Pub Date : 2024-08-05DOI: 10.1103/physrevmaterials.8.085801
Fanfan Wang, Jun Yuan, Zhufeng Zhang, Baoan Song, Junhua Zhao, Jincheng Yue, Tian Xu, Jun Zhou
Transition metal carbides, nitrides, and carbonitrides, known as MXenes, exhibit exceptional conductivity, stability, and large specific surface area, rendering them promising candidates for anode materials in rechargeable batteries. Herein, we investigate the electrochemical characteristics of the Janus MXene monolayer, as an anode material of alkali metal ion batteries by using first-principles calculations. The phonon band structure and ab initio molecular dynamics simulations confirm the stability of the Janus monolayer. The mechanical and electrical properties of the Janus monolayer are explored and proved to have good mechanical stability and electrical conductivity. The surface of the Janus monolayer demonstrates the facile adsorption of alkali metal ions and low diffusion barriers. As an anode material, the recyclability of the Janus has been verified in the ion intercalation/deintercalation processes. Furthermore, the theoretical specific capacities and the open-circuit voltages of the Janus monolayer are calculated to be and 2.62 V for Li, and 0.76 V for Na, and and 0.4 V for K, respectively. It presents that the Janus monolayer is a potential anode material of sodium-ion batteries and potassium-ion batteries.
{"title":"Insight into Janus V2COS as anode material of high-performance alkali metal ion battery: Diffusion barrier, recyclability, specific capacity, and open-circuit voltage","authors":"Fanfan Wang, Jun Yuan, Zhufeng Zhang, Baoan Song, Junhua Zhao, Jincheng Yue, Tian Xu, Jun Zhou","doi":"10.1103/physrevmaterials.8.085801","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.085801","url":null,"abstract":"Transition metal carbides, nitrides, and carbonitrides, known as MXenes, exhibit exceptional conductivity, stability, and large specific surface area, rendering them promising candidates for anode materials in rechargeable batteries. Herein, we investigate the electrochemical characteristics of the Janus MXene <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer, as an anode material of alkali metal ion batteries by using first-principles calculations. The phonon band structure and <i>ab initio</i> molecular dynamics simulations confirm the stability of the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer. The mechanical and electrical properties of the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer are explored and proved to have good mechanical stability and electrical conductivity. The surface of the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer demonstrates the facile adsorption of alkali metal ions and low diffusion barriers. As an anode material, the recyclability of the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> has been verified in the ion intercalation/deintercalation processes. Furthermore, the theoretical specific capacities and the open-circuit voltages of the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer are calculated to be <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>165.54</mn><mspace width=\"0.28em\"></mspace><mi>mA</mi><mspace width=\"0.16em\"></mspace><mi mathvariant=\"normal\">h</mi><mtext>/</mtext><mi mathvariant=\"normal\">g</mi></mrow></math> and 2.62 V for Li, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>662.18</mn><mspace width=\"0.28em\"></mspace><mi>mA</mi><mspace width=\"0.16em\"></mspace><mi mathvariant=\"normal\">h</mi><mtext>/</mtext><mi mathvariant=\"normal\">g</mi></mrow></math> and 0.76 V for Na, and <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mn>294.43</mn><mspace width=\"0.28em\"></mspace><mi>mA</mi><mspace width=\"0.16em\"></mspace><mi mathvariant=\"normal\">h</mi><mtext>/</mtext><mi mathvariant=\"normal\">g</mi></mrow></math> and 0.4 V for K, respectively. It presents that the Janus <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">V</mi><mn>2</mn></msub><mi>COS</mi></mrow></math> monolayer is a potential anode material of sodium-ion batteries and potassium-ion batteries.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"65 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141941920","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevmaterials.8.083602
Yao Hu (胡尧), Lewis R. Owen, Helen Y. Playford, Aina Edgren, Sheng Guo, Magnus Hörnqvist Colliander
Severe local lattice distortions (LLDs), originating from the size mismatch among atoms, have been proposed as one of the key mechanisms responsible for the excellent mechanical properties of bcc-structured high-entropy alloys (HEAs). They have also been connected to phase stability, as well as physical properties such as electrical conductivity. Experimental measurements of LLDs are, however, difficult and often ambiguous. Analysis of total scattering data in real space has been proposed to provide a uniquely suitable probe of LLDs, but its widespread application and validation are still limited. We conduct a thorough study of LLD measurements in refractory high-entropy alloys (RHEAs) using small-box pair distribution function (PDF) analysis. We start by reexamining existing literature data using a recently proposed coherent theoretical framework to demonstrate that LLDs in RHEAs can indeed be considered as severe and can be reliably measured even in the absence of known thermal components. We perform total scattering experiments of a typical RHEA (HfNbTaTiZr) using both x-rays and neutrons, and show that real-space PDF analysis of data from different types of radiation gives consistent values of LLDs. The results are also in good agreement with the values derived from reciprocal-space data. Finally, through simulation and analysis of theoretical two-phase PDFs, we demonstrate that the effect of the chemical segregation in the investigated RHEA on the measured LLDs is limited when dealing with comparatively large LLDs. The results show that PDF analysis using small-box modeling provides a fast and reliable tool for measuring LLDs in RHEAs, which makes it ideal for analysis of large data sets from time-resolved in situ measurements.
