We study the structure, magnetization, electrical transport properties and heat capacity of the pyrochlore iridates A2Ir2O7（A=Y, Eu, Bi）. It is found that magnetic frustration and long-range magnetic order coexist i...We study the structure, magnetization, electrical transport properties and heat capacity of the pyrochlore iridates A2Ir2O7（A=Y, Eu, Bi）. It is found that magnetic frustration and long-range magnetic order coexist in Y2Ir2O7 and Eu2Ir2O7, while Bi2Ir2O7 shows magnetic frustration or short-range magnetic order without long-range magnetic order. The former two compounds show insulating behavior. However, the latter one shows metallic behavior. The variations of the radius of A-site ion affect the conduction bandwidth, correlation and Ir-Ir exchange energy, which in turn determine transport properties and magnetic properties. We also find that the antiferromagnetic ordering of pyrochlore iridates is weakly frustrated. The all-in/all-out type of anisotropy based on spin-orbit coupling plays a key role in releasing the frustration.展开更多
The geometrically frustrated iridate La_(3)Ir_(3)O_(11) with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematical...The geometrically frustrated iridate La_(3)Ir_(3)O_(11) with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La_(3)Ir_(3)O_(11) under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P_(c) ~ 38.7 GPa. Synchrotron x-ray diffraction(XRD)experiments indicate the stability of the pristine cubic KSbO_(3)-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P_(c), the bulk modulus gets enhanced and the pressure dependence of bond length d_(Ir-Ir) undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P_(c). Our results demonstrate that the pressure-induced insulating behavior in La_(3)Ir_(3)O_(11) can be assigned to the structural modification, such as the distortion of IrO_6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5 d iridates reported recently.展开更多
AIM:To evaluate the efficiency and safety of an optimized CO2 Laser glaucoma surgery system for laser sclerectomy with iridectomy.METHODS:Rabbit trials were performed to evaluate the efficiency and safety.RESULTS:IOP ...AIM:To evaluate the efficiency and safety of an optimized CO2 Laser glaucoma surgery system for laser sclerectomy with iridectomy.METHODS:Rabbit trials were performed to evaluate the efficiency and safety.RESULTS:IOP was significantly decreased in laser group compared with trabeculectomy group(P<0.05) from 7th postoperative day to 60th day.Compared with trabeculectomy group,histopathology studies confirmed fewer complications and better effects were found in laser group.CONCLUSION:CO2 laser sclerectomy with iridectomy is effective and safe in terms of IOP lowering.展开更多
Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is inv...Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is investigated to gain more insights into the SOC effect in the modification of electronic structure and corresponding magnetic and electrical properties.The high pressure metastable orthorhombic SrIrO_(3)is successfully stabilized by physical and chemical pressures,in which the chemical pressure is induced by Ru doping in Ir site and Mg substitution of Sr position.Detailed structural,magnetic,electrical characterizations and density functional theory(DFT)calculations reveal that the substitution of Ru for Ir renders an enhanced metallic characteristic,while the introduction of Mg into Sr site results in an insulating state with 10.1%negative magnetoresistance at 10 K under 7 T.Theoretical calculations indicate that Ru doping can weaken the SOC effect,leading to the decrease of orbital energy difference between J_(1/2)and J_(3/2),which is favorable for electron transport.On the contrary,Mg doping can enhance the SOC effect,inducing a metal-insulator-transition(MIT).The electronic phase transition is further revealed by DFT calculations,confirming that the strong SOC and electron-electron interactions can lead to the emergence of insulating state.These findings underline the intricate correlations between lattice degrees of freedom and SOC in determining the ground state,which effectively stimulate the physical pressure between like structures by chemical compression.展开更多
Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based...Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based artificial structures play a crucial role owing to their extreme flexibility and tunability in lattice symmetry,chemical composition,and crystal dimensionality.In this article,we present an overview of the recent progress regarding iridate-based artificial structures.We first explicitly introduce several essential concepts in iridates.Then,we illustrate important findings on representative SrIrO_(3)/SrTiO_(3) superlattices,heterostructures comprised of SrIrO3 and magnetic oxides,and their response to external electric-field stimuli.Finally,we comment on existing problems and promising future directions in this exciting field.展开更多
Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0....Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr_(2-x)Pb_(x)IrO_(4). The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr_(2)IrO_(4) matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr_(2)IrO_(4) systems.展开更多
Developing efficient and stable electrocatalysts for the acidic oxygen evolution reaction (OER) is crucial yet challenging due to their sluggish kinetics and potential deactivation in harsh acidic environments.Herein,...Developing efficient and stable electrocatalysts for the acidic oxygen evolution reaction (OER) is crucial yet challenging due to their sluggish kinetics and potential deactivation in harsh acidic environments.Herein,we propose an electronic regulation approach involving the incorporation of trace Pt into SrIrO_(3) perovskite to improve its activity and longevity for OER in acidic media.Both experimental and theoretical results reveal that trace Pt incorporation effectively regulates the electronic structure of SrIrO_(3),lowering the energy barrier of OER and mitigating the Ir overoxidation.The optimized 2%PtSrIrO_(3) electrocatalyst demonstrates an ultralow overpotential of 228 mV at 10 mA cm^(-2)and maintains stable over 50 h in 0.5 M H_(2)SO_(4),rivaling most reported iridate perovskites.As a demonstration,the 2%Pt-SrIrO_(3)||Pt/C based electrolytic cell exhibits high electrochemical performance and robustness for practical acidic water splitting.This protocol offers an attractive strategy for electronic structure manipulation in electrocatalysts towards electrocatalytic applications.展开更多
AIM:To assess the long-term effects of intraocular bevacizumab(Avastin)injections as an adjunctive drug to manage patients with neovascular glaucoma(NVG).METHODS:A retrospective study was conducted consisting of 34 ey...AIM:To assess the long-term effects of intraocular bevacizumab(Avastin)injections as an adjunctive drug to manage patients with neovascular glaucoma(NVG).METHODS:A retrospective study was conducted consisting of 34 eyes with secondary NVG caused by proliferative diabetic retinopathy(n=25),ischemic central retinal vein occlusion(n=8),and retinal ischemia resulting from persistent detachment(n=1)were managed by intraocular injections of bevacizumab(1.25 mg/0.05 m L),in addition to other treatments.The main outcome measure was the change in the degree of iris neovascularization.Secondary outcomes included intraocular pressure and the number of additional interventions or antiglaucoma medications administered after injection.RESULTS:All patients were followed-up for at least 12 mo.At the last follow-up,complete regression of rubeosis irides was detectable in 13(38.2%)eyes and incomplete regression in 21 eyes(61.8%).The mean intraocular pressure was 45.32±7.185 mm Hg at baseline and significantly decreased to 26.15±5.679 mm Hg at the last follow-up visit(P=0.000005).Patients received an average of 4.97 injections.As additional treatments,12 eyes(35%)received laser photocoagulation and 6 eyes(18%)underwent retinocryopexy.No further treatment was needed in 16 eyes(47.1%).CONCLUSION:Intravitreal bevacizumab injection can have a favorable effect in controlling intraocular pressure and pain control in patients with NVG because it decreases the angiogenesis and helps to augment the results of conventional procedures.The primary cause of retinal ischemia should be always targeted.展开更多
