A. Osman, J. Simon, A. Bengtsson, S. Kosen, P. Krantz, D. P. Lozano, M. Scigliuzzo, P. Delsing, J. Bylander, A. Fadavi Roudsari
We introduce a simplified fabrication technique for Josephson junctions and demonstrate superconducting Xmon qubits with $T_1$ relaxation times averaging above 50$~mu$s ($Q>$1.5$times$ 10$^6$). Current shadow-evaporation techniques for aluminum-based Josephson junctions require a separate lithography step to deposit a patch that makes a galvanic, superconducting connection between the junction electrodes and the circuit wiring layer. The patch connection eliminates parasitic junctions, which otherwise contribute significantly to dielectric loss. In our patch-integrated cross-type (PICT) junction technique, we use one lithography step and one vacuum cycle to evaporate both the junction electrodes and the patch. In a study of more than 3600 junctions, we show an average resistance variation of 3.7$%$ on a wafer that contains forty 0.5$times$0.5-cm$^2$ chips, with junction areas ranging between 0.01 and 0.16 $mu$m$^2$. The average on-chip spread in resistance is 2.7$%$, with 20 chips varying between 1.4 and 2$%$. For the junction sizes used for transmon qubits, we deduce a wafer-level transition-frequency variation of 1.7-2.5$%$. We show that 60-70$%$ of this variation is attributed to junction-area fluctuations, while the rest is caused by tunnel-junction inhomogeneity. Such high frequency predictability is a requirement for scaling-up the number of qubits in a quantum computer.
{"title":"Simplified Josephson-junction fabrication process for reproducibly high-performance superconducting qubits","authors":"A. Osman, J. Simon, A. Bengtsson, S. Kosen, P. Krantz, D. P. Lozano, M. Scigliuzzo, P. Delsing, J. Bylander, A. Fadavi Roudsari","doi":"10.1063/5.0037093","DOIUrl":"https://doi.org/10.1063/5.0037093","url":null,"abstract":"We introduce a simplified fabrication technique for Josephson junctions and demonstrate superconducting Xmon qubits with $T_1$ relaxation times averaging above 50$~mu$s ($Q>$1.5$times$ 10$^6$). Current shadow-evaporation techniques for aluminum-based Josephson junctions require a separate lithography step to deposit a patch that makes a galvanic, superconducting connection between the junction electrodes and the circuit wiring layer. The patch connection eliminates parasitic junctions, which otherwise contribute significantly to dielectric loss. In our patch-integrated cross-type (PICT) junction technique, we use one lithography step and one vacuum cycle to evaporate both the junction electrodes and the patch. In a study of more than 3600 junctions, we show an average resistance variation of 3.7$%$ on a wafer that contains forty 0.5$times$0.5-cm$^2$ chips, with junction areas ranging between 0.01 and 0.16 $mu$m$^2$. The average on-chip spread in resistance is 2.7$%$, with 20 chips varying between 1.4 and 2$%$. For the junction sizes used for transmon qubits, we deduce a wafer-level transition-frequency variation of 1.7-2.5$%$. We show that 60-70$%$ of this variation is attributed to junction-area fluctuations, while the rest is caused by tunnel-junction inhomogeneity. Such high frequency predictability is a requirement for scaling-up the number of qubits in a quantum computer.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73905181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-10DOI: 10.21203/rs.3.rs-105803/v1
C. Cho, J. Lyu, C. Ng, J. J. He, T. Abdel-Baset, M. Abdel-Hafiez, R. Lortz
We present magnetic torque, specific heat and thermal expansion measurements combined with a piezo rotary positioner of the bulk transition metal dichalcogenide (TMD) superconductor NbS2 in high magnetic fields applied strictly parallel to its layer structure. The upper critical field of superconducting TMDs in the 2D form is known to be dramatically enhanced by a special form of Ising spin orbit coupling. This Ising superconductivity is very robust against the Pauli limit for superconductivity. We find that superconductivity beyond the Pauli limit still exists in bulk single crystals of NbS2. However, the comparison of our upper critical field transition line with numerical simulations rather points to the development of a Fulde-Ferrell-Larkin-Ovchinnikov state above the Pauli limit as a cause. This is also consistent with the observation of a magnetic field driven phase transition in the thermodynamic quantities within the superconducting state near the Pauli limit.