严重的局部晶格畸变（LLDs）源于原子之间的尺寸不匹配，已被认为是导致 bcc 结构高熵合金（HEAs）具有优异机械性能的关键机制之一。它们还与相稳定性以及导电性等物理性质有关。然而，LLD 的实验测量十分困难，而且往往模棱两可。有人提出分析真实空间中的全散射数据可为 LLDs 提供独一无二的合适探针，但其广泛应用和验证仍然有限。我们利用小盒子对分布函数 (PDF) 分析对难熔高熵合金 (RHEA) 中的 LLD 测量进行了深入研究。我们首先利用最近提出的连贯理论框架重新审查了现有的文献数据，证明 RHEA 中的 LLD 确实可以被认为是严重的，即使在没有已知热成分的情况下也能可靠地测量。我们使用 X 射线和中子对典型的 RHEA（HfNbTaTiZr）进行了全散射实验，结果表明，对来自不同类型辐射的数据进行实空间 PDF 分析可得出一致的 LLD 值。这些结果与根据倒易空间数据得出的值也非常一致。最后，通过对理论两相 PDF 的模拟和分析，我们证明在处理相对较大的 LLD 时，所研究的 RHEA 中的化学偏析对测量 LLD 的影响是有限的。结果表明，利用小盒子建模进行 PDF 分析为测量 RHEA 中的 LLD 提供了一种快速可靠的工具，因此非常适合分析时间分辨原位测量的大型数据集。
{"title":"Quantifying local lattice distortions in refractory high-entropy alloys","authors":"Yao Hu (胡尧), Lewis R. Owen, Helen Y. Playford, Aina Edgren, Sheng Guo, Magnus Hörnqvist Colliander","doi":"10.1103/physrevmaterials.8.083602","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.083602","url":null,"abstract":"Severe local lattice distortions (LLDs), originating from the size mismatch among atoms, have been proposed as one of the key mechanisms responsible for the excellent mechanical properties of bcc-structured high-entropy alloys (HEAs). They have also been connected to phase stability, as well as physical properties such as electrical conductivity. Experimental measurements of LLDs are, however, difficult and often ambiguous. Analysis of total scattering data in real space has been proposed to provide a uniquely suitable probe of LLDs, but its widespread application and validation are still limited. We conduct a thorough study of LLD measurements in refractory high-entropy alloys (RHEAs) using small-box pair distribution function (PDF) analysis. We start by reexamining existing literature data using a recently proposed coherent theoretical framework to demonstrate that LLDs in RHEAs can indeed be considered as severe and can be reliably measured even in the absence of known thermal components. We perform total scattering experiments of a typical RHEA (HfNbTaTiZr) using both x-rays and neutrons, and show that real-space PDF analysis of data from different types of radiation gives consistent values of LLDs. The results are also in good agreement with the values derived from reciprocal-space data. Finally, through simulation and analysis of theoretical two-phase PDFs, we demonstrate that the effect of the chemical segregation in the investigated RHEA on the measured LLDs is limited when dealing with comparatively large LLDs. The results show that PDF analysis using small-box modeling provides a fast and reliable tool for measuring LLDs in RHEAs, which makes it ideal for analysis of large data sets from time-resolved <i>in situ</i> measurements.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"5 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141886635","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-02DOI: 10.1103/physrevmaterials.8.084401
Xuanlin Zhang, Luqi Dong, Yunhao Lu
Two-dimensional (2D) elemental ferroelectricity has recently been confirmed and arouses great interest in exploring new elemental asymmetric structures and their symmetry-breaking related properties. In this study, our density functional theory (DFT) calculations reveal the existence of coupled in-plane and out-of-plane electric polarizations in the group elements (, As). These ferroelectric phases are stabilized through charge transfer between orbitals. The introduction of compressive strain facilitates the transformation from blue phosphorene into -P6 phase with low reaction energy owing to their structural similarity. In addition, strain engineering or atom substitution can effectively reduce the polarization switching barrier. Furthermore, structure exhibits large longitudinal piezoelectric strain coefficients , benefiting from their moderate and flexible character. This discovery not only enriches the family of elemental ferroelectrics but also deepens the understanding of the origin of elemental polarization, offering potential candidates for ferroelectric and piezoelectric applications.
