1
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Zhou YZ, Chen J, Li ZX, Luo J, Yang J, Guo YF, Wang WH, Zhou R, Zheng GQ. Antiferromagnetic Spin Fluctuations and Unconventional Superconductivity in Topological Superconductor Candidate YPtBi Revealed by ^{195}Pt-NMR. PHYSICAL REVIEW LETTERS 2023; 130:266002. [PMID: 37450816 DOI: 10.1103/physrevlett.130.266002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 03/22/2023] [Accepted: 05/16/2023] [Indexed: 07/18/2023]
Abstract
We report ^{195}Pt nuclear magnetic resonance (NMR) measurements on topological superconductor candidate YPtBi, which has broken inversion symmetry and topological nontrivial band structures due to the strong spin-orbit coupling. In the normal state, we find that Knight shift K is field- and temperature independent, suggesting that the contribution from the topological bands is very small at low temperatures. However, the spin-lattice relaxation rate 1/T_{1} divided by temperature (T), 1/T_{1}T, increases with decreasing T, implying the existence of antiferromagnetic spin fluctuations. In the superconducting state, no Hebel-Slichter coherence peak is seen below T_{c} and 1/T_{1} follows T^{3} variation, indicating the unconventional superconductivity. The finite spin susceptibility at zero-temperature limit and the anomalous increase of the NMR linewidth below T_{c} point to a mixed state of spin-singlet and spin-triplet (or spin-septet) pairing.
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Affiliation(s)
- Y Z Zhou
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - J Chen
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - Z X Li
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - J Luo
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - J Yang
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - Y F Guo
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
- ShanghaiTech Laboratory for Topological Physics, Shanghai 201210, China
| | - W H Wang
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
| | - R Zhou
- Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Guo-Qing Zheng
- Department of Physics, Okayama University, Okayama 700-8530, Japan
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2
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Quintero MA, Shen J, Laing CC, Wolverton C, Kanatzidis MG. Cubic Stuffed-Diamond Semiconductors LiCu 3TiQ 4 (Q = S, Se, and Te). J Am Chem Soc 2022; 144:12789-12799. [PMID: 35797169 DOI: 10.1021/jacs.2c03501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Lithium chalcogenides have been understudied, owing to the difficulty in managing the chemical reactivity of lithium. These materials are of interest as potential ion conductors and thermal neutron detectors. In this study, we describe three new cubic lithium copper chalcotitanates that crystallize in the P4̅3m space group. LiCu3TiS4, a = 5.5064(6) Å, and LiCu3TiSe4, a = 5.7122(7) Å, represent two members of a new stuffed diamond-type crystal structure, while LiCu3TiTe4, a = 5.9830(7) Å crystallized into a similar structure exhibiting lithium and copper mixed occupancy. These structures can be understood as hybrids of the zinc-blende and sulvanite structure types. In situ powder X-ray diffraction was utilized to construct a "panoramic" reaction map for the preparation of LiCu3TiTe4, facilitating the design of a rational synthesis and uncovering three new transient phases. LiCu3TiS4 and LiCu3TiSe4 are thermally stable up to 1000 °C under vacuum, while LiCu3TiTe4 partially decomposes when slowly cooled to 400 °C. Density functional theory calculations suggest that these compounds are indirect band gap semiconductors. The measured work functions are 4.77(5), 4.56(5), and 4.69(5) eV, and the measured band gaps are 2.23(5), 1.86(5), and 1.34(5) eV for the S, Se, and Te analogues, respectively.