Ruddlesden–Popper iridium oxides have attracted considerable interest because of the many proposed novel quantum states that arise from the large spin–orbit coupling of the heavy iridium atoms in them.A prominent ex...Ruddlesden–Popper iridium oxides have attracted considerable interest because of the many proposed novel quantum states that arise from the large spin–orbit coupling of the heavy iridium atoms in them.A prominent example is the single layer Sr2IrO4, in which superconductivity has been proposed under electron doping.However, the synthesis of Sr2IrO4 high quality thin films has been a huge challenge due to the easy formation of impurities associated with different numbers of SrO layers.Thus techniques to optimize the growth of pure phase Sr2IrO4 are urgently required.Here we report the deposition of high quality Sr2IrO4 thin films on both insulating SrTiO3 and conducting SrTiO3:Nb substrates using pulsed laser deposition assisted with reflective high-energy electron diffraction.The optimal deposition temperature of Sr2IrO4 epitaxial films on SrTiO3:Nb substrates is about 90℃ lower than that on SrTiO3 substrates.The electrical transports of high quality Sr2IrO4 films are measured, which follow the three-dimensional Mott variable-range hopping model.The film magnetizations are measured, which show weak ferromagnetism below ~240 K with a saturation magnetization of~ 0.2 μB/Ir at 5 K.This study provides applicable methods to prepare high quality 5 d Sr2IrO4 epitaxial films, which could be extended to other Ruddlesden–Popper phases and potentially help the future study of exotic quantum phenomena in them.展开更多
Recently, 5d transition metal iridates have been reported as promising materials for the manttfacture of exotic quan- tum states. Apart from the semimetallic ground states that have been observed, perovskite SrlrO3 is...Recently, 5d transition metal iridates have been reported as promising materials for the manttfacture of exotic quan- tum states. Apart from the semimetallic ground states that have been observed, perovskite SrlrO3 is also predicted to have a lattice-symmetrically protected topological state in the （110） plane due to its strong： spin-orbil coupling and electron correlation. Compared with non-polar （001）-SflrO3, the especial polarity of （110）-SrIrC）3 undoubtedly adds the： difficulty of fabrication and largely impedes the research on its surface states. Here, we have successfully synthesized high-quality （110）-SflrO3 thin films on （110）-SrTiO3 substrates by reactive molecular beam epitaxy fi^r the first time. Both reflec- tion high-energy electron diffraction pattems and x-ray diffraction measurements suggest the expected orientation and outstanding crystallinity. A （1 × 2） surface reconstruction driven from the surface instabiJity, the. same as that reported in （110）-SrTiO3, is observed. The electric transport measurements uncover that （110）-SrIrO3 exhibits a more prominent semimetallic property in comparison to （001）-SrIrO3.展开更多
Ba_(2)IrO_(4) is a sister compound of the widely investigated Sr_(2)IrO_(4) and has no IrO_(6) octahedral rotation nor net canted antiferromagnetic moment,thus it acts as a system more similar to the high-T_(c) cuprat...Ba_(2)IrO_(4) is a sister compound of the widely investigated Sr_(2)IrO_(4) and has no IrO_(6) octahedral rotation nor net canted antiferromagnetic moment,thus it acts as a system more similar to the high-T_(c) cuprate.In this work,we synthesize the Ba_(2)IrO_(4) epitaxial films by reactive molecular beam epitaxy and study their crystalline structure and transport properties under biaxial compressive strain.High resolution scanning transmission electron microscopy and x-ray diffraction confirm the high quality of films with partial strain relaxation.Under compressive epitaxial strain,the Ba_(2)IrO_(4) exhibits the strain-driven enhancement of the conductivity,consistent with the band gap narrowing and the stronger hybridization of Ir-t_(2g) and O-2p orbitals predicted in the first-principles calculations.展开更多
Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transi...Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition(MIT)region.Rh substitution of Ir is an effective method to induce hole doping into Sr_(3)Ir_(2)O_(7).However,the highest doping level reported in Sr_(3)(Ir_(1-x)Rh_(x))_(2)O_(7)single crystals was only around 3%,which is far from the MIT region.In this paper,we report the successful growth of single crystals of Sr3(Ir_(1-x)Rh_(x))_(2)O_(7)with a doping level of~9%.The samples have been fully characterized,demonstrating the high quality of the single crystals.Transport measurements have been carried out,confirming the tendency of MIT in these samples.The electronic structure has also been examined by angle-resolved photoemission spectroscopy(ARPES)measurements.Our results establish a platform to investigate the heavily hole doped Sr_(3)Ir_(2)O_(7) compound,which also provide new insights into the MIT with hole doping in this material system.展开更多
基金Supported by the National Natural Science Foundation of China(11604071)the Natural Science Foundation of the Education Department of Anhui Province(KJ2016SD49)the Natural Science Foundation of Hefei University(16ZR06ZDB,15RC13,14KY15ZR,2016dtr02)
文摘We study the structure, magnetization, electrical transport properties and heat capacity of the pyrochlore iridates A2Ir2O7（A=Y, Eu, Bi）. It is found that magnetic frustration and long-range magnetic order coexist in Y2Ir2O7 and Eu2Ir2O7, while Bi2Ir2O7 shows magnetic frustration or short-range magnetic order without long-range magnetic order. The former two compounds show insulating behavior. However, the latter one shows metallic behavior. The variations of the radius of A-site ion affect the conduction bandwidth, correlation and Ir-Ir exchange energy, which in turn determine transport properties and magnetic properties. We also find that the antiferromagnetic ordering of pyrochlore iridates is weakly frustrated. The all-in/all-out type of anisotropy based on spin-orbit coupling plays a key role in releasing the frustration.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2018YFA0305704 and 2016YFA0401804)the National Natural Science Foundation of China (Grant Nos. U1632275, U1932152, 11874362, 11704387, 11804344, 11804341, 11974016, U19A2093, and U1832209)+5 种基金the Natural Science Foundation of Anhui ProvinceChina (Grant Nos. 1808085MA06, 2008085QA40, and 1908085QA18)the Users with Excellence Project of Hefei Center CAS (Grant No. 2020HSC-UE015)the Collaborative Innovation Program of Hefei Science Center CAS (Grant No. 2020HSC-CIP014)A portion of this work was supported by the High Magnetic Field Laboratory of Anhui Province under Contract No. AHHM-FX-2020-02Yonghui Zhou was supported by the Youth Innovation Promotion Association CAS (Grant No. 2020443)。
文摘The geometrically frustrated iridate La_(3)Ir_(3)O_(11) with strong spin–orbit coupling and fractional valence was recently predicted to be a quantum spin liquid candidate at ambient conditions. Here, we systematically investigate the evolution of structural and electronic properties of La_(3)Ir_(3)O_(11) under high pressure. Electrical transport measurements reveal an abnormal insulating behavior rather than metallization above a critical pressure P_(c) ~ 38.7 GPa. Synchrotron x-ray diffraction(XRD)experiments indicate the stability of the pristine cubic KSbO_(3)-type structure up to 73.1 GPa. Nevertheless, when the pressure gradually increases across P_(c), the bulk modulus gets enhanced and the pressure dependence of bond length d_(Ir-Ir) undergoes a slope change. Consistent with the XRD data, detailed analyses of Raman spectra reveal an abnormal redshift of Raman mode and a change of Raman intensity around P_(c). Our results demonstrate that the pressure-induced insulating behavior in La_(3)Ir_(3)O_(11) can be assigned to the structural modification, such as the distortion of IrO_6 octahedra. These findings will shed light on the emergent abnormal insulating behavior in other 5 d iridates reported recently.
基金Tianjin Science and Technology Supporting Item, China (No. 10ZCSF00400 and 06YFSZSF00500)
文摘AIM:To evaluate the efficiency and safety of an optimized CO2 Laser glaucoma surgery system for laser sclerectomy with iridectomy.METHODS:Rabbit trials were performed to evaluate the efficiency and safety.RESULTS:IOP was significantly decreased in laser group compared with trabeculectomy group(P<0.05) from 7th postoperative day to 60th day.Compared with trabeculectomy group,histopathology studies confirmed fewer complications and better effects were found in laser group.CONCLUSION:CO2 laser sclerectomy with iridectomy is effective and safe in terms of IOP lowering.
