentration increases through $x=5$% in both NMR spectra and relaxation times, which we interpret as signatures of a low-temperature transition from a state with disconnected metallic islands to a granular metal with tunneling between the grains. These results provide microscopic insight into the physics of a doped charge-transfer insulator in the presence of quenched substitutional disorder, indicate that a connectivity transition occurs, and demonstrate that complex nanoscale electronic phase separation is ubiquitous in LSCO around the doping level where superconductivity first appears in the phase diagram.
Diffuse scattering from correlated electron systems Raymond Osborn, Damjan Pelc, Matthew J. Krogstad, Stephan Rosenkranz, Martin Greven Science Advances, 2025 The role of inhomegeneity in determining the properties of correlated electron systems is poorly understood because of the dearth of structural probes of disorder at the nanoscale. Advances in both neutron and x-ray scattering instrumentation now allow comprehensive measurements of diffuse scattering in single crystals over large volumes of reciprocal space, enabling structural correlations to be characterized over a range of length scales from 5 to 200 angstroms or more. When combined with new analysis tools, such as three-dimensional difference pair-distribution functions, these advanced capabilities have produced fresh insights into the interplay of structural fluctuations and electronic properties in a broad range of correlated electron materials. This review describes recent investigations that have demonstrated the importance of understanding structural inhomogeneity pertaining to phenomena as diverse as superconductivity, charge density wave modulations, metal-insulator transitions, and multipolar interactions.
Nanoscale structural correlations in a model cuprate superconductor Zachary W. Anderson, Marin Spaić, Nikolaos Biniskos, Liam Thompson, Biqiong Yu, Jack Zwettler, Yaohua Liu, Feng Ye, Garrett E. Granroth, Matthew Krogstad, Raymond Osborn, Damjan Pelc, Martin Greven Physical Review B, 2024 Understanding the extent and role of inhomogeneity is a pivotal challenge in the physics of cuprate superconductors. While it is known that structural and electronic inhomogeneity is prevalent in the cuprates, it has proven difficult to disentangle compound-specific features from universally relevant effects. Here we combine advanced neutron and x-ray diffuse scattering with numerical modeling to obtain insight into bulk structural correlations in HgBa$_2$CuO$_{4+\\delta}$. This cuprate exhibits a high optimal transition temperature of nearly 100 K, pristine charge-transport behavior, and a simple average crystal structure without long-range structural instabilities, and is therefore uniquely suited for investigations of intrinsic inhomogeneity. We uncover diffuse reciprocal-space patterns that correspond to prominent nanoscale correlations of atomic displacements perpendicular to the CuO$_2$ planes. The real-space nature of the correlations is revealed through three-dimensional pair distribution function analysis and complementary numerical refinement. We find that relative displacements of ionic and CuO$_2$ layers play a crucial role, and that the structural inhomogeneity is not directly caused by the presence of conventional point defects. The observed correlations are therefore intrinsic to HgBa$_2$CuO$_{4+\\delta}$, and thus likely important for the physics of cuprates more broadly. It is possible that the structural correlations are closely related to the unusual superconducting correlations and Mott-localization in these complex oxides. As advances in scattering techniques yield increasingly comprehensive data, the experimental and analysis tools developed here for large volumes of diffuse scattering data can be expected to aid future investigations of a wide range of materials.
Multiferroicity in plastically deformed SrTiO3 Xi Wang, Anirban Kundu, Bochao Xu, Sajna Hameed, Nadav Rothem, Shai Rabkin, Luka Rogić, Liam Thompson, Alexander McLeod, Martin Greven, Damjan Pelc, Ilya Sochnikov, Beena Kalisky, Avraham Klein Nature Communications, 2024 Quantum materials have a fascinating tendency to manifest novel and unexpected electronic states upon proper manipulation. Ideally, such manipulation should induce strong and irreversible changes and lead to new relevant length scales. Plastic deformation introduces large numbers of dislocations into a material, which can organize into extended structures and give rise to qualitatively new physics as a result of the huge localized strains. However, this approach is largely unexplored in the context of quantum materials, which are traditionally grown to be as pristine and clean as possible. Here we show that plastic deformation induces robust magnetism in the quantum paraelectric SrTiO3, a property that is completely absent in the pristine material. We combine scanning magnetic measurements and near-field optical microscopy to find that the magnetic order is localized along dislocation walls and coexists with ferroelectric order along the walls. The magnetic signals can be switched on and off via external stress and altered by external electric fields, which demonstrates that plastically deformed SrTiO3 is a quantum multiferroic. These results establish plastic deformation as a versatile knob for the manipulation of the electronic properties of quantum materials. Plastic deformation induces robust magnetism in SrTiO3, which is completely absent in pristine samples. This magnetism coexists with ferroelectric order, showcasing plastic deformation as a powerful tool for manipulating quantum material properties.