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Affiliation(s)
- Michael A Quintero
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Jiahong Shen
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Craig C Laing
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Christopher Wolverton
- Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States
| | - Mercouri G Kanatzidis
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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3
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Samatham SS, Patel A, Mishra AK, Lukoyanov AV, Gramateeva LN, Lakhani A, Vedachalaiyer G, Gopinatha Warrier SK. Experimental and Theoretical Investigations of Fe-Doped Hexagonal MnNiGe. ACS OMEGA 2022; 7:18110-18121. [PMID: 35664626 PMCID: PMC9161421 DOI: 10.1021/acsomega.2c01571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/19/2022] [Accepted: 05/05/2022] [Indexed: 06/15/2023]
Abstract
We report a comprehensive investigation of MnNi0.7Fe0.3Ge Heusler alloy to explore its magnetic, caloric, and electrical transport properties. The alloy undergoes a ferromagnetic transition across T C ∼ 212 K and a weak-antiferromagnetic transition across T t ∼ 180 K followed by a spin-glass transition below T f ∼ 51.85 K. A second-order phase transition across T C with mixed short and long-range magnetic interactions is confirmed through the critical exponent study and universal scaling of magnetic entropy and magnetoresistance. A weak first-order phase transition is evident across T t from magnetization and specific heat data. The frequency dependent cusp in χAC(T) along with the absence of a clear magnetic transition in specific heat C(T) and resistivity ρ(T) establish the spin glass behavior below T f. Mixed ferromagnetic and antiferromagnetic interactions with dominant ferromagnetic coupling, as revealed by density functional calculations, are experimentally evident from the large positive Weiss temperature, magnetic saturation, and negative magnetic-entropy and magnetoresistance.
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Affiliation(s)
- S. Shanmukharao Samatham
- Department
of Physics, Chaitanya Bharathi Institute
of Technology, Gandipet, Hyderabad 500075, India
| | - Akhilesh
Kumar Patel
- Magnetic
Materials Laboratory, Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400 076, India
| | - Ashish Kumar Mishra
- UGC-DAE
Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, Madhya
Pradesh, India
| | - Alexey V. Lukoyanov
- M.
N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy
of Sciences, 620108 Ekaterinburg, Russia
- Ural
Federal University, 620002 Ekaterinburg, Russia
| | - Lyubov N. Gramateeva
- M.
N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy
of Sciences, 620108 Ekaterinburg, Russia
| | - Archana Lakhani
- UGC-DAE
Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, Madhya
Pradesh, India
| | - Ganesan Vedachalaiyer
- UGC-DAE
Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001, Madhya
Pradesh, India
- Medi-Caps
University, A.B. Road,
Pigdamber, Rau, Indore 453331, Madhya Pradesh, India
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4
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Kore A, Ara N, Singh P. First principle based investigation of topological insulating phase in half-Heusler family Na YO ( Y= Ag, Au, and Cu). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:205501. [PMID: 35196267 DOI: 10.1088/1361-648x/ac57d7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Accepted: 02/23/2022] [Indexed: 06/14/2023]
Abstract
The ternary half-Heusler compounds have shown great potential for realizing new 3D topological insulators. With band gap tuning and spin orbit coupling these compounds may undergo topological phase transitions. In present work, we explore the possibility of realizing a topological insulating phase in half-Heusler family NaYO (Y= Ag, Au, and Cu). We find that for NaAgO, external strain (∼19%) along with spin-orbit coupling (SOC), is required to achieve band-inversion at Γ high-symmetry point and leads to phase transition from trivial to non-trivial topological insulating phase. In case of NaAuO and NaCuO, non-trivial phase appears in their equilibrium lattice constant, hence only SOC is enough to achieve band-inversion leading to non-trivial topology. The non-centrosymmetric nature of crystal geometry leads to the formation of two twofold degenerate point nodes near the Fermi level.
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Affiliation(s)
- Ashish Kore
- Department of Physics, Visvesvaraya National Institute of Technology, Nagpur-10 India
| | - Nisa Ara
- Department of Physics, Visvesvaraya National Institute of Technology, Nagpur-10 India
| | - Poorva Singh
- Department of Physics, Visvesvaraya National Institute of Technology, Nagpur-10 India
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5
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Efficient spin current source using a half-Heusler alloy topological semimetal with back end of line compatibility. Sci Rep 2022; 12:2426. [PMID: 35165335 PMCID: PMC8844406 DOI: 10.1038/s41598-022-06325-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Accepted: 01/27/2022] [Indexed: 11/16/2022] Open
Abstract
Topological materials, such as topological insulators (TIs), have great potential for ultralow power spintronic devices, thanks to their giant spin Hall effect. However, the giant spin Hall angle (θSH > 1) is limited to a few chalcogenide TIs with toxic elements and low melting points, making them challenging for device integration during the silicon Back-End-of-Line (BEOL) process. Here, we show that by using a half-Heusler alloy topological semi-metal (HHA-TSM), YPtBi, it is possible to achieve both a giant θSH up to 4.1 and a high thermal budget up to 600 °C. We demonstrate magnetization switching of a CoPt thin film using the giant spin Hall effect of YPtBi by current densities lower than those of heavy metals by one order of magnitude. Since HHA-TSM includes a group of three-element topological materials with great flexibility, our work opens the door to the third-generation spin Hall materials with both high θSH and high compatibility with the BEOL process that would be easily adopted by the industry.
