المؤلفون: Kim, Min-Jae, Kovalev, Sergey, Udina, Mattia, Haenel, Rafael, Kim, Gideok, Puviani, Matteo, Cristiani, Georg, Ilyakov, Igor, de Oliveira, Thales V. A. G., Ponomaryov, Alexey, Deinert, Jan-Christoph, Logvenov, Gennady, Keimer, Bernhard, Manske, Dirk, Benfatto, Lara, Kaiser, Stefan

مصطلحات موضوعية: Condensed Matter - Superconductivity

الوصف: Ultrafast optical control of quantum systems is an emerging field of physics. In particular, the possibility of light-driven superconductivity with ultrashort laser pulses has attracted much of attention. To identify non-equilibrium superconductivity, it is necessary to measure fingerprints of superconductivity on ultrafast timescales. Recently non-linear THz third harmonic generation (THG) was shown to directly probe the collective degrees of freedoms of the superconducting condensate including particularly the Higgs mode. Here we extend this idea to light-driven non-equilibrium states in superconducting La2-xSrxCuO4 establishing a protocol to access the transient superconducting (SC) order-parameter fluctuations. We perform an optical pump-THz-THG drive experiment and use a two-dimensional spectroscopy approach to disentangle the driven third-harmonic response of optically excited quasiparticles and the pure condensate response. In this way, 2D spectroscopy separately probes both the ultrafast pair breaking dynamics and transient pairing amplitude of the condensate.
Comment: 28 pages, 12 figures

الوصول الحر: http://arxiv.org/abs/2303.03288Test

المؤلفون: Feng, Liwen, Cao, Jiayuan, Priessnitz, Tim, Dai, Yunyun, de Oliveira, Thales, Yuan, Jiayu, Kim, Min-Jae, Chen, Min, Ponomaryov, Alexey N., Ilyakov, Igor, Zhang, Haotian, Lv, Yongbo, Mazzotti, Valentina, Kim, Gideok, Christiani, Georg, Logvenov, Gennady, Wu, Dong, Huang, Yuan, Deinert, Jan-Christoph, Kovalev, Sergey, Dong, Tao, Wang, Nanlin, Kaiser, Stefan, Chu, Hao

مصطلحات موضوعية: Condensed Matter - Superconductivity

الوصف: 2H-NbSe2 is an archetypal system in which superconductivity and charge-density-wave (CDW) coexist and compete macroscopically with each other. In particular, this interplay also manifests in their dynamical fluctuations. As a result, the superconducting amplitude fluctuations (i.e. Higgs mode) is pushed below the quasiparticle continuum, allowing it to become a coherent excitation observable by Raman scattering. In the present study, we coherently drive the collective oscillations of the two orders and visualize their interplay in the driven states in the time domain. We find that both collective modes contribute to terahertz third harmonic generation (THG) and the THG signals interfere below Tc, leading to an anti-resonance of the integrated THG signal. The dynamical Ginzburg-Landau model suggests that around the anti-resonance a periodic energy transfer between the driven Higgs oscillations and the driven CDW oscillations is possible. In addition to 2H-NbSe2, we also studied an underdoped La2-xSrxCuO4 (x ~ 0.12) driven beyond the perturbative regime of THG. A similar interference between two sources of THG is observed below Tc. While there might be additional sources of THG in these experiments, our results illustrate the roles of coupled modes in the terahertz THG process and the tantalizing possibility of coherent control via such couplings.

الوصول الحر: http://arxiv.org/abs/2211.10947Test

المؤلفون: Yordanov, Petar, Priessnitz, Tim, Kim, Min-Jae, Cristiani, Georg, Logvenov, Gennady, Keimer, Bernhard, Kaiser, Stefan

مصطلحات موضوعية: Condensed Matter - Materials Science, Physics - Optics

الوصف: Terahertz (THz) radiation is a powerful tool with widespread applications ranging from imaging, sensing, and broadband communications to spectroscopy and nonlinear control of materials. Future progress in THz technology depends on the development of efficient, structurally simple THz emitters that can be implemented in advanced miniaturized devices. Here we show how the natural electronic anisotropy of layered conducting transition metal oxides enables the generation of intense terahertz radiation via the transverse thermoelectric effect. In thin films grown on offcut substrates, femtosecond laser pulses generate ultrafast out-of-plane temperature gradients, which in turn launch in-plane thermoelectric currents, thus allowing efficient emission of the resulting THz field out of the film structure. We demonstrate this scheme in experiments on thin films of the layered metals PdCoO2 and La1.84Sr0.16CuO4, and present model calculations that elucidate the influence of the material parameters on the intensity and spectral characteristics of the emitted THz field. Due to its simplicity, the method opens up a promising avenue for the development of highly versatile THz sources and integrable emitter elements.
Comment: 27 pages, 11 figures

الوصول الحر: http://arxiv.org/abs/2208.01480Test

المؤلفون: Bluschke, Martin, Basak, Rourav, Barbour, Andi, Warner, Ashley N, Fürsich, Katrin, Wilkins, Stuart, Roy, Sujoy, Lee, James, Christiani, Georg, Logvenov, Gennady, Minola, Matteo, Keimer, Bernhard, Mazzoli, Claudio, Benckiser, Eva, Frano, Alex