Structural properties of plastically deformed SrTiO3 and KTaO3 Issam Khayr, Sajna Hameed, Jakov Budić, Xing He, Richard Spieker, Ana Najev, Zinan Zhao, Li Yue, Matthew Krogstad, Feng Ye, Yaohua Liu, Raymond Osborn, Stephan Rosenkranz, Yuan Li, Damjan Pelc, Martin Greven Physical Review Materials, 2024 Dislocation engineering has the potential to open new avenues toward the exploration and modification of the properties of quantum materials. Strontium titanate ($\mathrm{SrTi}{\mathrm{O}}_{3}$, STO) and potassium tantalate ($\mathrm{KTa}{\mathrm{O}}_{3}$, KTO) are incipient ferroelectrics that show metallization and superconductivity at extremely low charge-carrier concentrations and have been the subject of resurgent interest. These materials also exhibit remarkable ambient-temperature ductility, and thus represent exceptional platforms for studies of the effects of deformation-induced dislocation structures on electronic properties. Recent work on plastically deformed STO revealed an enhancement of the superconducting transition temperature and the emergence of local ferroelectricity and magnetism near self-organized dislocation walls. Here we present a comprehensive structural analysis of plastically deformed STO and KTO, employing specially designed strain cells, diffuse neutron and x-ray scattering, Raman scattering, and nuclear magnetic resonance (NMR). Diffuse scattering and NMR provide insight into the dislocation configurations and densities and their dependence on strain. As in the prior work on STO, Raman scattering reveals evidence for local ferroelectric order near dislocation walls in plastically deformed KTO. Our findings provide valuable information about the self-organized defect structures in both materials, and they position KTO as a second model system in which to explore the associated emergent physics.
Magnetic resonance study of rare-earth titanates A. Najev, S. Hameed, A. Alfonsov, J. Joe, V. Kataev, M. Greven, M. Požek, D. Pelc Physical Review B, 2024 We present a nuclear magnetic resonance (NMR) and electron spin resonance (ESR) study of rare-earth titanates derived from the spin-1/2 Mott insulator YTiO$_3$. Measurements of single-crystalline samples of (Y,Ca,La)TiO$_3$ in a wide range of isovalent substitution (La) and hole doping (Ca) reveal several unusual features in the paramagnetic state of these materials. $^{89}$Y NMR demonstrates a clear discrepancy between the static and dynamic local magnetic susceptibilities, with deviations from Curie-Weiss behavior far above the Curie temperature $T_C$. No significant changes are observed close to $T_C$, but a suppression of fluctuations is detected in the NMR spin-lattice relaxation time at temperatures of about $3\\times T_C$. Additionally, the nuclear spin-spin relaxation rate shows an unusual peak in dependence on temperature for all samples. ESR of the unpaired Ti electron shows broad resonance lines at all temperatures and substitution/doping levels, which we find to be caused by short electronic spin-lattice relaxation times. We model the relaxation as an Orbach process that involves a low-lying electronic excited state, which enables the determination of the excited-state gap from the temperature dependence of the ESR linewidths. We ascribe the small gap to Jahn-Teller splitting of the two lower Ti $t_{2g}$ orbitals. The value of the gap closely follows $T_C$ and is consistent with the temperatures at which deviations from Curie-Weiss fluctuations are observed in NMR. These results provide insight into the interplay between orbital and spin degrees of freedom in rare-earth titanates and indicate that full orbital degeneracy lifting is associated with ferromagnetic order.