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6
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Kang X, Kang L, Chen W, Deng X. A generative approach to modeling data with quantitative and qualitative responses. J MULTIVARIATE ANAL 2022. [DOI: 10.1016/j.jmva.2022.104952] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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7
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Gui X, Feng E, Cao H, Cava RJ. Ferromagnetic Cr 4PtGa 17: A Half-Heusler-Type Compound with a Breathing Pyrochlore Lattice. J Am Chem Soc 2021; 143:14342-14351. [PMID: 34449205 DOI: 10.1021/jacs.1c06667] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe the crystal structure and elementary magnetic properties of a previously unreported ternary intermetallic compound, Cr4PtGa17, which crystallizes in a rhombohedral unit cell in the noncentrosymmetric space group R3m. The crystal structure is closely related to those of XYZ half-Heusler compounds, where X, Y, and Z are reported to be single elements only, occupying three different face-centered-cubic sublattices. The new material, Cr4PtGa17, can be most straightforwardly illustrated by writing the formula as (PtGa2)(Cr4Ga14)Ga (X = PtGa2, Y = Cr4Ga14, Z = Ga); that is, the X and Y sites are occupied by clusters instead of single elements. The magnetic Cr occupies a breathing pyrochlore lattice. Ferromagnetic ordering is found below TC ∼ 61 K, by both neutron diffraction and magnetometer studies, with a small, saturated moment of ∼0.25 μB/Cr observed at 2 K, making Cr4PtGa17 the first ferromagnetically ordered material with a breathing pyrochlore lattice. A magnetoresistance of ∼140% was observed at 2 K. DFT calculations suggest that the material has a nearly half-metallic electronic structure. The new material, Cr4PtGa17, the first realization of both a half-Heusler-type structure and a breathing pyrochlore lattice, might pave a new way to achieve novel types of half-Heusler compounds.
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Affiliation(s)
- Xin Gui
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States
| | - Erxi Feng
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Huibo Cao
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert J Cava
- Department of Chemistry, Princeton University, Princeton, New Jersey 08540, United States
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8
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Du D, Manzo S, Zhang C, Saraswat V, Genser KT, Rabe KM, Voyles PM, Arnold MS, Kawasaki JK. Epitaxy, exfoliation, and strain-induced magnetism in rippled Heusler membranes. Nat Commun 2021; 12:2494. [PMID: 33941781 PMCID: PMC8093223 DOI: 10.1038/s41467-021-22784-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 03/29/2021] [Indexed: 11/09/2022] Open
Abstract
Single-crystalline membranes of functional materials enable the tuning of properties via extreme strain states; however, conventional routes for producing membranes require the use of sacrificial layers and chemical etchants, which can both damage the membrane and limit the ability to make them ultrathin. Here we demonstrate the epitaxial growth of the cubic Heusler compound GdPtSb on graphene-terminated Al2O3 substrates. Despite the presence of the graphene interlayer, the Heusler films have epitaxial registry to the underlying sapphire, as revealed by x-ray diffraction, reflection high energy electron diffraction, and transmission electron microscopy. The weak Van der Waals interactions of graphene enable mechanical exfoliation to yield free-standing GdPtSb membranes, which form ripples when transferred to a flexible polymer handle. Whereas unstrained GdPtSb is antiferromagnetic, measurements on rippled membranes show a spontaneous magnetic moment at room temperature, with a saturation magnetization of 5.2 bohr magneton per Gd. First-principles calculations show that the coupling to homogeneous strain is too small to induce ferromagnetism, suggesting a dominant role for strain gradients. Our membranes provide a novel platform for tuning the magnetic properties of intermetallic compounds via strain (piezomagnetism and magnetostriction) and strain gradients (flexomagnetism).