{"title":"Ferroelectricity and piezoelectricity in elemental α-X6 structure","authors":"Xuanlin Zhang, Luqi Dong, Yunhao Lu","doi":"10.1103/physrevmaterials.8.084401","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084401","url":null,"abstract":"Two-dimensional (2D) elemental ferroelectricity has recently been confirmed and arouses great interest in exploring new elemental asymmetric structures and their symmetry-breaking related properties. In this study, our density functional theory (DFT) calculations reveal the existence of coupled in-plane and out-of-plane electric polarizations in the group <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi mathvariant=\"normal\">V</mi></math> elements <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>α</mi><mtext>−</mtext><mrow><mi>X</mi></mrow><mn>6</mn></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi mathvariant=\"italic\">X</mi><mo>=</mo><mi mathvariant=\"normal\">P</mi></mrow></math>, As). These ferroelectric phases are stabilized through charge transfer between <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>p</mi><mi mathvariant=\"normal\">x</mi></msub></math> orbitals. The introduction of compressive strain facilitates the transformation from blue phosphorene into <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>α</mi></math>-P6 phase with low reaction energy owing to their structural similarity. In addition, strain engineering or atom substitution can effectively reduce the polarization switching barrier. Furthermore, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>α</mi><mtext>−</mtext><mrow><mi>X</mi></mrow><mn>6</mn></math> structure exhibits large longitudinal piezoelectric strain coefficients <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>d</mi><mn>11</mn></msub></math>, benefiting from their moderate <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>e</mi><mn>11</mn></msub></math> and flexible character. This discovery not only enriches the family of elemental ferroelectrics but also deepens the understanding of the origin of elemental polarization, offering potential candidates for ferroelectric and piezoelectric applications.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"15 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141886633","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Two-dimensional (2D) materials have attracted vast research interest since the breakthrough discovery of graphene. One major benefit of such systems is the ability to tune the Fermi level through the charge neutrality point between electron and hole doping. Here we show that single layer graphene coupled to the low-density superconductor indium oxide (InO) exhibits two charge neutrality points, each of them representing electronic regions in which the carrier density can be tuned from hole to electron dominated. This is not seen in clean graphene or in a bilayer where the carrier density is extremely low. We suggest that the second charge neutrality point results from regions in the graphene layer just below superconducting islands in InO, where pairing is induced via the proximity effect; gating of this hybrid system therefore allows the tuning from hole to electron superconductivity through an ultralow carrier density regime. We propose this as a “superconducting Dirac point (SDP)” where intravalley scattering is greatly enhanced. Our results suggest that the electronic states around SDP behave like those in a strongly coupled superconductor.