المصدر: Science Advances. 8(29)

مصطلحات موضوعية: Inorganic Chemistry, Quantum Physics, Chemical Sciences, Physical Sciences

الوصف: The detection and manipulation of antiferromagnetic domains and topological antiferromagnetic textures are of central interest to solid-state physics. A fundamental step is identifying tools to probe the mesoscopic texture of an antiferromagnetic order parameter. In this work, we demonstrate that Bragg coherent diffractive imaging can be extended to study the mesoscopic texture of an antiferromagnetic order parameter using resonant magnetic x-ray scattering. We study the onset of the antiferromagnet transition in PrNiO3, focusing on a temperature regime in which the antiferromagnetic domains are dilute in the beam spot and the coherent diffraction pattern modulating the antiferromagnetic peak is greatly simplified. We demonstrate that it is possible to extract the arrangements and sizes of these domains from single diffraction patterns and show that the approach could be extended to a time-structured light source to study the motion of dilute domains or the motion of topological defects in an antiferromagnetic spin texture.

وصف الملف: application/pdf

الوصول الحر: https://escholarship.org/uc/item/70w021ccTest

المؤلفون: Chu, Hao, Kovalev, Sergey, Wang, Zi Xiao, Schwarz, Lukas, Dong, Tao, Feng, Liwen, Haenel, Rafael, Kim, Min-Jae, Shabestari, Parmida, Phuong, Hoang Le, Honasoge, Kedar, Dawson, Robert David, Putzky, Daniel, Kim, Gideok, Puviani, Matteo, Chen, Min, Awari, Nilesh, Ponomaryov, Alexey N., Ilyakov, Igor, Bluschke, Martin, Boschini, Fabio, Zonno, Marta, Zhdanovich, Sergey, Na, Mengxing, Christiani, Georg, Logvenov, Gennady, Jones, David J., Damascelli, Andrea, Minola, Matteo, Keimer, Bernhard, Manske, Dirk, Wang, Nanlin, Deinert, Jan-Christoph, Kaiser, Stefan

المصدر: Nature Communications volume 14, Article number: 1343 (2023)

مصطلحات موضوعية: Condensed Matter - Superconductivity, Condensed Matter - Strongly Correlated Electrons

الوصف: Despite decades of search for the pairing boson in cuprate high-Tc superconductors, its identity still remains debated to date. For this reason, spectroscopic signatures of electron-boson interactions in cuprates have always been a center of attention. For example, the kinks in the quasiparticle dispersion observed by angle-resolved photoemission spectroscopy (ARPES) studies have motivated a decade-long investigation of electron-phonon as well as electron-paramagnon interactions in cuprates. On the other hand, the overlap between the charge-order correlations and the pseudogap in the cuprate phase diagram has also generated discussions about the potential link between them. In the present study, we provide a fresh perspective on these intertwined interactions using the novel approach of Higgs spectroscopy, i.e. an investigation of the amplitude oscillations of the superconducting order parameter driven by a terahertz radiation. Uniquely for cuprates, we observe a Fano interference of its dynamically driven Higgs mode with another collective mode, which we reveal to be charge density wave fluctuations from an extensive doping- and magnetic field-dependent study. This finding is further corroborated by a mean field model in which we describe the microscopic mechanism underlying the interaction between the two orders. Our work demonstrates Higgs spectroscopy as a novel and powerful technique for investigating intertwined orders and microscopic processes in unconventional superconductors.

الوصول الحر: http://arxiv.org/abs/2109.09971Test

المؤلفون: Bonmassar, Nicolas, Christiani, Georg, Brucker, Maximilian, Logvenov, Gennady, Suyolcu, Y. Eren, van Aken, Peter A.

المصدر: Advanced Functional Materials ; ISSN 1616-301X 1616-3028

الوصف: The pursuit of breakthroughs in thin film technology drives the exploration of novel growth strategies for quantum materials that surpass conventional limitations. Departing from the prevailing unidirectional growth approach, the methodology allows for atomic precision in both the in‐plane and out‐of‐plane directions. To demonstrate the capabilities of this transformative technique, a bi‐directionally grown superlattice comprised of alternating LaMnO 3 and SrMnO 3 layers is engineered, enabling the emergence of interfacial ferromagnetism. By adopting this superlattice as a model system, the vast potential of the approach is highlighted through comprehensive analysis and characterization. Furthermore, the application of the method is extended to the growth of superconducting La 1.84 Sr 0.16 CuO 4 thin films on various offcut substrates. Remarkably, these substrates induce an anisotropic critical current originating from two distinct mechanisms.

الإتاحة: https://doi.org/10.1002/adfm.202314698Test

المؤلفون: Yang, Chao, Pons, Rebecca, Sigle, Wilfried, Wang, Hongguang, Benckiser, Eva, Logvenov, Gennady, Keimer, Bernhard, van Aken, Peter A.