基金supported by the National Natural Science Foundation of China(NSFC,No.22090041)the Guangdong Basic and Applied Basic Research Foundation(No.2022B1515120014)。
文摘Spin-orbit coupling(SOC)plays a vital role in determining the ground state and forming novel electronic states of matter where heavy elements are involved.Here,the prototypical perovskite iridate oxide SrIrO_(3)is investigated to gain more insights into the SOC effect in the modification of electronic structure and corresponding magnetic and electrical properties.The high pressure metastable orthorhombic SrIrO_(3)is successfully stabilized by physical and chemical pressures,in which the chemical pressure is induced by Ru doping in Ir site and Mg substitution of Sr position.Detailed structural,magnetic,electrical characterizations and density functional theory(DFT)calculations reveal that the substitution of Ru for Ir renders an enhanced metallic characteristic,while the introduction of Mg into Sr site results in an insulating state with 10.1%negative magnetoresistance at 10 K under 7 T.Theoretical calculations indicate that Ru doping can weaken the SOC effect,leading to the decrease of orbital energy difference between J_(1/2)and J_(3/2),which is favorable for electron transport.On the contrary,Mg doping can enhance the SOC effect,inducing a metal-insulator-transition(MIT).The electronic phase transition is further revealed by DFT calculations,confirming that the strong SOC and electron-electron interactions can lead to the emergence of insulating state.These findings underline the intricate correlations between lattice degrees of freedom and SOC in determining the ground state,which effectively stimulate the physical pressure between like structures by chemical compression.
基金support from the National Natural Science Foundation of China(NSFC)under grant No.51872155 and 52025024the Beijing Nature Science Foundation(Z200007)+4 种基金the Ministry of Science and Technology of China(2021YFE0107900 and 2021YFA1400300)support from the High Magnetic Field Laboratory of Anhui Province(AHHM-FX-2021-03)the NSFC under Grant No.12104460support from the NSFC under Grant No.92163113 and No.52250418support from the National Science Foundation under Grant No.DMR1848269.
文摘Over the last few years,researches in iridates have developed into an exciting field with the discovery of numerous emergent phenomena,interesting physics,and intriguing functionalities.Among the studies,iridate-based artificial structures play a crucial role owing to their extreme flexibility and tunability in lattice symmetry,chemical composition,and crystal dimensionality.In this article,we present an overview of the recent progress regarding iridate-based artificial structures.We first explicitly introduce several essential concepts in iridates.Then,we illustrate important findings on representative SrIrO_(3)/SrTiO_(3) superlattices,heterostructures comprised of SrIrO3 and magnetic oxides,and their response to external electric-field stimuli.Finally,we comment on existing problems and promising future directions in this exciting field.
基金Project supported by the National Key R&D Program of China (Grant Nos.2022YFA1403203 and 2021YFA1600201)the National Natural Science Foundation of China (Grant Nos.11974356 and 12274414)+1 种基金the Joint Funds of the National Natural Science Foundation of Chinathe Chinese Academy of Sciences Large-Scale Scientific Facility (Grant No.U1932216)。
文摘Group IV element Pb has been selected as the dopant to dope at the Sr site of Sr_(2)IrO_(4). It is exciting to find that the single-phase crystal structure could be maintained with a high Pb doping level of up to x=0.3 in Sr_(2-x)Pb_(x)IrO_(4). The mapping data obtained from energy-dispersive x-ray spectroscopy analyses give solid evidence that the Pb ions are uniformly distributed in the Sr_(2)IrO_(4) matrix. The incorporation of Pb leads to a moderate depression of the canted antiferromagnetic ordering state. The electrical conductivity could be greatly enhanced when the Pb doping content is higher than x=0.2.The present results give a fresh material base to explore new physics in doped Sr_(2)IrO_(4) systems.