{"title":"Superconductivity beyond Pauli's limit in bulk NbS2: Evidence for the Fulde-Ferrell-Larkin-Ovchinnikov state","authors":"C. Cho, J. Lyu, C. Ng, J. J. He, T. Abdel-Baset, M. Abdel-Hafiez, R. Lortz","doi":"10.21203/rs.3.rs-105803/v1","DOIUrl":"https://doi.org/10.21203/rs.3.rs-105803/v1","url":null,"abstract":"\u0000 We present magnetic torque, specific heat and thermal expansion measurements combined with a piezo rotary positioner of the bulk transition metal dichalcogenide (TMD) superconductor NbS2 in high magnetic fields applied strictly parallel to its layer structure. The upper critical field of superconducting TMDs in the 2D form is known to be dramatically enhanced by a special form of Ising spin orbit coupling. This Ising superconductivity is very robust against the Pauli limit for superconductivity. We find that superconductivity beyond the Pauli limit still exists in bulk single crystals of NbS2. However, the comparison of our upper critical field transition line with numerical simulations rather points to the development of a Fulde-Ferrell-Larkin-Ovchinnikov state above the Pauli limit as a cause. This is also consistent with the observation of a magnetic field driven phase transition in the thermodynamic quantities within the superconducting state near the Pauli limit.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81486174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-09DOI: 10.1103/PhysRevB.102.180508
M. Žemlička, M. Kopčík, P. Szab'o, T. Samuely, J. Kačmarčík, P. Neilinger, M. Grajcar, P. Samuely
Superconductor insulator transition in transverse magnetic field is studied in the highly disordered MoC film with the product of the Fermi momentum and the mean free path $k_F*l$ close to unity. Surprisingly, the Zeeman paramagnetic effects dominate over orbital coupling on both sides of the transition. In superconducting state it is evidenced by a high upper critical magnetic field $B_{c2}$, by its square root dependence on temperature, as well as by the Zeeman splitting of the quasiparticle density of states (DOS) measured by scanning tunneling microscopy. At $B_{c2}$ a logarithmic anomaly in DOS is observed. This anomaly is further enhanced in increasing magnetic field, which is explained by the Zeeman splitting of the Altshuler-Aronov DOS driving the system into a more insulating or resistive state. Spin dependent Altshuler-Aronov correction is also needed to explain the transport behavior above $B_{c2}$.
{"title":"Zeeman-driven superconductor-insulator transition in strongly disordered MoC films: Scanning tunneling microscopy and transport studies in a transverse magnetic field","authors":"M. Žemlička, M. Kopčík, P. Szab'o, T. Samuely, J. Kačmarčík, P. Neilinger, M. Grajcar, P. Samuely","doi":"10.1103/PhysRevB.102.180508","DOIUrl":"https://doi.org/10.1103/PhysRevB.102.180508","url":null,"abstract":"Superconductor insulator transition in transverse magnetic field is studied in the highly disordered MoC film with the product of the Fermi momentum and the mean free path $k_F*l$ close to unity. Surprisingly, the Zeeman paramagnetic effects dominate over orbital coupling on both sides of the transition. In superconducting state it is evidenced by a high upper critical magnetic field $B_{c2}$, by its square root dependence on temperature, as well as by the Zeeman splitting of the quasiparticle density of states (DOS) measured by scanning tunneling microscopy. At $B_{c2}$ a logarithmic anomaly in DOS is observed. This anomaly is further enhanced in increasing magnetic field, which is explained by the Zeeman splitting of the Altshuler-Aronov DOS driving the system into a more insulating or resistive state. Spin dependent Altshuler-Aronov correction is also needed to explain the transport behavior above $B_{c2}$.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83479115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-04DOI: 10.1103/PHYSREVB.103.014511
S. Sundar, S. Dunsiger, S. Gheidi, K. Akella, A. M. Cot'e, H. U. Özdemir, N. R. Lee-Hone, D. Broun, E. Mun, F. Honda, Y. Sato, T. Koizumi, R. Settai, Y. Hirose, I. Bonalde, J. Sonier
We report a $mu$SR investigation of a non-centrosymmetric superconductor (LaNiC$_2$) in single crystal form. Compared to previous $mu$SR studies of non-centrosymmetric superconducting polycrystalline and powder samples, the unambiguous orientation of single crystals enables a simultaneous determination of the absolute value of the magnetic penetration depth and the vortex core size from measurements that probe the magnetic field distribution in the vortex state. The magnetic field dependence of these quantities unambiguously demonstrates the presence of two nodeless superconducting energy gaps. In addition, we detect weak internal magnetic fields in the superconducting phase, confirming earlier $mu$SR evidence for a time-reversal symmetry breaking superconducting state. Our results suggest that Cooper pairing in LaNiC$_2$ is characterized by the same interorbital equal-spin pairing model introduced to describe the pairing state in the centrosymmetric superconductor LaNiGa$_2$.