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Affiliation(s)
- Dongxue Du
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Sebastian Manzo
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Chenyu Zhang
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Vivek Saraswat
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Konrad T Genser
- Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA
| | - Karin M Rabe
- Department of Physics and Astronomy, Rutgers University, New Brunswick, NJ, USA
| | - Paul M Voyles
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Michael S Arnold
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Jason K Kawasaki
- Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.
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9
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Bhardwaj V, Bhattacharya A, Srivastava S, Khovaylo VV, Sannigrahi J, Banerjee N, Mani BK, Chatterjee R. Strain driven emergence of topological non-triviality in YPdBi thin films. Sci Rep 2021; 11:7535. [PMID: 33824352 PMCID: PMC8024271 DOI: 10.1038/s41598-021-86936-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Accepted: 03/22/2021] [Indexed: 02/01/2023] Open
Abstract
Half-Heusler compounds exhibit a remarkable variety of emergent properties such as heavy-fermion behaviour, unconventional superconductivity and magnetism. Several of these compounds have been predicted to host topologically non-trivial electronic structures. Remarkably, recent theoretical studies have indicated the possibility to induce non-trivial topological surface states in an otherwise trivial half-Heusler system by strain engineering. Here, using magneto-transport measurements and first principles DFT-based simulations, we demonstrate topological surface states on strained [110] oriented thin films of YPdBi grown on (100) MgO. These topological surface states arise in an otherwise trivial semi-metal purely driven by strain. Furthermore, we observe the onset of superconductivity in these strained films highlighting the possibility of engineering a topological superconducting state. Our results demonstrate the critical role played by strain in engineering novel topological states in thin film systems for developing next-generation spintronic devices.
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Affiliation(s)
- Vishal Bhardwaj
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Anupam Bhattacharya
- Department of Mechanical Engineering, Indian Institute of Technology Delhi, New Delhi, India
| | - Shivangi Srivastava
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
| | - Vladimir V Khovaylo
- National University of Science and Technology "MISiS", Moscow, Russia, 119049
| | - Jhuma Sannigrahi
- Department of Physics, Loughborough University, Loughborough, LE11 3TU, UK
| | - Niladri Banerjee
- Department of Physics, Loughborough University, Loughborough, LE11 3TU, UK.
| | - Brajesh K Mani
- Department of Physics, Indian Institute of Technology Delhi, New Delhi, India
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10
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Elphick K, Frost W, Samiepour M, Kubota T, Takanashi K, Sukegawa H, Mitani S, Hirohata A. Heusler alloys for spintronic devices: review on recent development and future perspectives. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2021; 22:235-271. [PMID: 33828415 PMCID: PMC8009123 DOI: 10.1080/14686996.2020.1812364] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2020] [Revised: 08/17/2020] [Accepted: 08/17/2020] [Indexed: 05/14/2023]
Abstract
Heusler alloys are theoretically predicted to become half-metals at room temperature (RT). The advantages of using these alloys are good lattice matching with major substrates, high Curie temperature above RT and intermetallic controllability for spin density of states at the Fermi energy level. The alloys are categorised into half- and full-Heusler alloys depending upon the crystalline structures, each being discussed both experimentally and theoretically. Fundamental properties of ferromagnetic Heusler alloys are described. Both structural and magnetic characterisations on an atomic scale are typically carried out in order to prove the half-metallicity at RT. Atomic ordering in the films is directly observed by X-ray diffraction and is also indirectly probed via the temperature dependence of electrical resistivity. Element specific magnetic moments and spin polarisation of the Heusler alloy films are directly measured using X-ray magnetic circular dichroism and Andreev reflection, respectively. By employing these ferromagnetic alloy films in a spintronic device, efficient spin injection into a non-magnetic material and large magnetoresistance are also discussed. Fundamental properties of antiferromagnetic Heusler alloys are then described. Both structural and magnetic characterisations on an atomic scale are shown. Atomic ordering in the Heusler alloy films is indirectly measured by the temperature dependence of electrical resistivity. Antiferromagnetic configurations are directly imaged by X-ray magnetic linear dichroism and polarised neutron reflection. The applications of the antiferromagnetic Heusler alloy films are also explained. The other non-magnetic Heusler alloys are listed. A brief summary is provided at the end of this review.