{"title":"Observation of a second Dirac point in a graphene/superconductor bilayer","authors":"Gopi Nath Daptary, Eyal Walach, Udit Khanna, Efrat Shimshoni, Aviad Frydman","doi":"10.1103/physrevmaterials.8.084802","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084802","url":null,"abstract":"Two-dimensional (2D) materials have attracted vast research interest since the breakthrough discovery of graphene. One major benefit of such systems is the ability to tune the Fermi level through the charge neutrality point between electron and hole doping. Here we show that single layer graphene coupled to the low-density superconductor indium oxide (InO) exhibits two charge neutrality points, each of them representing electronic regions in which the carrier density can be tuned from hole to electron dominated. This is not seen in clean graphene or in a bilayer where the carrier density is extremely low. We suggest that the second charge neutrality point results from regions in the graphene layer just below superconducting islands in InO, where pairing is induced via the proximity effect; gating of this hybrid system therefore allows the tuning from hole to electron superconductivity through an ultralow carrier density regime. We propose this as a “superconducting Dirac point (SDP)” where intravalley scattering is greatly enhanced. Our results suggest that the electronic states around SDP behave like those in a strongly coupled superconductor.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"51 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141868025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevmaterials.8.083601
Pui-Wai Ma, Daniel R. Mason, Steven Van Boxel, Sergei L. Dudarev
Evolution of nanocrystalline (NC) tungsten under radiation exposure is investigated by atomic scale simulations in the low temperature high dose limit. Statistical analysis of samples containing at least a million atoms, with grain size varying from 5 nm to 20 nm, shows that the pattern of microstructural evolution of a NC material differs significantly from that of a single crystal. The high resistance to swelling in the low grain size limit stems from a combined effect of the initial excess volume of atomic configurations at grain boundaries and high integral volume of grain boundary defect-denuded zones. Grain boundaries annihilate defects through the rearrangement of their local atomic configurations acting as fluctuating dynamic sinks for defects. Grain size distribution slowly broadens as a function of dose, delaying the onset of an asymptotic radiation-driven steady state in comparison with a single crystalline material. Spatial limitations imposed by the size and topology of grains prevent the formation of a percolating dislocation network, resulting in only isolated dislocation loops being retained in the microstructure even at high radiation exposure.
{"title":"Nanocrystalline tungsten at high radiation exposure","authors":"Pui-Wai Ma, Daniel R. Mason, Steven Van Boxel, Sergei L. Dudarev","doi":"10.1103/physrevmaterials.8.083601","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.083601","url":null,"abstract":"Evolution of nanocrystalline (NC) tungsten under radiation exposure is investigated by atomic scale simulations in the low temperature high dose limit. Statistical analysis of samples containing at least a million atoms, with grain size varying from 5 nm to 20 nm, shows that the pattern of microstructural evolution of a NC material differs significantly from that of a single crystal. The high resistance to swelling in the low grain size limit stems from a combined effect of the initial excess volume of atomic configurations at grain boundaries and high integral volume of grain boundary defect-denuded zones. Grain boundaries annihilate defects through the rearrangement of their local atomic configurations acting as fluctuating dynamic sinks for defects. Grain size distribution slowly broadens as a function of dose, delaying the onset of an asymptotic radiation-driven steady state in comparison with a single crystalline material. Spatial limitations imposed by the size and topology of grains prevent the formation of a percolating dislocation network, resulting in only isolated dislocation loops being retained in the microstructure even at high radiation exposure.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"13 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141867909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-01DOI: 10.1103/physrevmaterials.8.084801
Nawaraj Paudel, Chiara Tarantini, Shreyas Balachandran, William L. Starch, Peter J. Lee, David C. Larbalestier
<math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> conductors are important candidates for high-field magnets for particle accelerators, and they continue to be widely used for many laboratory and nuclear magnetic resonance magnets. However, the critical current density, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>J</mi><mi>c</mi></msub></math>, of present <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> conductors declines swiftly above 12–15 T. State-of-the-art Ta- and Ti-doped strands exhibit upper critical field, <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math>, values of ∼24–26.5 T (4.2 K) and do not reach the Future Circular Collider target <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>J</mi><mi>c</mi></msub></math>, which serves as the present stretch target for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> development. As recently demonstrated, to meet this goal requires enhanced vortex pinning but an independent and supplementary approach is to significantly enhance <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math>. In this study, we have arc melted multiple Nb alloys with added Hf, Zr, Ta, and