{"title":"Two-gap time reversal symmetry breaking superconductivity in noncentrosymmetric \u0000LaNiC2","authors":"S. Sundar, S. Dunsiger, S. Gheidi, K. Akella, A. M. Cot'e, H. U. Özdemir, N. R. Lee-Hone, D. Broun, E. Mun, F. Honda, Y. Sato, T. Koizumi, R. Settai, Y. Hirose, I. Bonalde, J. Sonier","doi":"10.1103/PHYSREVB.103.014511","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.014511","url":null,"abstract":"We report a $mu$SR investigation of a non-centrosymmetric superconductor (LaNiC$_2$) in single crystal form. Compared to previous $mu$SR studies of non-centrosymmetric superconducting polycrystalline and powder samples, the unambiguous orientation of single crystals enables a simultaneous determination of the absolute value of the magnetic penetration depth and the vortex core size from measurements that probe the magnetic field distribution in the vortex state. The magnetic field dependence of these quantities unambiguously demonstrates the presence of two nodeless superconducting energy gaps. In addition, we detect weak internal magnetic fields in the superconducting phase, confirming earlier $mu$SR evidence for a time-reversal symmetry breaking superconducting state. Our results suggest that Cooper pairing in LaNiC$_2$ is characterized by the same interorbital equal-spin pairing model introduced to describe the pairing state in the centrosymmetric superconductor LaNiGa$_2$.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75970450","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-04DOI: 10.1103/PHYSREVB.103.054501
Manasi Mandal, K. P. Sajilesh, R. R. Chowdhury, D. Singh, P. Biswas, A. Hillier, R. P. Singh
The topologically non-trivial band structure of A15 compounds has drawn attention owing to the possible realization of topological superconductivity. Here, we report a microscopic investigation of the superconducting ground state in A15 compound Ti$_{3}$X (X = Ir, Sb) by muon spectroscopy measurements. Zero field muon measurements have shown that time-reversal symmetry is preserved in these materials. Furthermore, specific heat and a transverse field muon spectroscopy measurement rule out any possibility to have a nodal or anisotropic superconducting gap, revealing a conventional s-wave nature in the superconducting ground state. This work classifies A15 compound Ti$_{3}$X (X = Ir, Sb) as a time-reversal preserved topological superconductor.
