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Moore RG, Lu Q, Jeon H, Yao X, Smith T, Pai YY, Chilcote M, Miao H, Okamoto S, Li AP, Oh S, Brahlek M. Monolayer Superconductivity and Tunable Topological Electronic Structure at the Fe(Te,Se)/Bi 2 Te 3 Interface. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2210940. [PMID: 36921318 DOI: 10.1002/adma.202210940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 03/07/2023] [Indexed: 06/02/2023]
Abstract
The interface between 2D topological Dirac states and an s-wave superconductor is expected to support Majorana-bound states (MBS) that can be used for quantum computing applications. Realizing these novel states of matter and their applications requires control over superconductivity and spin-orbit coupling to achieve spin-momentum-locked topological interface states (TIS) which are simultaneously superconducting. While signatures of MBS have been observed in the magnetic vortex cores of bulk FeTe0.55 Se0.45 , inhomogeneity and disorder from doping make these signatures unclear and inconsistent between vortices. Here superconductivity is reported in monolayer (ML) FeTe1-y Sey (Fe(Te,Se)) grown on Bi2 Te3 by molecular beam epitaxy (MBE). Spin and angle-resolved photoemission spectroscopy (SARPES) directly resolve the interfacial spin and electronic structure of Fe(Te,Se)/Bi2 Te3 heterostructures. For y = 0.25, the Fe(Te,Se) electronic structure is found to overlap with the Bi2 Te3 TIS and the desired spin-momentum locking is not observed. In contrast, for y = 0.1, reduced inhomogeneity measured by scanning tunneling microscopy (STM) and a smaller Fe(Te,Se) Fermi surface with clear spin-momentum locking in the topological states are found. Hence, it is demonstrated that the Fe(Te,Se)/Bi2 Te3 system is a highly tunable platform for realizing MBS where reduced doping can improve characteristics important for Majorana interrogation and potential applications.
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Affiliation(s)
- Robert G Moore
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Qiangsheng Lu
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Hoyeon Jeon
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Xiong Yao
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Tyler Smith
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Yun-Yi Pai
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Michael Chilcote
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Hu Miao
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Satoshi Okamoto
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - An-Ping Li
- Center for Nanophase Materials Science, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Seongshik Oh
- Department of Physics and Astronomy, Rutgers the State University of New Jersey, Piscataway, NJ, 08854, USA
| | - Matthew Brahlek
- Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
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Carva K, Vlaic P, Honolka J. Electronic Structure of Monolayer FeSe on Si(001) from First Principles. NANOMATERIALS (BASEL, SWITZERLAND) 2022; 12:270. [PMID: 35055287 PMCID: PMC8778465 DOI: 10.3390/nano12020270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 01/01/2022] [Accepted: 01/10/2022] [Indexed: 11/17/2022]
Abstract
The huge increase in the superconducting transition temperature of FeSe induced by an interface to SrTiO3 remains unexplained to date. However, there are numerous indications of the critical importance of specific features of the FeSe band topology in the vicinity of the Fermi surface. Here, we explore how the electronic structure of FeSe changes when located on another lattice matched substrate, namely a Si(001) surface, by first-principles calculations based on the density functional theory. We study non-magnetic (NM) and checkerboard anti-ferromagnetic (AFM) magnetic orders in FeSe and determine which interface arrangement is preferred. Our calculations reveal interesting effects of Si proximity on the FeSe band structure. Bands corresponding to hole pockets at the Γ point in NM FeSe are generally pushed down below the Fermi level, except for one band responsible for a small remaining hole pocket. Bands forming electron pockets centered at the M point of the Brillouin zone become less dispersive, and one of them is strongly hybridized with Si. We explain these changes by a redistribution of electrons between different Fe 3d orbitals rather than charge transfer to/from Si, and we also notice an associated loss of degeneracy between dxz and dyz orbitals.