Unconventional short-range structural fluctuations in cuprate superconductors D. Pelc, R. J. Spieker, Z. W. Anderson, M. J. Krogstad, N. Biniskos, N. G. Bielinski, B. Yu, T. Sasagawa, L. Chauviere, P. Dosanjh, R. Liang, D. A. Bonn, A. Damascelli, S. Chi, Y. Liu, R. Osborn, M. Greven Scientific Reports, 2022
Pervasive symmetry-lowering nanoscale structural fluctuations in the cuprate La2− 𝑥 Sr𝑥 Cu O4 RJ Spieker, M Spaić, I Khayr, X He, D Zhai, ZW Anderson, N Bielinski, ... Physical Review. B 113 (1) , 2026 2026
Magnetic‐Field Tuning of the Spin Dynamics in the Quasi‐2D Van der Waals Antiferromagnet CuCrP 2 S 6 JJ Abraham, Y Guo, Y Shemerliuk, S Selter, S Aswartham, KK Bestha, ... Advanced Functional Materials 36 (5), e11057 , 2026 2026 Citations: 1
Pervasive symmetry-lowering nanoscale structural fluctuations in the cuprate RJ Spieker, M Spaić, I Khayr, X He, D Zhai, ZW Anderson, N Bielinski, ... Physical Review B 113 (1), 014101 , 2026 2026
Evidence for rare-region physics in the structural and electronic degrees of freedom of the nickelate La Sr NiO RJ Spieker, B Krohnke, D Zhai, AL Benet, M Spaić, X He, CY Tan, ... arXiv preprint arXiv:2512.23655 , 2025 2025
Uniaxial strain tuning of polar lattice vibrations in KTaO and SrTiO I Khayr, N Somun, S Hameed, Z Van Fossan, X He, R Spieker, S Chi, ... arXiv preprint arXiv:2511.10623 , 2025 2025
Cryogenic continuous-wave optical spectrometer for sub-THz frequencies L Rogić, N Somun, S Griffitt, A Najev, M Spaić, S Hameed, Y Shemerliuk, ... Review of scientific instruments 96 (8) , 2025 2025
Cu NMR study of lightly doped La2-xSrxCuO4 M Vuckovic, A Najev, B Yu, T Sasagawa, N Bielinski, N Barisic, M Greven, ... PHYSICAL REVIEW B 111 (18) , 2025 2025 Citations: 1
Cu NMR study of lightly doped M Vučković, A Najev, B Yu, T Sasagawa, N Bielinski, N Barišić, M Greven, ... Physical Review B 111 (18), 184509 , 2025 2025 Citations: 3
Electronic and Structural Changes in Plastically Deformed Tellurides S Anderson, X He, I Khayr, J Budic, B Gudac, N Somun, S Sarker, ... SMT 2025 , 2025 2025
Ionic-liquid-gating study of the incipient ferroelectrics SrTiO 3 and KTaO 3 CY Tan, I Khayr, D Pelc, M Greven SMT 2025 , 2025 2025
Strain tuning of Soft Phonons in Incipient Ferroelectrics I Khayr, X He, N Somun, RJ Spieker, S Anderson, Z Van Fossan, ... SMT 2025 , 2025 2025
Strain-tuning of transport properties in the half-Heusler topological semimetal GdPtBi S Sharma, JA Payne, D Pelc, M Greven SMT 2025 , 2025 2025
Electronic and structural properties of HgBa 2 Ca 2 Cu 3 O 8+δ , the highest-T c superconductor at ambient pressure SS Gorregattu, CY Tan, W Hong, D Pelc, Y Li, M Greven SMT 2025 , 2025 2025
Diffuse scattering from correlated electron systems R Osborn, D Pelc, MJ Krogstad, S Rosenkranz, M Greven Science Advances 11 (7), eadt7770 , 2025 2025 Citations: 15
Electronic spin susceptibility in metallic strontium titanate A Najev, N Somun, M Spaić, I Khayr, M Greven, A Klein, MN Gastiasoro, ... npj quantum materials 10 (1), 4 , 2025 2025 Citations: 2
Nanoscale structural correlations in a model cuprate superconductor ZW Anderson, M Spaić, N Biniskos, L Thompson, B Yu, J Zwettler, Y Liu, ... Physical Review B 110 (21), 214519 , 2024 2024 Citations: 6
Continuous-wave cryogenic optical absorption spectrometer for sub-THz frequencies L Rogić, N Somun, S Griffitt, A Najev, M Spaić, S Hameed, Y Shemerliuk, ... arXiv preprint arXiv:2411.15910 , 2024 2024
Multiferroicity in plastically deformed SrTiO 3 X Wang, A Kundu, B Xu, S Hameed, N Rothem, S Rabkin, L Rogić, ... Nature communications 15 (1), 7442 , 2024 2024 Citations: 20
Structural properties of plastically deformed SrTiO3 and KTaO3 I Khayr, S Hameed, J Budić, X He, R Spieker, A Najev, Z Zhao, L Yue, ... arXiv preprint arXiv:2405.13249 , 2024 2024 Citations: 11
Magnetic resonance study of rare-earth titanates A Najev, S Hameed, A Alfonsov, J Joe, V Kataev, M Greven, M Požek, ... Physical Review B 109 (17), 174406 , 2024 2024 Citations: 4