A15化合物的拓扑非平凡带结构由于可能实现拓扑超导性而引起人们的关注。在这里，我们报告了用μ介子光谱测量对A15化合物Ti$ {3}$X (X = Ir, Sb)超导基态的微观研究。零场μ子测量表明，在这些材料中保持了时间反转对称性。此外，比热和横向场μ子光谱测量排除了存在节点或各向异性超导间隙的任何可能性，揭示了超导基态中的常规s波性质。本工作将A15化合物Ti$ {3}$X (X = Ir, Sb)归类为时间反转保存的拓扑超导体。
{"title":"Superconducting ground state of the topological superconducting candidates \u0000Ti3X\u0000 (\u0000X=Ir,Sb\u0000)","authors":"Manasi Mandal, K. P. Sajilesh, R. R. Chowdhury, D. Singh, P. Biswas, A. Hillier, R. P. Singh","doi":"10.1103/PHYSREVB.103.054501","DOIUrl":"https://doi.org/10.1103/PHYSREVB.103.054501","url":null,"abstract":"The topologically non-trivial band structure of A15 compounds has drawn attention owing to the possible realization of topological superconductivity. Here, we report a microscopic investigation of the superconducting ground state in A15 compound Ti$_{3}$X (X = Ir, Sb) by muon spectroscopy measurements. Zero field muon measurements have shown that time-reversal symmetry is preserved in these materials. Furthermore, specific heat and a transverse field muon spectroscopy measurement rule out any possibility to have a nodal or anisotropic superconducting gap, revealing a conventional s-wave nature in the superconducting ground state. This work classifies A15 compound Ti$_{3}$X (X = Ir, Sb) as a time-reversal preserved topological superconductor.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86918197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-11-02DOI: 10.1103/PHYSREVRESEARCH.3.023023
W. Atkinson, A. Kampf
We describe a mechanism by which the longitudinal thermal conductivity $kappa_{xx}$, measured in an in-plane magnetic field, oscillates as a function of field angle in layered nodal superconductors. These oscillations occur when the spin-orbit splitting at the nodes is larger than the nodal scattering rate, and are complementary to vortex-induced oscillations identified previously. In sufficiently anisotropic materials, the spin-orbit mechanism may be dominant. As a particular application, we focus on the cuprate high-temperature superconductor YBa$_2$Cu$_3$O$_{6+x}$. This material belongs to the class of Rashba bilayers, in which individual CuO$_2$ layers lack inversion symmetry although the crystal itself is globally centrosymmetric. We show that spin-orbit coupling endows $kappa_{xx}/T$ with a characteristic dependence on magnetic field angle that should be easily detected experimentally, and argue that for underdoped samples the spin-orbit contribution is larger than the vortex contribution. A key advantage of the magneto-thermal conductivity is that it is a bulk probe of spin-orbit physics, and therefore not sensitive to inversion breaking at surfaces.
{"title":"Intrinsic mechanism for magnetothermal conductivity oscillations in spin-orbit-coupled nodal superconductors","authors":"W. Atkinson, A. Kampf","doi":"10.1103/PHYSREVRESEARCH.3.023023","DOIUrl":"https://doi.org/10.1103/PHYSREVRESEARCH.3.023023","url":null,"abstract":"We describe a mechanism by which the longitudinal thermal conductivity $kappa_{xx}$, measured in an in-plane magnetic field, oscillates as a function of field angle in layered nodal superconductors. These oscillations occur when the spin-orbit splitting at the nodes is larger than the nodal scattering rate, and are complementary to vortex-induced oscillations identified previously. In sufficiently anisotropic materials, the spin-orbit mechanism may be dominant. As a particular application, we focus on the cuprate high-temperature superconductor YBa$_2$Cu$_3$O$_{6+x}$. This material belongs to the class of Rashba bilayers, in which individual CuO$_2$ layers lack inversion symmetry although the crystal itself is globally centrosymmetric. We show that spin-orbit coupling endows $kappa_{xx}/T$ with a characteristic dependence on magnetic field angle that should be easily detected experimentally, and argue that for underdoped samples the spin-orbit contribution is larger than the vortex contribution. A key advantage of the magneto-thermal conductivity is that it is a bulk probe of spin-orbit physics, and therefore not sensitive to inversion breaking at surfaces.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85774871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-29DOI: 10.1103/PhysRevB.103.L180504
Bo Fu, Zi-Ang Hu, Chang-An Li, Jian Li, S. Shen
Chiral Majorana hinge modes are characteristic of a second-order topological superconductor in three dimensions. Here we systematically study pairing symmetry in the point group D_{2h}, and find that the leading pairing channels can be of s-, d-, and s+id-wave pairing in Dirac materials. Except for the odd-parity s-wave pairing superconductivity, the s+id-wave pairing superconductor is topologically nontrivial and possesses Majorana hinge and surface modes. The chiral Majorana hinge modes can be characterized by a winding number of the quadrupole moment, or quantized quadruple moment at the symmetrically invariant point. Our findings suggest the strong spin-orbital coupling, crystalline symmetries and electron-electron interaction in the Dirac materials may provide a microscopic mechanism to realize chiral Majorana hinge modes without utilizing the proximity effect or external fields.