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Affiliation(s)
- Karel Carva
- Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 12116 Prague 2, Czech Republic
| | - Petru Vlaic
- Molecular Sciences Department, University of Medicine and Pharmacy “Iuliu Hatieganu”, 400023 Cluj-Napoca, Romania;
| | - Jan Honolka
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 18221 Prague 8, Czech Republic;
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3
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Krzton-Maziopa A. Intercalated Iron Chalcogenides: Phase Separation Phenomena and Superconducting Properties. Front Chem 2021; 9:640361. [PMID: 34239856 PMCID: PMC8259132 DOI: 10.3389/fchem.2021.640361] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 04/07/2021] [Indexed: 11/15/2022] Open
Abstract
Organic molecule-intercalated layered iron-based monochalcogenides are presently the subject of intense research studies due to the linkage of their fascinating magnetic and superconducting properties to the chemical nature of guests present in the structure. Iron chalcogenides have the ability to host various organic species (i.e., solvates of alkali metals and the selected Lewis bases or long-chain alkylammonium cations) between the weakly bound inorganic layers, which opens up the possibility for fine tuning the magnetic and electrical properties of the intercalated phases by controlling both the doping level and the type/shape and orientation of the organic molecules. In recent years, significant progress has been made in the field of intercalation chemistry, expanding the gallery of intercalated superconductors with new hybrid inorganic–organic phases characterized by transition temperatures to a superconducting state as high as 46 K. A typical synthetic approach involves the low-temperature intercalation of layered precursors in the presence of liquid amines, and other methods, such as electrochemical intercalation, intercalant or ion exchange, and direct solvothermal growths from anhydrous amine-based media, are also being developed. Large organic guests, while entering a layered structure on intercalation, push off the inorganic slabs and modify the geometry of their internal building blocks (edge-sharing iron chalcogenide tetrahedrons) through chemical pressure. The chemical nature and orientation of organic molecules between the inorganic layers play an important role in structural modification and may serve as a tool for the alteration of the superconducting properties. A variety of donor species well-matched with the selected alkali metals enables the adjustment of electron doping in a host structure offering a broad range of new materials with tunable electric and magnetic properties. In this review, the main aspects of intercalation chemistry are discussed, involving the influence of the chemical and electrochemical nature of intercalating species on the crystal structure and critical issues related to the superconducting properties of the hybrid inorganic–organic phases. Mutual relations between the host and organic guests lead to a specific ordering of molecular species between the host layers, and their effect on the electronic structure of the host will be also argued. A brief description of a critical assessment of the association of the most effective chemical and electrochemical methods, which lead to the preparation of nanosized/microsized powders and single crystals of molecularly intercalated phases, with the ease of preparation of phase pure materials, crystal sizes, and the morphology of final products is given together with a discussion of the stability of the intercalated materials connected with the volatility of organic solvents and a possible degradation of host materials.
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Ewing S, Mazziotti DA. Correlation-driven phenomena in periodic molecular systems from variational two-electron reduced density matrix theory. J Chem Phys 2021; 154:214106. [PMID: 34240980 DOI: 10.1063/5.0050277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Correlation-driven phenomena in molecular periodic systems are challenging to predict computationally not only because such systems are periodically infinite but also because they are typically strongly correlated. Here, we generalize the variational two-electron reduced density matrix (2-RDM) theory to compute the energies and properties of strongly correlated periodic systems. The 2-RDM of the unit cell is directly computed subject to necessary N-representability conditions such that the unit-cell 2-RDM represents at least one N-electron density matrix. Two canonical but non-trivial systems, periodic metallic hydrogen chains and periodic acenes, are treated to demonstrate the methodology. We show that while single-reference correlation theories do not capture the strong (static) correlation effects in either of these molecular systems, the periodic variational 2-RDM theory predicts the Mott metal-to-insulator transition in the hydrogen chains and the length-dependent polyradical formation in acenes. For both hydrogen chains and acenes, the periodic calculations are compared with previous non-periodic calculations with the results showing a significant change in energies and increase in the electron correlation from the periodic boundary conditions. The 2-RDM theory, which allows for much larger active spaces than are traditionally possible, is applicable to studying correlation-driven phenomena in general periodic molecular solids and materials.