基金supported by the financial support from the National Natural Science Foundation of China (No. 22075256&No. 21975229&No. 12262011)the Hainan Provincial Science and Technology Special Found (No. ZDYF2022SHFZ299)+1 种基金the Natural Science Foundation of Guangdong Province (No.2024A1515012235)the Shenzhen Science and Technology Program (No. JCYJ20220530162403008)。
文摘Developing efficient and stable electrocatalysts for the acidic oxygen evolution reaction (OER) is crucial yet challenging due to their sluggish kinetics and potential deactivation in harsh acidic environments.Herein,we propose an electronic regulation approach involving the incorporation of trace Pt into SrIrO_(3) perovskite to improve its activity and longevity for OER in acidic media.Both experimental and theoretical results reveal that trace Pt incorporation effectively regulates the electronic structure of SrIrO_(3),lowering the energy barrier of OER and mitigating the Ir overoxidation.The optimized 2%PtSrIrO_(3) electrocatalyst demonstrates an ultralow overpotential of 228 mV at 10 mA cm^(-2)and maintains stable over 50 h in 0.5 M H_(2)SO_(4),rivaling most reported iridate perovskites.As a demonstration,the 2%Pt-SrIrO_(3)||Pt/C based electrolytic cell exhibits high electrochemical performance and robustness for practical acidic water splitting.This protocol offers an attractive strategy for electronic structure manipulation in electrocatalysts towards electrocatalytic applications.
文摘AIM:To assess the long-term effects of intraocular bevacizumab(Avastin)injections as an adjunctive drug to manage patients with neovascular glaucoma(NVG).METHODS:A retrospective study was conducted consisting of 34 eyes with secondary NVG caused by proliferative diabetic retinopathy(n=25),ischemic central retinal vein occlusion(n=8),and retinal ischemia resulting from persistent detachment(n=1)were managed by intraocular injections of bevacizumab(1.25 mg/0.05 m L),in addition to other treatments.The main outcome measure was the change in the degree of iris neovascularization.Secondary outcomes included intraocular pressure and the number of additional interventions or antiglaucoma medications administered after injection.RESULTS:All patients were followed-up for at least 12 mo.At the last follow-up,complete regression of rubeosis irides was detectable in 13(38.2%)eyes and incomplete regression in 21 eyes(61.8%).The mean intraocular pressure was 45.32±7.185 mm Hg at baseline and significantly decreased to 26.15±5.679 mm Hg at the last follow-up visit(P=0.000005).Patients received an average of 4.97 injections.As additional treatments,12 eyes(35%)received laser photocoagulation and 6 eyes(18%)underwent retinocryopexy.No further treatment was needed in 16 eyes(47.1%).CONCLUSION:Intravitreal bevacizumab injection can have a favorable effect in controlling intraocular pressure and pain control in patients with NVG because it decreases the angiogenesis and helps to augment the results of conventional procedures.The primary cause of retinal ischemia should be always targeted.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51627901 and 11574287)the National Key Research and Development Program of China(Grant No.2016YFA0401004)+1 种基金Hefei Science Center-Chinese Academy of Sciences(Grant No.2016HSC-IU004)the support of the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2016389)
文摘Ruddlesden–Popper iridium oxides have attracted considerable interest because of the many proposed novel quantum states that arise from the large spin–orbit coupling of the heavy iridium atoms in them.A prominent example is the single layer Sr2IrO4, in which superconductivity has been proposed under electron doping.However, the synthesis of Sr2IrO4 high quality thin films has been a huge challenge due to the easy formation of impurities associated with different numbers of SrO layers.Thus techniques to optimize the growth of pure phase Sr2IrO4 are urgently required.Here we report the deposition of high quality Sr2IrO4 thin films on both insulating SrTiO3 and conducting SrTiO3:Nb substrates using pulsed laser deposition assisted with reflective high-energy electron diffraction.The optimal deposition temperature of Sr2IrO4 epitaxial films on SrTiO3:Nb substrates is about 90℃ lower than that on SrTiO3 substrates.The electrical transports of high quality Sr2IrO4 films are measured, which follow the three-dimensional Mott variable-range hopping model.The film magnetizations are measured, which show weak ferromagnetism below ~240 K with a saturation magnetization of~ 0.2 μB/Ir at 5 K.This study provides applicable methods to prepare high quality 5 d Sr2IrO4 epitaxial films, which could be extended to other Ruddlesden–Popper phases and potentially help the future study of exotic quantum phenomena in them.