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Affiliation(s)
- Kelvin Elphick
- Department of Electronic Engineering, University of York, York, UK
| | - William Frost
- Department of Electronic Engineering, University of York, York, UK
| | - Marjan Samiepour
- Department of Electronic Engineering, University of York, York, UK
- Seagate Technology,1 Disc Drive, Springtown Industrial Estate, Londonderry, Northern Ireland
| | - Takahide Kubota
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, Japan
| | - Koki Takanashi
- Institute for Materials Research, Tohoku University, Sendai, Japan
- Center for Spintronics Research Network, Tohoku University, Sendai, Japan
- Center for Science and Innovation in Spintronics, Core Research Cluster, Tohoku University, Sendai, Japan
| | - Hiroaki Sukegawa
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan
| | - Seiji Mitani
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science, Tsukuba, Japan
- Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Japan
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11
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Kumar N, Guin SN, Manna K, Shekhar C, Felser C. Topological Quantum Materials from the Viewpoint of Chemistry. Chem Rev 2021; 121:2780-2815. [PMID: 33151662 PMCID: PMC7953380 DOI: 10.1021/acs.chemrev.0c00732] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Indexed: 11/29/2022]
Abstract
Topology, a mathematical concept, has recently become a popular and truly transdisciplinary topic encompassing condensed matter physics, solid state chemistry, and materials science. Since there is a direct connection between real space, namely atoms, valence electrons, bonds, and orbitals, and reciprocal space, namely bands and Fermi surfaces, via symmetry and topology, classifying topological materials within a single-particle picture is possible. Currently, most materials are classified as trivial insulators, semimetals, and metals or as topological insulators, Dirac and Weyl nodal-line semimetals, and topological metals. The key ingredients for topology are certain symmetries, the inert pair effect of the outer electrons leading to inversion of the conduction and valence bands, and spin-orbit coupling. This review presents the topological concepts related to solids from the viewpoint of a solid-state chemist, summarizes techniques for growing single crystals, and describes basic physical property measurement techniques to characterize topological materials beyond their structure and provide examples of such materials. Finally, a brief outlook on the impact of topology in other areas of chemistry is provided at the end of the article.
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Affiliation(s)
- Nitesh Kumar
- Max Planck Institute for
Chemical
Physics of Solids, 01187 Dresden, Germany
| | - Satya N. Guin
- Max Planck Institute for
Chemical
Physics of Solids, 01187 Dresden, Germany
| | - Kaustuv Manna
- Max Planck Institute for
Chemical
Physics of Solids, 01187 Dresden, Germany
| | - Chandra Shekhar
- Max Planck Institute for
Chemical
Physics of Solids, 01187 Dresden, Germany
| | - Claudia Felser
- Max Planck Institute for
Chemical
Physics of Solids, 01187 Dresden, Germany
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12
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Zhang J, Ding F, Lee JJ, Shan G, Bobev S. One Structure, Two Elements-LuGe 2 Superconductor vs Ordinary Metallic Conductor LuSn 2. A Case Study on How Site-Selective Germanium for Tin Atom Substitution Leads to Modulating of the Charge Distribution. Inorg Chem 2020; 59:16853-16864. [PMID: 32970413 DOI: 10.1021/acs.inorgchem.0c01062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The substitution of chemically similar elements in a given crystal structure is an effective way to enhance physical properties, but the understanding on such improvements is usually impeded because the substitutions are random, and the roles of the different atoms cannot be distinguished by crystallographic symmetry. Herein, we provide a detailed crystallographic