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Affiliation(s)
- Simon Ewing
- Department of Chemistry and The James Frank Institute, The University of Chicago, Chicago, Illinois 60637, USA
| | - David A Mazziotti
- Department of Chemistry and The James Frank Institute, The University of Chicago, Chicago, Illinois 60637, USA
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5
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Abstract
FeSe is classed as a Hund’s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund’s metals mostly originate from the exchange parameter J, which can drive a strong orbital selectivity in the correlations. The Fe-chalcogens are the most strongly correlated of the Fe-based superconductors, with dxy the most correlated orbital. Yet little is understood whether and how such correlations directly affect the superconducting instability in Hund’s systems. By applying a recently developed ab initio theory, we show explicitly the connections between correlations in dxy and the superconducting critical temperature Tc. Starting from the ab initio results as a reference, we consider various kinds of excursions in parameter space around the reference to determine what controls Tc. We show small excursions in J can cause colossal changes in Tc. Additionally we consider changes in hopping by varying the Fe-Se bond length in bulk, in the free standing monolayer M-FeSe, and M-FeSe on a SrTiO3 substrate (M-FeSe/STO). The twin conditions of proximity of the dxy state to the Fermi energy, and the strength of J emerge as the primary criteria for incoherent spectral response and enhanced single- and two-particle scattering that in turn controls Tc. Using c-RPA, we show further that FeSe in monolayer form (M-FeSe) provides a natural mechanism to enhance J. We explain why M-FeSe/STO has a high Tc, whereas M-FeSe in isolation should not. Our study opens a paradigm for a unified understanding what controls Tc in bulk, layers, and interfaces of Hund’s metals by hole pocket and electron screening cloud engineering.
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Koblischka MR, Slimani Y, Koblischka-Veneva A, Karwoth T, Zeng X, Hannachi E, Murakami M. Excess Conductivity Analysis of Polycrystalline FeSe Samples with the Addition of Ag. MATERIALS 2020; 13:ma13215018. [PMID: 33172199 PMCID: PMC7664390 DOI: 10.3390/ma13215018] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 10/31/2020] [Accepted: 11/03/2020] [Indexed: 11/20/2022]
Abstract
Bulk FeSe superconductors of the iron-based (IBS) “11” family containing various additions of silver were thoroughly investigated concerning the microstructure using optical microscopy and electron microscopy (TEM and SEM). The measurements of electrical resistivity were performed through the four-point technique in the temperature interval T= 2–150 K. The Aslamazov–Larkin model was employed to analyze the fluctuation-induced conductivity (FIC) in all acquired measurements. In all studied products, we found that the FIC curves consist of five different regimes of fluctuation, viz. critical region (CR), three-dimensional (3D), two-dimensional (2D), one-dimensional (1D), and shortwave fluctuation (SWF) regimes. The critical current density (Jc), the lower and upper critical magnetic fields (Bc1 and Bc2), the coherence length along the c-axis at zero-temperature (ξc(0)), and further parameters were assessed with regards to the silver amount within the products. The analyses discloses a diminution in the resistivity and a great reduction in ξc(0) with Ag addition. The optimal silver doping amount is achieved for 7 wt.%, which yields the best superconducting transition and the greatest Jc value.
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Affiliation(s)
- Michael Rudolf Koblischka
- Experimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, Germany; (A.K.-V.); (T.K.); (X.Z.)
- SIT Research Laboratories, Shibaura Institute of Technology, Tokyo 135-8548, Japan;
- Correspondence: or
| | - Yassine Slimani
- Department of Biophysics, Institute for Research and Medical Consultations (IRMC), Imam Abdulrahman Bin Faisal University, P.O. Box 1982, Dammam 31441, Saudi Arabia;
| | - Anjela Koblischka-Veneva
- Experimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, Germany; (A.K.-V.); (T.K.); (X.Z.)
- SIT Research Laboratories, Shibaura Institute of Technology, Tokyo 135-8548, Japan;
| | - Thomas Karwoth
- Experimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, Germany; (A.K.-V.); (T.K.); (X.Z.)
| | - XianLin Zeng
- Experimental Physics, Saarland University, P.O. Box 151150, D-66044 Saarbrücken, Germany; (A.K.-V.); (T.K.); (X.Z.)
| | - Essia Hannachi
- Laboratory of Physics of Materials—Structures and Properties, Department of Physics, Faculty of Sciences of Bizerte, University of Carthage, Zarzouna 7021, Tunisia;
| | - Masato Murakami
- SIT Research Laboratories, Shibaura Institute of Technology, Tokyo 135-8548, Japan;
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Abstract
Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.
