1
|
Wang S, Han Y, Sun S, Wang S, An C, Chen C, Zhang L, Zhou Y, Zhou J, Yang Z. Pressure Induced Nonmonotonic Evolution of Superconductivity in 6R-TaS_{2} with a Natural Bulk Van der Waals Heterostructure. PHYSICAL REVIEW LETTERS 2024; 133:056001. [PMID: 39159112 DOI: 10.1103/physrevlett.133.056001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 06/01/2024] [Accepted: 06/26/2024] [Indexed: 08/21/2024]
Abstract
The natural bulk Van der Waals heterostructure compound 6R-TaS_{2} consists of alternate stacking 1T- and 1H-TaS_{2} monolayers, creating a unique system that incorporates charge-density-wave (CDW) order and superconductivity (SC) in distinct monolayers. Here, after confirming that the 2D nature of the lattice is preserved up to 8 GPa in 6R-TaS_{2}, we documented an unusual evolution of CDW and SC by conducting high-pressure electronic transport measurements. Upon compression, we observe a gradual suppression of CDW within the 1T layers, while the SC exhibits a dome-shaped behavior that terminates at a critical pressure P_{c} around 2.9 GPa. By taking account of the fact that the substantial suppression of SC is concomitant with the complete collapse of CDW order at P_{c}, we argue that the 6R-TaS_{2} behaves like a stack of Josephson junctions and thus the suppressed superconductivity can be attributed to the weakening of Josephson coupling associated with the presence of CDW fluctuations in the 1T layers. Furthermore, the SC reversely enhances above P_{c}, implying the development of emergent superconductivity in the 1T layers after the melting of T-layer CDW orders. These results show that the 6R-TaS_{2} not only provides a promising platform to explore emergent phenomena but also serves as a model system to study the complex interactions between competing electronic states.
Collapse
Affiliation(s)
| | | | - Sutao Sun
- National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
| | | | | | | | | | | | - Jian Zhou
- National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
| | - Zhaorong Yang
- Anhui Key Laboratory of Low-energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- Science Island Branch of Graduate School, University of Science and Technology of China, Hefei 230026, China
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| |
Collapse
|
2
|
Morgan HWT, Yamamoto T, Nishikubo T, Ohmi T, Koike T, Sakai Y, Azuma M, Ishii H, Kobayashi G, McGrady JE. Sequential Pressure-Induced B1- B2 Transitions in the Anion-Ordered Oxyhydride Ba 2YHO 3. Inorg Chem 2022; 61:7043-7050. [PMID: 35451819 PMCID: PMC9092455 DOI: 10.1021/acs.inorgchem.2c00465] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
![]()
We present a detailed
experimental and computational investigation
of the influence of pressure on the mixed-anion oxyhydride phase Ba2YHO3, which has recently been shown to support
hydride conductivity. The unique feature of this layered perovskite
is that the oxide and hydride anions are segregated into distinct
regions of the unit cell, in contrast to the disordered arrangement
in closely related Ba2ScHO3. Density functional
theory (DFT) calculations reveal that the application of pressure
drives two sequential B1–B2 transitions in the interlayer regions from rock salt to CsCl-type
ordering, one in the hydride-rich layer at approximately 10 GPa and
another in the oxide-rich layer at 35–40 GPa. To verify the
theoretical predictions, we experimentally observe the structural
transition at 10 GPa using high-pressure X-ray diffraction (XRD),
but the details of the structure cannot be solved due to peak broadening
of the XRD patterns. We use DFT to explore the structural impact of
pressure on the atomic scale and show how the pressure-dependent properties
can be understood in terms of simple electrostatic engineering. We investigate a sequence of pressure-induced
phase transitions
in Ba2YHO3, a perovskite oxyhydride with a unique
layered anion ordering. Density functional theory and X-ray diffraction
together provide a detailed and informative picture of the changes
to the crystal structure across the pressure range. This work provides
new insights into nonuniform structural flexibility in 2D materials,
which can aid targeted materials design in other chemical systems.