analysis and property measurements for the continuous solid solutions LuGexSn2-x (0 < x < 2). The results show that there is no apparent change of the global symmetry, with the end-members LuGe2 and LuSn2, as well as the intermediate LuGexSn2-x compositions adopting the ZrSi2 type structure (space group Cmcm, Pearson index oC12). Yet, the refinements of the crystal structures from single-crystal X-ray diffraction data show that Ge-Sn atom substitutions are not random, but occur preferentially at the zigzag chain. The patterned distribution of two group 14 elements leads to a significant variation in chemical bonding and charge ordering within the other structural fragment, the 2D square nets, thereby resulting in tuned electron transport. The enhancement is greater than that for the typical Bloch-Gruneisen model and more akin to that for the parallel-resistor model. Magnetization measurements on single crystals show bulk superconductivity in all LuGexSn2-x samples with shielding fractions as high as 90%. Specific heat data confirm the effect to originate from residual metallic tin in the material, indicating that Sn atom substitutions in the 2D square nets cause disruptions of the hypervalent bonding and local anisotropy, which ultimately leads to vanishing of the superconducting state in the end-member LuGe2. This work sheds light on how the complexity in chemical interactions by two different carbon congeners leads to changes in the physical properties and how they can be correlated with the induced charge distribution. These studies also provide a general approach to modulation of charge density and. thus, of emerging physical properties in other classes of intermetallic systems based on the main-group elements of groups 13 to 15.
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Affiliation(s)
- Jiliang Zhang
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States.,Department of Materials Science and Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Fazhu Ding
- Key Laboratory of Applied Superconductivity and Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.,University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Jey-Jau Lee
- National Synchrotron Radiation Research Center, Hsinchu 30076 Taiwan, Republic of China
| | - Guangcun Shan
- School of Instrument Science and Optoelectronics Engineering & Institute of Precision Mechanics and Quantum Sensing, Beihang University, Beijing 100083, People's Republic of China.,Institute of Experimental Physics, Saarland University, 66123 Saarbrücken, Germany
| | - Svilen Bobev
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware 19716, United States
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13
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Guo Z, Hao X, Dong J, Li H, Gong Y, Yang D, Liao J, Chu S, Li Y, Li X, Chen D. Prediction of topological nontrivial semimetals and pressure-induced Lifshitz transition in 1T'-MoS 2 layered bulk polytypes. NANOSCALE 2020; 12:22710-22717. [PMID: 33169783 DOI: 10.1039/d0nr05208f] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Recently, bulk MoS2 crystals stacked by 1T'-MoS2 monolayers have been synthesized successfully, but little is known about their stacking sequences and topological properties. Based on first-principles calculations and symmetry-based indicator theory, we discovered that three predicted bulk structures of MoS2 (named 2M-, 1T'- and β-MoS2) stacked by 1T' monolayers are topological insulators and nodal line semimetals with and without spin-orbit coupling. Their stacking stability, electronic structure and the topology origin were systematically investigated. Further research proves that in the absence of SOC the open- and closed-type nodal lines can coexist in the momentum space of 2M-MoS2, which also possesses drumhead-like surface state. Moreover, we predicted a pressure-induced Lifshitz transition at about 1.3 GPa in 2M-MoS2. Our findings greatly enrich the topological phases of MoS2 and probably bring MoS2 to the rapidly growing family of layered topological semimetals.