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8
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Huh S, Song KH, Yang HJ, Jang SE, Kim K, Sur Y, Nam K, Kim KH, Hur NH. Solvothermal Synthesis and Interfacial Magnetic Interaction of β‐FeSe/SrTiO
3‐
x
Nanocomposites. ChemistrySelect 2020. [DOI: 10.1002/slct.202000871] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Seok Huh
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
| | - Kang Hyun Song
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
| | - Hee Jung Yang
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
| | - Si Eun Jang
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
| | - Kyungtae Kim
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
| | - Yeahan Sur
- Department of Physics and Astronomy Seoul National University Gwanak-gu Seoul 08826, Republic of Korea
| | - Kiwan Nam
- Department of Physics and Astronomy Seoul National University Gwanak-gu Seoul 08826, Republic of Korea
| | - Kee Hoon Kim
- Department of Physics and Astronomy Seoul National University Gwanak-gu Seoul 08826, Republic of Korea
| | - Nam Hwi Hur
- Department of Chemistry Sogang University Mapo-gu Seoul 04107, Republic of Korea
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9
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Song SY, Martiny JHJ, Kreisel A, Andersen BM, Seo J. Visualization of Local Magnetic Moments Emerging from Impurities in Hund's Metal States of FeSe. PHYSICAL REVIEW LETTERS 2020; 124:117001. [PMID: 32242691 DOI: 10.1103/physrevlett.124.117001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Revised: 09/30/2019] [Accepted: 02/21/2020] [Indexed: 06/11/2023]
Abstract
Understanding the origin of the magnetism of high temperature superconductors is crucial for establishing their unconventional pairing mechanism. Recently, theory predicts that FeSe is close to a magnetic quantum critical point, and thus weak perturbations such as impurities could induce local magnetic moments. To elucidate such quantum instability, we have employed scanning tunneling microscopy and spectroscopy. In particular, we have grown FeSe film on superconducting Pb(111) using molecular beam epitaxy and investigated magnetic excitation caused by impurities in the proximity-induced superconducting gap of FeSe. Our study provides deep insight into the origin of the magnetic ordering of FeSe by showing the way local magnetic moments develop in response to impurities near the magnetic quantum critical point.
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Affiliation(s)
- Sang Yong Song
- Department of Emerging Materials Science, DGIST, 333 Techno-Jungang-daero, Hyeonpung-Eup, Dalseong-Gun, Daegu 42988, Korea
| | - J H J Martiny
- Center for Nanostructured Graphene (CNG), Department of Physics, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | - A Kreisel
- Institut für Theoretische Physik, Universität Leipzig, D-04103 Leipzig, Germany
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Lyngbyvej 2, DK-2100 Copenhagen, Denmark
| | - Jungpil Seo
- Department of Emerging Materials Science, DGIST, 333 Techno-Jungang-daero, Hyeonpung-Eup, Dalseong-Gun, Daegu 42988, Korea
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10
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Choi YW, Choi HJ. Role of Electric Fields on Enhanced Electron Correlation in Surface-Doped FeSe. PHYSICAL REVIEW LETTERS 2019; 122:046401. [PMID: 30768316 DOI: 10.1103/physrevlett.122.046401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Indexed: 06/09/2023]
Abstract
Electron-doped high-T_{c} FeSe reportedly has a strong electron correlation that is enhanced with doping. It has been noticed that significant electric fields exist inevitably between FeSe and external donors along with electron transfer. However, the effects of such fields on the electron correlation are yet to be explored. Here we study potassium- (K-) dosed FeSe layers using density-functional theory combined with dynamical mean-field theory to investigate the roles of such electric fields on the strength of the electron correlation. We find, very interestingly, that the electronic potential-energy difference between the topmost Se and Fe atomic layers, generated by local electric fields of ionized K atoms, weakens the Se-mediated hopping between Fe d orbitals. Since it is the dominant hopping channel in FeSe, its reduction narrows the Fe d bands near the Fermi level, enhancing the electron correlation. This effect is orbital dependent and occurs in the topmost FeSe layer only. We also find the K dosing may increase the Se height, enhancing the electron correlation further. These results shed new light on the comprehensive study of high-T_{c} FeSe and other low-dimensional systems.