Collapse
Affiliation(s)
- Harry W T Morgan
- Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, United States.,Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| | - Takafumi Yamamoto
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Takumi Nishikubo
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan.,Kanagawa Institute of Industrial Science and Technology, Ebina 243-0435, Japan
| | - Takuya Ohmi
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Takehiro Koike
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Yuki Sakai
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan.,Kanagawa Institute of Industrial Science and Technology, Ebina 243-0435, Japan
| | - Masaki Azuma
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan.,Kanagawa Institute of Industrial Science and Technology, Ebina 243-0435, Japan
| | - Hirofumi Ishii
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Genki Kobayashi
- Department of Materials Molecular Science, Institute for Molecular Science, 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan.,SOKENDAI (The Graduate University for Advanced Studies), 38 Nishigonaka, Myodaiji, Okazaki, Aichi 444-8585, Japan
| | - John E McGrady
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom
| |
Collapse
|
3
|
Deng H, Zhang J, Jeong MY, Wang D, Hu Q, Zhang S, Sereika R, Nakagawa T, Chen B, Yin X, Xiao H, Hong X, Ren J, Han MJ, Chang J, Weng H, Ding Y, Lin HQ, Mao HK. Metallization of Quantum Material GaTa 4Se 8 at High Pressure. J Phys Chem Lett 2021; 12:5601-5607. [PMID: 34110170 DOI: 10.1021/acs.jpclett.1c01069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Pressure is a unique thermodynamic variable to explore the phase competitions and novel phases inaccessible at ambient conditions. The resistive switching material GaTa4Se8 displays several quantum phases under pressure, such as a Jeff = 3/2 Mott insulator, a correlated quantum magnetic metal, and d-wave topological superconductivity, which has recently drawn considerable interest. Using high-pressure Raman spectroscopy, X-ray diffraction, extended X-ray absorption, transport measurements, and theoretical calculations, we reveal a complex phase diagram for GaTa4Se8 at pressures exceeding 50 GPa. In this previously unattained pressure regime, GaTa4Se8 ranges from a Mott insulator to a metallic phase and exhibits superconducting phases. In contrast to previous studies, we unveil a hidden correlation between the structural distortion and band gap prior to the insulator-to-metal transition, and the metallic phase shows superconductivity with structural and magnetic properties that are distinctive from the lower-pressure phase. These discoveries highlight that GaTa4Se8 is a unique material to probe novel quantum phases from a structural, metallicity, magnetism, and superconductivity perspective.
Collapse
Affiliation(s)
- Hongshan Deng
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Jianbo Zhang
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Min Yong Jeong
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Dong Wang
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Qingyang Hu
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Shuai Zhang
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Raimundas Sereika
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Takeshi Nakagawa
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Bijuan Chen
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Xia Yin
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Hong Xiao
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Xinguo Hong
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Jichang Ren
- Nano and Heterogeneous Materials Center, School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, People's Republic of China
| | - Myung Joon Han
- Department of Physics, Korea Advanced Institute of Science and Technology, Daejeon 34141, Korea
| | - Jun Chang
- College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710119, People's Republic of China
| | - Hongming Weng
- Beijing National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
| | - Yang Ding
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| | - Hai-Qing Lin
- Beijing Computational Science Research Center, Beijing 100084, People's Republic of China
| | - Ho-Kwang Mao
- Center for High Pressure Science and Technology Advanced Research, Beijing 100094, People's Republic of China
| |
Collapse
|
4
|
Rossi M, Henriquet C, Jacobs J, Donnerer C, Boseggia S, Al-Zein A, Fumagalli R, Yao Y, Vale JG, Hunter EC, Perry RS, Kantor I, Garbarino G, Crichton W, Monaco G, McMorrow DF, Krisch M, Moretti Sala M. Resonant inelastic X-ray scattering of magnetic excitations under pressure. JOURNAL OF SYNCHROTRON RADIATION 2019; 26:1725-1732. [PMID: 31490164 DOI: 10.1107/s1600577519008877] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 06/21/2019] [Indexed: 06/10/2023]
Abstract
Resonant inelastic X-ray scattering (RIXS) is an extremely valuable tool for the study of elementary, including magnetic, excitations in matter. The latest developments of this technique have mostly been aimed at improving the energy resolution and performing polarization analysis of the scattered radiation, with a great impact on the interpretation and applicability of RIXS. Instead, this article focuses on the sample environment and presents a setup for high-pressure low-temperature RIXS measurements of low-energy excitations. The feasibility of these experiments is proved by probing the magnetic excitations of the bilayer iridate Sr3Ir2O7 at pressures up to 12 GPa.