المساهمون: the European Union's Horizon 2020 research and innovation programme

المصدر: Nature Communications ; volume 15, issue 1 ; ISSN 2041-1723

مصطلحات موضوعية: General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary

الوصف: The polarity of a surface can affect the electronic and structural properties of oxide thin films through electrostatic effects. Understanding the mechanism behind these effects requires knowledge of the atomic structure and electrostatic characteristics at the surface. In this study, we use annular bright-field imaging to investigate the surface structure of a Pr 0.8 Sr 0.2 NiO 2+ x (0 < x < 1) film. We observe a polar distortion coupled with octahedral rotations in a fully oxidized Pr 0.8 Sr 0.2 NiO 3 sample, and a stronger polar distortion in a partially reduced sample. Its spatial depth extent is about three unit cells from the surface. Additionally, we use four-dimensional scanning transmission electron microscopy (4D-STEM) to directly image the local atomic electric field surrounding Ni atoms near the surface and discover distinct valence variations of Ni atoms, which are confirmed by atomic-resolution electron energy-loss spectroscopy (EELS). Our results suggest that the strong surface reconstruction in the reduced sample is closely related to the formation of oxygen vacancies from topochemical reduction. These findings provide insights into the understanding and evolution of surface polarity at the atomic level.

الإتاحة: https://doi.org/10.1038/s41467-023-44616-xTest
https://www.nature.com/articles/s41467-023-44616-x.pdfTest
https://www.nature.com/articles/s41467-023-44616-xTest

المؤلفون: Bonmassar, Nicolas, Christiani, Georg, Logvenov, Gennady, Suyolcu, Y. Eren, van Aken, Peter A.

المساهمون: Max-Planck-Gesellschaft

المصدر: Nano Letters ; volume 24, issue 18, page 5556-5561 ; ISSN 1530-6984 1530-6992

الإتاحة: https://doi.org/10.1021/acs.nanolett.4c00832Test

المؤلفون: Wu, Ze-Bin, Putzky, Daniel, Kundu, Asish K., Li, Hui, Yang, Shize, Du, Zengyi, Joo, Sang Hyun, Lee, Jinho, Zhu, Yimei, Logvenov, Gennady, Keimer, Bernhard, Fujita, Kazuhiro, Valla, Tonica, Bozovic, Ivan, Drozdov, Ilya K.

مصطلحات موضوعية: Condensed Matter - Superconductivity, Condensed Matter - Materials Science

الوصف: Much of what is known about high-temperature cuprate superconductors stems from studies based on two surface analytical tools, angle-resolved photoemission spectroscopy (ARPES) and spectroscopic imaging scanning tunneling microscopy (SI-STM). A question of general interest is whether and when the surface properties probed by ARPES and SI-STM are representative of the intrinsic properties of bulk materials. We find this question is prominent in thin films of a rarely studied cuprate DBCO. We synthesize DBCO films by oxide molecular beam epitaxy and study them by in situ ARPES and SI-STM. Both ARPES and SI-STM show that the surface DBCO layer is different from the bulk of the film. It is heavily underdoped, while the doping level in the bulk is close to optimal doping evidenced by bulk-sensitive mutual inductance measurements. ARPES shows the typical electronic structure of a heavily underdoped CuO2 plane and two sets of one-dimensional bands originating from the CuO chains with one of them gapped. SI-STM reveals two different energy scales in the local density of states, with one corresponding to the superconductivity and the other one to the pseudogap. While the pseudogap shows large variations over the length scale of a few nanometers, the superconducting gap is very homogeneous. This indicates that the pseudogap and superconductivity are of different origins.

الوصول الحر: http://arxiv.org/abs/2101.10303Test

المؤلفون: Betto, Davide, Bluschke, Martin, Putzky, Daniel, Schierle, Enrico, Amorese, Andrea, Fürsich, Katrin, Blanco-Canosa, Santiago, Christiani, Georg, Logvenov, Gennady, Keimer, Bernhard, Minola, Matteo

مصطلحات موضوعية: Condensed Matter - Superconductivity

الوصف: We used resonant elastic x-ray scattering at the Cu $L_3$ and Dy $M_5$ edges to investigate charge order in thin films of underdoped DyBa$_2$Cu$_3$O$_{6+x}$ (DyBCO) epitaxially grown on NdGaO$_3$ (110) substrates. The films show an orthorhombic crystal structure with short-range ortho-II oxygen order in the charge-reservoir layers. At the Dy $M_5$ edge we observe diffraction peaks with the same planar wavevectors as those of the two-dimensional charge density wave in the CuO$_2$ planes and of the ortho-II oxygen order, indicating the formation of induced ordered states on the rare-earth sublattice. The intensity of the resonant diffraction peaks exhibits a non-monotonic dependence on an external magnetic field. Model calculations on the modulation of the crystalline electric field at the Dy sites by charge and oxygen order capture the salient features of the magnetic field, temperature, and photon energy dependence of the scattering intensity.
Comment: 9 pages, 10 figures

الوصول الحر: http://arxiv.org/abs/2009.03574Test