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Affiliation(s)
- Young Woo Choi
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
| | - Hyoung Joon Choi
- Department of Physics, Yonsei University, Seoul 03722, Republic of Korea
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11
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Reemergence of high-T c superconductivity in the (Li 1-xFe x )OHFe 1-ySe under high pressure. Nat Commun 2018; 9:380. [PMID: 29371605 PMCID: PMC5785538 DOI: 10.1038/s41467-018-02843-7] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/03/2018] [Indexed: 11/09/2022] Open
Abstract
In order to elucidate pressure-induced second superconducting phase (SC-II) in A x Fe2-ySe2 (A = K, Rb, Cs, and Tl) having an intrinsic phase separation, we perform a detailed high-pressure magnetotransport study on the isoelectronic, phase-pure (Li1-xFe x )OHFe1-ySe single crystals. Here we show that its ambient-pressure superconducting phase (SC-I) with a critical temperature Tc ≈ 40 K is suppressed gradually to below 2 K and an SC-II phase emerges above Pc ≈ 5 GPa with Tc increasing progressively to above 50 K up to 12.5 GPa. Our high-precision resistivity data uncover a sharp transition of the normal state from Fermi liquid for SC-I to non-Fermi liquid for SC-II phase. In addition, the reemergence of high-Tc SC-II is found to accompany with a concurrent enhancement of electron carrier density. Without structural transition below 10 GPa, the observed SC-II with enhanced carrier density should be ascribed to an electronic origin presumably associated with pressure-induced Fermi surface reconstruction.
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12
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Duong DL, Yun SJ, Lee YH. van der Waals Layered Materials: Opportunities and Challenges. ACS NANO 2017; 11:11803-11830. [PMID: 29219304 DOI: 10.1021/acsnano.7b07436] [Citation(s) in RCA: 148] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Since graphene became available by a scotch tape technique, a vast class of two-dimensional (2D) van der Waals (vdW) layered materials has been researched intensively. What is more intriguing is that the well-known physics and chemistry of three-dimensional (3D) bulk materials are often irrelevant, revealing exotic phenomena in 2D vdW materials. By further constructing heterostructures of these materials in the planar and vertical directions, which can be easily achieved via simple exfoliation techniques, numerous quantum mechanical devices have been demonstrated for fundamental research and technological applications. It is, therefore, necessary to review the special features in 2D vdW materials and to discuss the remaining issues and challenges. Here, we review the vdW materials library, technology relevance, and specialties of vdW materials covering the vdW interaction, strong Coulomb interaction, layer dependence, dielectric screening engineering, work function modulation, phase engineering, heterostructures, stability, growth issues, and the remaining challenges.
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Affiliation(s)
- Dinh Loc Duong
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Seok Joon Yun
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
| | - Young Hee Lee
- Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea
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13
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Sun JP, Ye GZ, Shahi P, Yan JQ, Matsuura K, Kontani H, Zhang GM, Zhou Q, Sales BC, Shibauchi T, Uwatoko Y, Singh DJ, Cheng JG. High-T_{c} Superconductivity in FeSe at High Pressure: Dominant Hole Carriers and Enhanced Spin Fluctuations. PHYSICAL REVIEW LETTERS 2017; 118:147004. [PMID: 28430492 DOI: 10.1103/physrevlett.118.147004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Indexed: 06/07/2023]
Abstract
The importance of electron-hole interband interactions is widely acknowledged for iron-pnictide superconductors with high transition temperatures (T_{c}). However, the absence of hole pockets near the Fermi level of the iron-selenide (FeSe) derived high-T_{c} superconductors raises a fundamental question of whether iron pnictides and chalcogenides have different pairing mechanisms. Here, we study the properties of electronic structure in the high-T_{c} phase induced by pressure in bulk FeSe from magnetotransport measurements and first-principles calculations. With increasing pressure, the low-T_{c} superconducting phase transforms into the high-T_{c} phase, where we find the normal-state Hall resistivity changes sign from negative to positive, demonstrating dominant hole carriers in contrast to other FeSe-derived high-T_{c} systems. Moreover, the Hall coefficient is enlarged and the magnetoresistance exhibits anomalous scaling behaviors, evidencing strongly enhanced interband spin fluctuations in the high-T_{c} phase. These results in FeSe highlight similarities with high-T_{c} phases of iron pnictides, constituting a step toward a unified understanding of iron-based superconductivity.