MOST CITED SCHOLAR PUBLICATIONS
Enhanced superconductivity and ferroelectric quantum criticality in plastically deformed strontium titanate S Hameed, D Pelc, ZW Anderson, A Klein, RJ Spieker, L Yue, B Das, ... Nature materials 21 (1), 54-61 , 2022 2022 Citations: 126
Emergence of superconductivity in the cuprates via a universal percolation process D Pelc, M Vučković, MS Grbić, M Požek, G Yu, T Sasagawa, M Greven, ... Nature communications 9 (1), 4327 , 2018 2018 Citations: 108
Unusual behavior of cuprates explained by heterogeneous charge localization D Pelc, P Popčević, M Požek, M Greven, N Barišić Science advances 5 (1), eaau4538 , 2019 2019 Citations: 94
Universal superconducting precursor in three classes of unconventional superconductors D Pelc, Z Anderson, B Yu, C Leighton, M Greven Nature communications 10 (1), 2729 , 2019 2019 Citations: 60
Resistivity phase diagram of cuprates revisited D Pelc, MJ Veit, CJ Dorow, Y Ge, N Barišić, M Greven Physical Review B 102 (7), 075114 , 2020 2020 Citations: 43
Percolative nature of the direct-current paraconductivity in cuprate superconductors P Popčević, D Pelc, Y Tang, K Velebit, Z Anderson, V Nagarajan, G Yu, ... npj quantum materials 3 (1), 42 , 2018 2018 Citations: 43
Role of microscopic phase separation in gelation of aqueous gelatin solutions D Pelc, S Marion, M Požek, M Basletić Soft matter 10 (2), 348-356 , 2014 2014 Citations: 38
Universal precursor of superconductivity in the cuprates G Yu, DD Xia, D Pelc, RH He, NH Kaneko, T Sasagawa, Y Li, X Zhao, ... Physical Review B 99 (21), 214502 , 2019 2019 Citations: 32
Uniaxial strain control of bulk ferromagnetism in rare-earth titanates A Najev, S Hameed, D Gautreau, Z Wang, J Joe, M Požek, T Birol, ... Physical review letters 128 (16), 167201 , 2022 2022 Citations: 31
Unconventional charge order in a co-doped high- T c superconductor D Pelc, M Vučković, HJ Grafe, SH Baek, M Požek Nature communications 7 (1), 12775 , 2016 2016 Citations: 29
Determination of the hyperfine magnetic field in magnetic carbon-based materials: DFT calculations and NMR experiments JCC Freitas, WL Scopel, WS Paz, LV Bernardes, FE Cunha-Filho, ... Scientific reports 5 (1), 14761 , 2015 2015 Citations: 24
Local inversion-symmetry breaking in a bismuthate high- T c superconductor S Griffitt, M Spaić, J Joe, ZW Anderson, D Zhai, MJ Krogstad, R Osborn, ... Nature communications 14 (1), 845 , 2023 2023 Citations: 22
Unconventional short-range structural fluctuations in cuprate superconductors D Pelc, RJ Spieker, ZW Anderson, MJ Krogstad, N Biniskos, NG Bielinski, ... Scientific reports 12 (1), 20483 , 2022 2022 Citations: 22
Multiferroicity in plastically deformed SrTiO 3 X Wang, A Kundu, B Xu, S Hameed, N Rothem, S Rabkin, L Rogić, ... Nature communications 15 (1), 7442 , 2024 2024 Citations: 20
Cu nuclear magnetic resonance study of charge and spin stripe order in D Pelc, HJ Grafe, GD Gu, M Požek Physical Review B 95 (5), 054508 , 2017 2017 Citations: 19
Knight shift study of the interplay between superconductivity and pseudogap in T Cvitanić, D Pelc, M Požek, E Amit, A Keren Physical Review B 90 (5), 054508 , 2014 2014 Citations: 17
Diffuse scattering from correlated electron systems R Osborn, D Pelc, MJ Krogstad, S Rosenkranz, M Greven Science Advances 11 (7), eadt7770 , 2025 2025 Citations: 15
Mechanism of metallization and superconductivity suppression in YBa 2 (Cu 0.97 Zn 0.03 ) 3 O 6.92 revealed by 67 Zn NQR D Pelc, M Požek, V Despoja, DK Sunko New journal of physics 17 (8), 083033 , 2015 2015 Citations: 15
Four-contact impedance spectroscopy of conductive liquid samples D Pelc, S Marion, M Basletić Review of scientific instruments 82 (7) , 2011 2011 Citations: 15
Effective numbers of charge carriers in doped graphene: Generalized Fermi liquid approach I Kupčić, G Nikšić, Z Rukelj, D Pelc Physical Review B 94 (7), 075434 , 2016 2016 Citations: 12