Ti and drawn them successfully into monofilament wires to investigate the possibilities of <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math> enhancement through alloying. <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo>(</mo><mi>T</mi><mo>)</mo></math> was measured for all samples in fields up to 16 T and some up to 31 T. We have found that all alloys show good agreement with the standard Werthamer, Helfand, and Hohenberg fitting procedure without the need to adjust the paramagnetic limitation parameter (<i>α</i>) and spin-orbit scattering parameter <math xmlns="http://www.w3.org/1998/Math/MathML"><mo>(</mo><msub><mi>λ</mi><mi>so</mi></msub><mo>)</mo></math>. The evaluation of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>d</mi><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo>/</mo><mi>d</mi><mi>T</mi></mrow></math> near <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>T</mi><mi>c</mi></msub></math>, which is proportional to the electronic specific heat coefficient <i>γ</i> and the normal state resistivity <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>ρ</mi><mi mathvariant="normal">n</mi></msub></math>, allows a better understanding of the induced disorder introduced by alloying in the A15 phase. So far, we have observed that Hf alloying of pure Nb can enhance <math xmln
{"title":"Influence of Nb alloying on Nb recrystallization and the upper critical field of Nb3Sn","authors":"Nawaraj Paudel, Chiara Tarantini, Shreyas Balachandran, William L. Starch, Peter J. Lee, David C. Larbalestier","doi":"10.1103/physrevmaterials.8.084801","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.084801","url":null,"abstract":"<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> conductors are important candidates for high-field magnets for particle accelerators, and they continue to be widely used for many laboratory and nuclear magnetic resonance magnets. However, the critical current density, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>J</mi><mi>c</mi></msub></math>, of present <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> conductors declines swiftly above 12–15 T. State-of-the-art Ta- and Ti-doped strands exhibit upper critical field, <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math>, values of ∼24–26.5 T (4.2 K) and do not reach the Future Circular Collider target <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>J</mi><mi>c</mi></msub></math>, which serves as the present stretch target for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi mathvariant=\"normal\">Nb</mi><mn>3</mn></msub><mi>Sn</mi></mrow></math> development. As recently demonstrated, to meet this goal requires enhanced vortex pinning but an independent and supplementary approach is to significantly enhance <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math>. In this study, we have arc melted multiple Nb alloys with added Hf, Zr, Ta, and Ti and drawn them successfully into monofilament wires to investigate the possibilities of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub></math> enhancement through alloying. <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo>(</mo><mi>T</mi><mo>)</mo></math> was measured for all samples in fields up to 16 T and some up to 31 T. We have found that all alloys show good agreement with the standard Werthamer, Helfand, and Hohenberg fitting procedure without the need to adjust the paramagnetic limitation parameter (<i>α</i>) and spin-orbit scattering parameter <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mo>(</mo><msub><mi>λ</mi><mi>so</mi></msub><mo>)</mo></math>. The evaluation of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>d</mi><msub><mi>H</mi><mrow><mi>c</mi><mn>2</mn></mrow></msub><mo>/</mo><mi>d</mi><mi>T</mi></mrow></math> near <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi>c</mi></msub></math>, which is proportional to the electronic specific heat coefficient <i>γ</i> and the normal state resistivity <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>ρ</mi><mi mathvariant=\"normal\">n</mi></msub></math>, allows a better understanding of the induced disorder introduced by alloying in the A15 phase. So far, we have observed that Hf alloying of pure Nb can enhance <math xmln","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"88 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141868024","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1103/physrevmaterials.8.074201
Mohammad Shafiei, Farhad Fazileh, François M. Peeters, Milorad V. Milošević
We explore the effect of thickness, magnetization direction, strain, and gating on the topological quantum phase transition of a thin-film magnetic topological insulator. Reducing the film thickness to the ultrathin regime couples the edge states on the two surfaces, opening a gap known as the hybridization gap, and causing a phase transition from a topological insulator to a normal insulator (NI). An out-of-plane/in-plane magnetization of size proportional to the hybridization gap triggers a phase transition from a normal insulator state to a quantum anomalous Hall (QAH)/semimetal state. A magnetization tilt by angle from the out-of-plane axis influences the topological phase transition in a way that for sufficiently large , no phase transition from NI to QAH can be observed regardless of the sample thickness or magnetization, and for close to the system transits to a semimetal phase. Furthermore, we demonstrate that compressive/tensile strain can be used to decrease/increase the magnetization threshold for the topological phase transition. Finally, we reveal the effect of a vertical potential acting on the film, be it due to the substrate or applied gating, which breaks inversion symmetry and raises the magnetization threshold for the transition from NI to QAH state.