Collapse
Affiliation(s)
- Matteo Rossi
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Christian Henriquet
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Jeroen Jacobs
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Christian Donnerer
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Stefano Boseggia
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Ali Al-Zein
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Roberto Fumagalli
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Yi Yao
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - James G Vale
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Emily C Hunter
- Centre for Science at Extreme Conditions, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JZ, UK
| | - Robin S Perry
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Innokenty Kantor
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Gaston Garbarino
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Wilson Crichton
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Giulio Monaco
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Desmond F McMorrow
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
| | - Michael Krisch
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| | - Marco Moretti Sala
- ESRF - The European Synchrotron, 71 Avenue des Martyrs, CS 40220, F-38043 Grenoble, France
| |
Collapse
|
5
|
Cui D, Gu M, Li C, Duan H, Yan W, Wang P, Li A, Wu D. Interface electron transfer and thickness dependent transport characteristics of La 0.7Sr 0.3VO 3 thin films. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:245002. [PMID: 30865938 DOI: 10.1088/1361-648x/ab0f68] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
La0.7Sr0.3VO3 (LSVO) thin films, 5-30 unit cells (u.c.) in thickness, have been epitaxially deposited on (0 0 1) SrTiO3 (STO) single crystal substrates. Although LSVO is metallic in bulk, insulating behavior is observed, from 2 to 390 K, in LSVO films less than 9 u.c. in thickness, while thicker films show a metal-insulator transition with the critical temperature increasing with the decrease of film thickness. X-ray absorption spectra reveal a charge transfer across the LSVO/STO interface for a continuous increase of V valence in LSVO, as well as a decrease of Ti valence in interfacial STO, with the LSVO film thickness increases. The transport characteristics are discussed in terms of enhanced electron localization due to the reduction of film thickness and V 3d band filling induced by the charge transfer.
Collapse
Affiliation(s)
- Dapeng Cui
- National Laboratory of Solid State Microstructures, Department of Materials Science and Engineering and Jiangsu Key Laboratory for Artificial Functional Materials, Nanjing University, Nanjing, Jiangsu 210093, People's Republic of China
| | | | | | | | | | | | | | | |
Collapse
|
6
|
Vale JG, Boseggia S, Walker HC, Springell RS, Hunter EC, Perry RS, Collins SP, McMorrow DF. Critical fluctuations in the spin-orbit Mott insulator Sr 3Ir 2O 7. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:185803. [PMID: 30721882 DOI: 10.1088/1361-648x/ab0471] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
X-ray magnetic critical scattering measurements and specific heat measurements were performed on the perovskite iridate [Formula: see text]. We find that the magnetic interactions close to the Néel temperature [Formula: see text] are three-dimensional. This contrasts with previous studies which suggest two-dimensional behaviour like Sr2IrO4. Violation of the Harris criterion ([Formula: see text]) means that weak disorder becomes relevant. This leads a rounding of the antiferromagnetic phase transition at [Formula: see text], and modifies the critical exponents relative to the clean system. Specifically, we determine that the critical behaviour of [Formula: see text] is representative of the diluted 3D Ising universality class.