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Affiliation(s)
- J P Sun
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - G Z Ye
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Science and Astronomy, Yunnan University, Kunming 650091, China
| | - P Shahi
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - J-Q Yan
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - K Matsuura
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - H Kontani
- Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan
| | - G M Zhang
- State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
| | - Q Zhou
- School of Physical Science and Astronomy, Yunnan University, Kunming 650091, China
| | - B C Sales
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Y Uwatoko
- The Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - D J Singh
- Department of Physics and Astronomy, University of Missouri, Columbia, Missouri 65211-7010, USA
| | - J-G Cheng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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14
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Ptok A, Kapcia KJ, Cichy A, Oleś AM, Piekarz P. Magnetic Lifshitz transition and its consequences in multi-band iron-based superconductors. Sci Rep 2017; 7:41979. [PMID: 28165043 PMCID: PMC5292748 DOI: 10.1038/srep41979] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Accepted: 01/04/2017] [Indexed: 11/09/2022] Open
Abstract
In this paper we address Lifshitz transition induced by applied external magnetic field in a case of iron-based superconductors, in which a difference between the Fermi level and the edges of the bands is relatively small. We introduce and investigate a two-band model with intra-band pairing in the relevant parameters regime to address a generic behaviour of a system with hole-like and electron-like bands in external magnetic field. Our results show that two Lifshitz transitions can develop in analysed systems and the first one occurs in the superconducting phase and takes place at approximately constant magnetic field. The chosen sets of the model parameters can describe characteristic band structure of iron-based superconductors and thus the obtained results can explain the experimental observations in FeSe and Co-doped BaFe2As2 compounds.
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Affiliation(s)
- Andrzej Ptok
- Institute of Physics, Maria Curie-Skłodowska University, Plac M. Skłodowskiej-Curie 1, PL-20031 Lublin, Poland.,Institute of Nuclear Physics, Polish Academy of Sciences, ul. E. Radzikowskiego 152, PL-31342 Kraków, Poland
| | - Konrad J Kapcia
- Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668 Warsaw, Poland
| | - Agnieszka Cichy
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, D-55099 Mainz, Germany
| | - Andrzej M Oleś
- Marian Smoluchowski Institute of Physics, Jagiellonian University, ul. prof. S. Łojasiewicza 11, PL-30348 Kraków, Poland.,Max Planck Institute for Solid State Research, Heisenbergstrasse 1, D-70569 Stuttgart, Germany
| | - Przemysław Piekarz
- Institute of Nuclear Physics, Polish Academy of Sciences, ul. E. Radzikowskiego 152, PL-31342 Kraków, Poland
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15
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Mishra V, Scalapino DJ, Maier TA. s± pairing near a Lifshitz transition. Sci Rep 2016; 6:32078. [PMID: 27561327 PMCID: PMC4999992 DOI: 10.1038/srep32078] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 08/02/2016] [Indexed: 11/09/2022] Open
Abstract
Observations of robust superconductivity in some of the iron based superconductors in the vicinity of a Lifshitz point where a spin density wave instability is suppressed as the hole band drops below the Fermi energy raise questions for spin-fluctuation theories. Here we discuss spin-fluctuation pairing for a bilayer Hubbard model, which goes through such a Lifshitz transition. We find s± pairing with a transition temperature that peaks beyond the Lifshitz point and a gap function that has essentially the same magnitude but opposite sign on the incipient hole band as it does on the electron band that has a Fermi surface.