我们探索了厚度、磁化方向、应变和门控对薄膜磁性拓扑绝缘体拓扑量子相变的影响。将薄膜厚度减小到超薄状态会耦合两个表面上的边缘态，打开一个被称为杂化间隙的缺口，导致从拓扑绝缘体到正常绝缘体（NI）的相变。与杂化间隙大小成正比的平面外/平面内磁化会引发从正常绝缘体态到量子反常霍尔（QAH）/半金属态的相变。与平面外轴线成θ角的磁化倾斜会影响拓扑相变，在θ足够大的情况下，无论样品厚度或磁化程度如何，都无法观察到从NI到QAH的相变，而当θ接近π/2时，系统会过渡到半金属相。此外，我们还证明了压缩/拉伸应变可用于降低/提高拓扑相变的磁化阈值。最后，我们揭示了作用在薄膜上的垂直电势（无论是由于基底还是外加门控）的影响，它打破了反转对称性，提高了从 NI 到 QAH 状态转变的磁化阈值。
{"title":"Tuning the quantum phase transition of an ultrathin magnetic topological insulator","authors":"Mohammad Shafiei, Farhad Fazileh, François M. Peeters, Milorad V. Milošević","doi":"10.1103/physrevmaterials.8.074201","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074201","url":null,"abstract":"We explore the effect of thickness, magnetization direction, strain, and gating on the topological quantum phase transition of a thin-film magnetic topological insulator. Reducing the film thickness to the ultrathin regime couples the edge states on the two surfaces, opening a gap known as the hybridization gap, and causing a phase transition from a topological insulator to a normal insulator (NI). An out-of-plane/in-plane magnetization of size proportional to the hybridization gap triggers a phase transition from a normal insulator state to a quantum anomalous Hall (QAH)/semimetal state. A magnetization tilt by angle <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>θ</mi></math> from the out-of-plane axis influences the topological phase transition in a way that for sufficiently large <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>θ</mi></math>, no phase transition from NI to QAH can be observed regardless of the sample thickness or magnetization, and for <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>θ</mi></math> close to <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>π</mi><mo>/</mo><mn>2</mn></mrow></math> the system transits to a semimetal phase. Furthermore, we demonstrate that compressive/tensile strain can be used to decrease/increase the magnetization threshold for the topological phase transition. Finally, we reveal the effect of a vertical potential acting on the film, be it due to the substrate or applied gating, which breaks inversion symmetry and raises the magnetization threshold for the transition from NI to QAH state.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"40 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-25DOI: 10.1103/physrevmaterials.8.074805
Jihun Park, Jarryd A. Horn, Dylan J. Kirsch, Rohit K. Pant, Hyeok Yoon, Sungha Baek, Suchismita Sarker, Apurva Mehta, Xiaohang Zhang, Seunghun Lee, Richard Greene, Johnpierre Paglione, Ichiro Takeuchi
The Bi-Ni binary system has been of interest due to possible unconventional superconductivity aroused therein, such as time-reversal symmetry breaking in Bi/Ni bilayers or the coexistence of superconductivity and ferromagnetism in crystals. While Ni acts as a ferromagnetic element in such systems, the role of the strong spin-orbit coupling element Bi in superconductivity has remained unexplored. In this work, we systematically studied the effects of Bi stoichiometry on the superconductivity of thin films () fabricated via a composition-spread approach. The superconducting phase map of thin films exhibited a superconducting composition region attributable to the intermetallic phase with different amounts of excess Bi, revealed by synchrotron x-ray diffraction analysis. Interestingly, the mixed-phase region with and Bi showed unusual increases in the superconducting transition temperature and residual resistance ratio as more Bi impurities were included, with the maximum () observed at . A correlation analysis of structural, electrical, and magneto-transport characteristics across the composition variation revealed that the unusual superconducting “dome” is due to two competing roles of Bi: impurity scattering and carrier doping. We found that the carrier doping effect is dominant in the mild doping regime , while impurity scattering becomes more pronounced at larger Bi stoichiometry.