Collapse
Affiliation(s)
- J G Vale
- London Centre for Nanotechnology and Department of Physics and Astronomy, University College London (UCL), Gower Street, London, WC1E 6BT, United Kingdom. Laboratory for Quantum Magnetism, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, CH-1015, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
7
|
Nuclear resonant scattering from 193Ir as a probe of the electronic and magnetic properties of iridates. Sci Rep 2019; 9:5097. [PMID: 30911115 PMCID: PMC6433947 DOI: 10.1038/s41598-019-41130-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2018] [Accepted: 02/08/2019] [Indexed: 11/08/2022] Open
Abstract
The high brilliance of modern synchrotron radiation sources facilitates experiments with high-energy x-rays across a range of disciplines, including the study of the electronic and magnetic correlations using elastic and inelastic scattering techniques. Here we report on Nuclear Resonance Scattering at the 73 keV nuclear level in 193Ir. The transitions between the hyperfine split levels show an untypically high E2/M1 multi-polarity mixing ratio combined with an increased sensitivity to certain changes in the hyperfine field direction compared to non-mixing transitions. The method opens a new way for probing local magnetic and electronic properties of correlated materials containing iridium and provides novel insights into anisotropic magnetism in iridates. In particular, unexpected out-of-plane components of magnetic hyperfine fields and non-zero electric field gradients in Sr2IrO4 have been detected and attributed to the strong spin-orbit interaction in this iridate. Due to the high, 62% natural abundance of the 193Ir isotope, no isotopic enrichment of the samples is required, qualifying the method for a broad range of applications.
Collapse
|
8
|
Cao G, Schlottmann P. The challenge of spin-orbit-tuned ground states in iridates: a key issues review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2018; 81:042502. [PMID: 29353815 DOI: 10.1088/1361-6633/aaa979] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Effects of spin-orbit interactions in condensed matter are an important and rapidly evolving topic. Strong competition between spin-orbit, on-site Coulomb and crystalline electric field interactions in iridates drives exotic quantum states that are unique to this group of materials. In particular, the 'J eff = ½' Mott state served as an early signal that the combined effect of strong spin-orbit and Coulomb interactions in iridates has unique, intriguing consequences. In this Key Issues Review, we survey some current experimental studies of iridates. In essence, these materials tend to defy conventional wisdom: absence of conventional correlations between magnetic and insulating states, avoidance of metallization at high pressures, 'S-shaped' I-V characteristic, emergence of an odd-parity hidden order, etc. It is particularly intriguing that there exist conspicuous discrepancies between current experimental results and theoretical proposals that address superconducting, topological and quantum spin liquid phases. This class of materials, in which the lattice degrees of freedom play a critical role seldom seen in other materials, evidently presents some profound intellectual challenges that call for more investigations both experimentally and theoretically. Physical properties unique to these materials may help unlock a world of possibilities for functional materials and devices. We emphasize that, given the rapidly developing nature of this field, this Key Issues Review is by no means an exhaustive report of the current state of experimental studies of iridates.
Collapse
Affiliation(s)
- Gang Cao
- Department of Physics, University of Colorado at Boulder, Boulder, CO 80309, United States of America
| | | |
Collapse
|
9
|
Lu X, McNally DE, Moretti Sala M, Terzic J, Upton MH, Casa D, Ingold G, Cao G, Schmitt T. Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7}. PHYSICAL REVIEW LETTERS 2017; 118:027202. [PMID: 28128620 DOI: 10.1103/physrevlett.118.027202] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2016] [Indexed: 06/06/2023]
Abstract
We use resonant elastic and inelastic x-ray scattering at the Ir-L_{3} edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} (0≤x≤0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x=0 to 0.05, followed by a transition to two-dimensional short range order between x=0.05 and 0.065. Because of the interactions between the J_{eff}=1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr_{1-x}La_{x})_{3}Ir_{2}O_{7} into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the J_{eff}=1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.
Collapse
Affiliation(s)
- Xingye Lu
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - D E McNally
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - M Moretti Sala
- European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex, France
| | - J Terzic
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
- Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - M H Upton
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - D Casa
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - G Ingold
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
- SwissFEL, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| | - G Cao
- Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA
- Department of Physics, University of Colorado at Boulder, Boulder, Colorado 80309, USA
| | - T Schmitt
- Research Department Synchrotron Radiation and Nanotechnology, Paul Scherrer Institut, CH-5232 Villigen PSI, Switzerland
| |
Collapse
|