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Affiliation(s)
- Vivek Mishra
- Joint Institute of Computational Sciences, University of Tennessee, Knoxville, TN-37996, USA
| | - Douglas J Scalapino
- Department of Physics, University of California, Santa Barbara, CA-93106, USA
| | - Thomas A Maier
- Computer Science and Mathematics Division &Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN-37831, USA
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16
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Linscheid A, Maiti S, Wang Y, Johnston S, Hirschfeld PJ. High T_{c} via Spin Fluctuations from Incipient Bands: Application to Monolayers and Intercalates of FeSe. PHYSICAL REVIEW LETTERS 2016; 117:077003. [PMID: 27563992 DOI: 10.1103/physrevlett.117.077003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2016] [Indexed: 06/06/2023]
Abstract
We investigate superconductivity in a two-band system with an electronlike and a holelike band, where one of the bands is away from the Fermi level (or "incipient"). We argue that the incipient band contributes significantly to spin-fluctuation pairing in the strong coupling limit where the system is close to a magnetic instability and can lead to a large T_{c}. In this case, T_{c} is limited by a competition between the frequency range of the coupling (set by an isolated paramagnon) and the coupling strength itself, such that a domelike T_{c} dependence on the incipient band position is obtained. The coupling of electrons to phonons is found to further enhance T_{c}. The results are discussed in the context of experiments on monolayers and intercalates of FeSe.
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Affiliation(s)
- A Linscheid
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - S Maiti
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
| | - Y Wang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - S Johnston
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, Florida 32611, USA
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17
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Lei B, Cui JH, Xiang ZJ, Shang C, Wang NZ, Ye GJ, Luo XG, Wu T, Sun Z, Chen XH. Evolution of High-Temperature Superconductivity from a Low-T_{c} Phase Tuned by Carrier Concentration in FeSe Thin Flakes. PHYSICAL REVIEW LETTERS 2016; 116:077002. [PMID: 26943553 DOI: 10.1103/physrevlett.116.077002] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Indexed: 05/05/2023]
Abstract
We report the evolution of superconductivity in an FeSe thin flake with systematically regulated carrier concentrations by the liquid-gating technique. With electron doping tuned by the gate voltage, high-temperature superconductivity with an onset at 48 K can be achieved in an FeSe thin flake with T_{c} less than 10 K. This is the first time such high temperature superconductivity in FeSe is achieved without either an epitaxial interface or external pressure, and it definitely proves that the simple electron-doping process is able to induce high-temperature superconductivity with T_{c}^{onset} as high as 48 K in bulk FeSe. Intriguingly, our data also indicate that the superconductivity is suddenly changed from a low-T_{c} phase to a high-T_{c} phase with a Lifshitz transition at a certain carrier concentration. These results help to build a unified picture to understand the high-temperature superconductivity among all FeSe-derived superconductors and shed light on the further pursuit of a higher T_{c} in these materials.
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Affiliation(s)
- B Lei
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - J H Cui
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Z J Xiang
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - C Shang
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - N Z Wang
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - G J Ye
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
| | - X G Luo
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - T Wu
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Z Sun
- National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - X H Chen
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, and Key Laboratory of Strongly-coupled Quantum Matter Physics, Chinese Academy of Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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18
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Common electronic origin of superconductivity in (Li,Fe)OHFeSe bulk superconductor and single-layer FeSe/SrTiO3 films. Nat Commun 2016; 7:10608. [PMID: 26853801 PMCID: PMC4748121 DOI: 10.1038/ncomms10608] [Citation(s) in RCA: 148] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Accepted: 01/04/2016] [Indexed: 11/09/2022] Open
Abstract
The mechanism of high-temperature superconductivity in the iron-based superconductors remains an outstanding issue in condensed matter physics. The electronic structure plays an essential role in dictating superconductivity. Recent revelation of distinct electronic structure and high-temperature superconductivity in the single-layer FeSe/SrTiO3 films provides key information on the role of Fermi surface topology and interface in inducing or enhancing superconductivity. Here we report high-resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of an FeSe-based superconductor, (Li0.84Fe0.16)OHFe0.98Se, with a Tc at 41 K. We find that this single-phase bulk superconductor shows remarkably similar electronic behaviours to that of the superconducting single-layer FeSe/SrTiO3 films in terms of Fermi surface topology, band structure and the gap symmetry. These observations provide new insights in understanding high-temperature superconductivity in the single-layer FeSe/SrTiO3 films and the mechanism of superconductivity in the bulk iron-based superconductors.
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