铋镍二元系统一直备受关注，因为其中可能产生非常规超导性，例如铋镍双层膜中的时间反转对称破缺或铋镍晶体中的超导性与铁磁性共存。虽然镍在此类体系中充当了铁磁元素，但强自旋轨道耦合元素 Bi 在超导中的作用仍未得到探索。在这项工作中，我们系统地研究了 Bi 的化学计量对通过成分分布法制造的 BixNi1-x 薄膜（x≈0.5-0.9）超导性的影响。通过同步辐射 X 射线衍射分析，BixNi1-x 薄膜的超导相图显示出一个超导成分区域，该区域可归因于过量 Bi 的金属间 Bi3Ni 相。有趣的是，Bi3Ni 和 Bi 的混合相区随着 Bi 杂质含量的增加，超导转变温度和残余电阻比也出现了不同寻常的增长，在 x≈0.79 时观察到了最大 Tc（=4.2K）。对整个成分变化过程中的结构、电学和磁传输特性进行的相关分析表明，不寻常的超导 "圆顶 "是由于铋的两种相互竞争的作用：杂质散射和载流子掺杂。我们发现，载流子掺杂效应在温和掺杂体系（0.74≤x≤0.79）中占主导地位，而杂质散射在较大的铋化学计量时变得更加明显。
{"title":"Superconducting phase diagram in BixNi1–x thin films: The effects of Bi stoichiometry on superconductivity","authors":"Jihun Park, Jarryd A. Horn, Dylan J. Kirsch, Rohit K. Pant, Hyeok Yoon, Sungha Baek, Suchismita Sarker, Apurva Mehta, Xiaohang Zhang, Seunghun Lee, Richard Greene, Johnpierre Paglione, Ichiro Takeuchi","doi":"10.1103/physrevmaterials.8.074805","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074805","url":null,"abstract":"The Bi-Ni binary system has been of interest due to possible unconventional superconductivity aroused therein, such as time-reversal symmetry breaking in Bi/Ni bilayers or the coexistence of superconductivity and ferromagnetism in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> crystals. While Ni acts as a ferromagnetic element in such systems, the role of the strong spin-orbit coupling element Bi in superconductivity has remained unexplored. In this work, we systematically studied the effects of Bi stoichiometry on the superconductivity of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mi>x</mi></msub><msub><mi>Ni</mi><mrow><mn>1</mn><mo>–</mo><mi>x</mi></mrow></msub></mrow></math> thin films (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>≈</mo><mn>0.5</mn><mo>–</mo><mn>0.9</mn></mrow></math>) fabricated via a composition-spread approach. The superconducting phase map of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mi>x</mi></msub><msub><mi>Ni</mi><mrow><mn>1</mn><mo>–</mo><mi>x</mi></mrow></msub></mrow></math> thin films exhibited a superconducting composition region attributable to the intermetallic <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> phase with different amounts of excess Bi, revealed by synchrotron x-ray diffraction analysis. Interestingly, the mixed-phase region with <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Bi</mi><mn>3</mn></msub><mi>Ni</mi></mrow></math> and Bi showed unusual increases in the superconducting transition temperature and residual resistance ratio as more Bi impurities were included, with the maximum <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>T</mi><mi mathvariant=\"normal\">c</mi></msub></math> (<math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>=</mo><mn>4.2</mn><mspace width=\"0.28em\"></mspace><mi mathvariant=\"normal\">K</mi></mrow></math>) observed at <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>x</mi><mo>≈</mo><mn>0.79</mn></mrow></math>. A correlation analysis of structural, electrical, and magneto-transport characteristics across the composition variation revealed that the unusual superconducting “dome” is due to two competing roles of Bi: impurity scattering and carrier doping. We found that the carrier doping effect is dominant in the mild doping regime <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mo>(</mo><mn>0.74</mn><mo>≤</mo><mi>x</mi><mo>≤</mo><mn>0.79</mn><mo>)</mo></mrow></math>, while impurity scattering becomes more pronounced at larger Bi stoichiometry.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"18 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-07-24DOI: 10.1103/physrevmaterials.8.074604
Jing Huang, Jun Kang
Ternary nitride is a promising candidate to fill the “green gap” of nitride-based light-emitting diodes. The coexistence of two different valence cations offers a unique tunability on its electronic properties through controlling the degree of cation site ordering without a concomitant change in stoichiometry. In this work, the structural and electronic properties of cation-disordered are studied through a combination of density functional theory calculations, cluster expansion, and Monte Carlo simulations. The order-disorder phase transition is analyzed, and the short-range and long-range order parameters quantifying the degree of disorder are calculated. A strong correlation between the two parameters is observed, indicating the absence of the octet-rule-conserving disorder. Cation disorder has two main effects on the electronic properties of . One is the reduction of the band gap, and the other is the strong localization of valence band edge states. Further analysis showed that the localization is a consequence of the weak interatomic coupling between the N atoms and the disorder-induced fluctuation of the local electrostatic potentials on the N atoms. These results could be helpful for the understanding of disorder effects in , as well as the tuning of its properties through the control of cation ordering.