基金Project supported by the National Key Research and Development Program of the MOST of China(Grant No.2016YFA0300204)the National Key Basic Research Program of China(Grant No.2015CB654901)+2 种基金the National Natural Science Foundation of China(Grant Nos.11574337,11227902,11474147,and11704394)Shanghai Sailing Program(Grant No.17YF1422900)the Award for Outstanding Member in Youth Innovation Promotion Association of the Chinese Academy of Sciences
文摘Recently, 5d transition metal iridates have been reported as promising materials for the manttfacture of exotic quan- tum states. Apart from the semimetallic ground states that have been observed, perovskite SrlrO3 is also predicted to have a lattice-symmetrically protected topological state in the （110） plane due to its strong： spin-orbil coupling and electron correlation. Compared with non-polar （001）-SflrO3, the especial polarity of （110）-SrIrC）3 undoubtedly adds the： difficulty of fabrication and largely impedes the research on its surface states. Here, we have successfully synthesized high-quality （110）-SflrO3 thin films on （110）-SrTiO3 substrates by reactive molecular beam epitaxy fi^r the first time. Both reflec- tion high-energy electron diffraction pattems and x-ray diffraction measurements suggest the expected orientation and outstanding crystallinity. A （1 × 2） surface reconstruction driven from the surface instabiJity, the. same as that reported in （110）-SrTiO3, is observed. The electric transport measurements uncover that （110）-SrIrO3 exhibits a more prominent semimetallic property in comparison to （001）-SrIrO3.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11774153,11861161004,51772143,11974163,and 51672125)the National Key Research and Development Program of China(Grant No.2016YFA0201104)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.0213-14380167 and 0213-14380198)the Hong Kong Research Grants Council(RGC)through the NSFC–RGC Joint Research Scheme,China(Grant No.N PolyU531/18).
文摘Ba_(2)IrO_(4) is a sister compound of the widely investigated Sr_(2)IrO_(4) and has no IrO_(6) octahedral rotation nor net canted antiferromagnetic moment,thus it acts as a system more similar to the high-T_(c) cuprate.In this work,we synthesize the Ba_(2)IrO_(4) epitaxial films by reactive molecular beam epitaxy and study their crystalline structure and transport properties under biaxial compressive strain.High resolution scanning transmission electron microscopy and x-ray diffraction confirm the high quality of films with partial strain relaxation.Under compressive epitaxial strain,the Ba_(2)IrO_(4) exhibits the strain-driven enhancement of the conductivity,consistent with the band gap narrowing and the stronger hybridization of Ir-t_(2g) and O-2p orbitals predicted in the first-principles calculations.
基金supported by the USTC start-up fundthe National Natural Science Foundation of China(Grant Nos.12074358 and 12004363)+2 种基金the Fundamental Research Funds for the Central Universities(Grant Nos.WK3510000008 and WK2030000035)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302802)supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences under Contract No.DEAC02-76SF00515。
文摘Ruddlesden-Popper iridate Sr_(3)Ir_(2)O_(7)is a spin-orbit coupled Mott insulator.Hole doped Sr_(3)Ir_(2)O_(7)provides an ideal platform to study the exotic quantum phenomena that occur near the metal-insulator transition(MIT)region.Rh substitution of Ir is an effective method to induce hole doping into Sr_(3)Ir_(2)O_(7).However,the highest doping level reported in Sr_(3)(Ir_(1-x)Rh_(x))_(2)O_(7)single crystals was only around 3%,which is far from the MIT region.In this paper,we report the successful growth of single crystals of Sr3(Ir_(1-x)Rh_(x))_(2)O_(7)with a doping level of~9%.The samples have been fully characterized,demonstrating the high quality of the single crystals.Transport measurements have been carried out,confirming the tendency of MIT in these samples.The electronic structure has also been examined by angle-resolved photoemission spectroscopy(ARPES)measurements.Our results establish a platform to investigate the heavily hole doped Sr_(3)Ir_(2)O_(7) compound,which also provide new insights into the MIT with hole doping in this material system.