{"title":"Chiral Majorana Hinge Modes in Superconducting Dirac Materials","authors":"Bo Fu, Zi-Ang Hu, Chang-An Li, Jian Li, S. Shen","doi":"10.1103/PhysRevB.103.L180504","DOIUrl":"https://doi.org/10.1103/PhysRevB.103.L180504","url":null,"abstract":"Chiral Majorana hinge modes are characteristic of a second-order topological superconductor in three dimensions. Here we systematically study pairing symmetry in the point group D_{2h}, and find that the leading pairing channels can be of s-, d-, and s+id-wave pairing in Dirac materials. Except for the odd-parity s-wave pairing superconductivity, the s+id-wave pairing superconductor is topologically nontrivial and possesses Majorana hinge and surface modes. The chiral Majorana hinge modes can be characterized by a winding number of the quadrupole moment, or quantized quadruple moment at the symmetrically invariant point. Our findings suggest the strong spin-orbital coupling, crystalline symmetries and electron-electron interaction in the Dirac materials may provide a microscopic mechanism to realize chiral Majorana hinge modes without utilizing the proximity effect or external fields.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81343372","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-28DOI: 10.1103/PHYSREVMATERIALS.5.L021801
Cheng Huang, Jing Guo, K. Zhao, Fan Cui, Shengshan Qin, Q. Mu, Yazhou Zhou, Shu Cai, Chongli Yang, S. Long, Ke Yang, Aiguo Li, Qi Wu, Z. Ren, Jiangping Hu, Liling Sun
Here we report a pressure-induced reemergence of superconductivity in recently discovered superconductor K2Mo3As3, which is the first experimental case observed in quasi-one-dimensional superconductors. We find that, after full suppression of the ambient-pressure superconducting (SC-I) state at 8.7 GPa, an intermediary non-superconducting state sets in and prevails to the pressure up to 18.2 GPa, however, above this pressure a new superconducting (SC-II) state appears unexpectedly. High pressure x-ray diffraction measurements demonstrate that the pressure-induced dramatic change of the lattice parameter c contributes mainly to the emergence of the SC-II state. Combined with the theioretical calculations on band strcture, our results suggest that the reemergemce of superconductivity is associated with the change of the complicated interplay among different orbital electrons, driven by the pressure-induced unisotropic change of the lattice.
{"title":"Reemergence of superconductivity in pressurized quasi-one-dimensional superconductor \u0000K2Mo3As3","authors":"Cheng Huang, Jing Guo, K. Zhao, Fan Cui, Shengshan Qin, Q. Mu, Yazhou Zhou, Shu Cai, Chongli Yang, S. Long, Ke Yang, Aiguo Li, Qi Wu, Z. Ren, Jiangping Hu, Liling Sun","doi":"10.1103/PHYSREVMATERIALS.5.L021801","DOIUrl":"https://doi.org/10.1103/PHYSREVMATERIALS.5.L021801","url":null,"abstract":"Here we report a pressure-induced reemergence of superconductivity in recently discovered superconductor K2Mo3As3, which is the first experimental case observed in quasi-one-dimensional superconductors. We find that, after full suppression of the ambient-pressure superconducting (SC-I) state at 8.7 GPa, an intermediary non-superconducting state sets in and prevails to the pressure up to 18.2 GPa, however, above this pressure a new superconducting (SC-II) state appears unexpectedly. High pressure x-ray diffraction measurements demonstrate that the pressure-induced dramatic change of the lattice parameter c contributes mainly to the emergence of the SC-II state. Combined with the theioretical calculations on band strcture, our results suggest that the reemergemce of superconductivity is associated with the change of the complicated interplay among different orbital electrons, driven by the pressure-induced unisotropic change of the lattice.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81236916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-27DOI: 10.1103/physrevb.102.134511
D. Singh, M. Scheurer, A. Hillier, D. Adroja, R. Singh
Noncentrosymmetric superconductors have sparked significant research interests due to their exciting properties, such as the admixture of spin-singlet and spin-triplet Cooper pairs. Here we report $mu$SR and thermodynamic measurements on the noncentrosymmetric superconductor La7Rh3 which indicate a fully established superconducting gap and spontaneous time-reversal-symmetry breaking at the onset of superconductivity. We show that our results pose severe constraints on any microscopic theory of superconductivity in the system. A symmetry analysis identifies ground states compatible with time-reversal-symmetry breaking and the resulting gap functions are discussed. Furthermore, general energetic considerations indicate the relevance of electron-electron interactions for the pairing mechanism, in accordance with hints of spin-fluctuations revealed in susceptibility measurements.