三元氮化物 MgSnN2 有望填补氮化物发光二极管的 "绿色空白"。两种不同价位的阳离子共存，通过控制阳离子位点有序化程度，为其电子特性提供了独特的可调谐性，而无需同时改变化学计量学。在这项研究中，我们结合密度泛函理论计算、簇扩展和蒙特卡罗模拟，研究了阳离子失序 MgSnN2 的结构和电子特性。分析了有序-无序相变，并计算了量化无序程度的短程和长程有序参数。观察到这两个参数之间存在很强的相关性，表明不存在八分位守恒无序。阳离子无序对 MgSnN2 的电子特性有两个主要影响。一个是带隙的减小，另一个是价带边缘态的强烈局域化。进一步的分析表明，这种局域化是 N 原子间微弱的原子间耦合和无序引起的 N 原子局部静电势波动的结果。这些结果有助于理解 MgSnN2 中的无序效应，以及通过控制阳离子有序来调整其性质。
{"title":"Cation disorder in MgSnN2 and its effects on the electronic properties","authors":"Jing Huang, Jun Kang","doi":"10.1103/physrevmaterials.8.074604","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074604","url":null,"abstract":"Ternary nitride <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math> is a promising candidate to fill the “green gap” of nitride-based light-emitting diodes. The coexistence of two different valence cations offers a unique tunability on its electronic properties through controlling the degree of cation site ordering without a concomitant change in stoichiometry. In this work, the structural and electronic properties of cation-disordered <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math> are studied through a combination of density functional theory calculations, cluster expansion, and Monte Carlo simulations. The order-disorder phase transition is analyzed, and the short-range and long-range order parameters quantifying the degree of disorder are calculated. A strong correlation between the two parameters is observed, indicating the absence of the octet-rule-conserving disorder. Cation disorder has two main effects on the electronic properties of <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math>. One is the reduction of the band gap, and the other is the strong localization of valence band edge states. Further analysis showed that the localization is a consequence of the weak interatomic coupling between the N atoms and the disorder-induced fluctuation of the local electrostatic potentials on the N atoms. These results could be helpful for the understanding of disorder effects in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>MgSnN</mi><mn>2</mn></msub></math>, as well as the tuning of its properties through the control of cation ordering.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"55 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An appealing direction to change the properties of strongly correlated materials is to induce nonequilibrium steady states by the application of a direct current. While access to these novel states is of high scientific interest, Joule heating due to current flow often constitutes a hurdle to identify nonthermal effects. The biggest challenge usually resides in measuring accurately the temperature of a sample subjected to direct current, and to use probes that give direct information of the material. In this work, we exploit the simultaneous measurement of electrical transport and magnetization to probe nonequilibrium steady states in . In order to reveal nonthermal current-induced effects, we employ a simple model of Joule self-heating to remove the effects of heating and discuss the importance of temperature inhomogeneity within the sample. Our approach provides a solid basis for investigating current-induced phenomena in highly resistive materials.
{"title":"Challenges in extracting nonlinear current-induced phenomena in Ca2RuO4","authors":"Giordano Mattoni, Kazumi Fukushima, Shingo Yonezawa, Fumihiko Nakamura, Yoshiteru Maeno","doi":"10.1103/physrevmaterials.8.074411","DOIUrl":"https://doi.org/10.1103/physrevmaterials.8.074411","url":null,"abstract":"An appealing direction to change the properties of strongly correlated materials is to induce nonequilibrium steady states by the application of a direct current. While access to these novel states is of high scientific interest, Joule heating due to current flow often constitutes a hurdle to identify nonthermal effects. The biggest challenge usually resides in measuring accurately the temperature of a sample subjected to direct current, and to use probes that give direct information of the material. In this work, we exploit the simultaneous measurement of electrical transport and magnetization to probe nonequilibrium steady states in <math xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><msub><mi>Ca</mi><mn>2</mn></msub><mi>Ru</mi><msub><mi mathvariant=\"normal\">O</mi><mn>4</mn></msub></mrow></math>. In order to reveal nonthermal current-induced effects, we employ a simple model of Joule self-heating to remove the effects of heating and discuss the importance of temperature inhomogeneity within the sample. Our approach provides a solid basis for investigating current-induced phenomena in highly resistive materials.","PeriodicalId":20545,"journal":{"name":"Physical Review Materials","volume":"63 1","pages":""},"PeriodicalIF":3.4,"publicationDate":"2024-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141783156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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