{"title":"Time-reversal-symmetry breaking and unconventional pairing in the noncentrosymmetric superconductor \u0000La7Rh3","authors":"D. Singh, M. Scheurer, A. Hillier, D. Adroja, R. Singh","doi":"10.1103/physrevb.102.134511","DOIUrl":"https://doi.org/10.1103/physrevb.102.134511","url":null,"abstract":"Noncentrosymmetric superconductors have sparked significant research interests due to their exciting properties, such as the admixture of spin-singlet and spin-triplet Cooper pairs. Here we report $mu$SR and thermodynamic measurements on the noncentrosymmetric superconductor La7Rh3 which indicate a fully established superconducting gap and spontaneous time-reversal-symmetry breaking at the onset of superconductivity. We show that our results pose severe constraints on any microscopic theory of superconductivity in the system. A symmetry analysis identifies ground states compatible with time-reversal-symmetry breaking and the resulting gap functions are discussed. Furthermore, general energetic considerations indicate the relevance of electron-electron interactions for the pairing mechanism, in accordance with hints of spin-fluctuations revealed in susceptibility measurements.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88659059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Suyolcu, Jiaxin Sun, B. Goodge, Jisung Park, J. Schubert, L. Kourkoutis, D. Schlom
We demonstrate a-axis YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O7-x trilayers grown on (100) LaAlO3 substrates with improved interface smoothness. The trilayers are synthesized by ozone-assisted molecular-beam epitaxy. The thickness of the PrBa2Cu3O7-x layer is held constant at 8 nm and the thickness of the YBa2Cu3O7-x layers is varied from 24 nm to 100 nm. X-ray diffraction measurements show all trilayers to have >95% a-axis content. The rms roughness of the thinnest trilayer is < 0.7 nm and this roughness increases with the thickness of the YBa2Cu3O7-x layers. The thickness of the YBa2Cu3O7-x layers also affects the transport properties: while all samples exhibit an onset of the superconducting transition at and above 85 K, the thinner samples show wider transition widths, {Delta}Tc. High-resolution scanning transmission electron microscopy reveals coherent and chemically sharp interfaces, and that growth begins with a cubic (Y,Ba)CuO3-x perovskite phase that transforms into a-axis oriented YBa2Cu3O7-x as the substrate temperature is ramped up.
{"title":"a-axis YBa2Cu3O7−x/PrBa2Cu3O7−x/YBa2Cu3O7−x trilayers with subnanometer rms roughness","authors":"Y. Suyolcu, Jiaxin Sun, B. Goodge, Jisung Park, J. Schubert, L. Kourkoutis, D. Schlom","doi":"10.1063/5.0034648","DOIUrl":"https://doi.org/10.1063/5.0034648","url":null,"abstract":"We demonstrate a-axis YBa2Cu3O7-x/PrBa2Cu3O7-x/YBa2Cu3O7-x trilayers grown on (100) LaAlO3 substrates with improved interface smoothness. The trilayers are synthesized by ozone-assisted molecular-beam epitaxy. The thickness of the PrBa2Cu3O7-x layer is held constant at 8 nm and the thickness of the YBa2Cu3O7-x layers is varied from 24 nm to 100 nm. X-ray diffraction measurements show all trilayers to have >95% a-axis content. The rms roughness of the thinnest trilayer is < 0.7 nm and this roughness increases with the thickness of the YBa2Cu3O7-x layers. The thickness of the YBa2Cu3O7-x layers also affects the transport properties: while all samples exhibit an onset of the superconducting transition at and above 85 K, the thinner samples show wider transition widths, {Delta}Tc. High-resolution scanning transmission electron microscopy reveals coherent and chemically sharp interfaces, and that growth begins with a cubic (Y,Ba)CuO3-x perovskite phase that transforms into a-axis oriented YBa2Cu3O7-x as the substrate temperature is ramped up.","PeriodicalId":8514,"journal":{"name":"arXiv: Superconductivity","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90432367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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