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Affiliation(s)
- Zhiying Guo
- Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
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14
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Bhardwaj V, Bhattacharya A, Varga LK, Ganguli AK, Chatterjee R. Thickness-dependent magneto-transport properties of topologically nontrivial DyPdBi thin films. NANOTECHNOLOGY 2020; 31:384001. [PMID: 32503013 DOI: 10.1088/1361-6528/ab99f3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
DyPdBi (DPB) is a topological semimetal which belongs to the rare-earth-based half-Heusler alloy family. In this work, we studied the thickness-dependent structural and magneto-transport properties of DPB thin films (20 to 60 nm) grown using pulsed laser deposition. The DPB thin films show (110) oriented growth on MgO(100) single crystal substrates. Longitudinal resistance data indicate metallic surface states dominated carrier transport and the suppression of semiconducting bulk state carriers for films ≤40 nm. We observe the weak antilocalization (WAL) effect and Shubnikov-de Hass (SdH) oscillations in the magneto-transport data. The presence of a single coherent transport channel (α∼ -0.50) is observed in the Hikami-Larkin-Nagaoka (HLN) fitting of WAL data. The power law temperature dependence of phase coherence length (LØ ) ∼ T-0.50 indicates the observation of the 2D WAL effect and the presence of topological nontrivial surface states for films ≤40 nm. The 60 nm sample shows semiconducting resistivity behavior at higher temperature (>180 K) and HLN fitting results (α∼ -0.72, LØ ∼ T-0.68 ) indicate the presence of partial decoupled top and bottom surface states. The Berry phase ∼π is extracted for thin films ≤40 nm, which further demonstrates the presence of Dirac fermions and nontrivial surface states. Band structure parameters are extracted by fitting SdH data to the standard Lifshitz-Kosevich formula. The sheet carrier concentration and cyclotron effective mass of carriers decrease with increasing thickness (20 nm to 60 nm) from ∼1.35 × 1012 cm-2 to 0.68 × 1012 cm-2 and from ∼0.26 me to 0.12 me, respectively. Our observations suggest that samples with a thickness ≤40 nm have transport properties dominated by surface states and samples with a thickness ≥60 nm have contributions from both bulk and surface states.
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Affiliation(s)
- Vishal Bhardwaj
- Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India
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15
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Lu X, Liu H. The topological properties of D +p-wave superconductors in the mixed Rashba/Dresselhaus systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:455601. [PMID: 32717734 DOI: 10.1088/1361-648x/aba980] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2020] [Accepted: 07/27/2020] [Indexed: 02/28/2024]
Abstract
We investigate the effect of mixing Rashba/Dresselhaus spin-orbit couplings (SOCs) on the topological properties of D + p-wave superconductors. It is known that the nodal D + p-wave Rashba superconductors become gapful under a Zeeman magnetic field. We extend this gap-generation mechanism to mixed Rashba/Dresselhaus systems and find that the induced energy gaps are strongly modified by the Dresselhaus component in the second quadrant of the Brillion zone (BZ). We further calculate the Chern number numerically and obtain the topological phase diagram. It is shown that the Dresselhaus SOCs have a negative effect on the topological properties; the topological nontrivial region withC= -4 in the phase diagram shrinks as the amplitude of the Dresselhaus component increases. In the Dresselhaus-dominated regime, the contributions of gapped nodes from different quadrants of the BZ cancel each other, resulting in zero Chern number in most of the phase diagram. The numerical results are well explained by an approximate analytical formula for Chern number.
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Affiliation(s)
- Xiancong Lu
- Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China
| | - Hongxu Liu
- Department of Physics, Xiamen University, Xiamen 361005, People's Republic of China
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16
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Sahni B, Kangsabanik J, Alam A. Reliable Prediction of New Quantum Materials for Topological and Renewable-Energy Applications: A High-Throughput Screening. J Phys Chem Lett 2020; 11:6364-6372. [PMID: 32702983 DOI: 10.1021/acs.jpclett.0c01271] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Half-Heusler (HH) alloys provide a general platform for searching candidate materials for various energy applications. Here, we present a high-throughput first-principles calculation of a set of 960 eight valence-electron HH alloys to search potential candidates for thermoelectric (TE), solar harvesting (SH), topological insulator (TI), and transparent conductor (TC) applications. The initial screening parameters (such as stability, bandgap (Eg), band-inversion strength) followed by application specific descriptors are used to predict promising compounds. 121 out of 960 compounds were found to be dynamically and chemically stable. Of them, 31 compounds (with Eg < 1.5 eV) were studied for TE application, 30 (with 1 < Eg < 1.8 eV) for SH application, 21 for TI application, and 29 (with Eg > 2 eV) for TC applications. Some of the compounds show reasonably high thermoelectric figure of merit (ZT ∼ 1.6) and solar efficiency (SLME) > 20%, comparable to existing state-of-the-art materials. Surface band structure and topological Z2 index reconfirms the robustness of topological behavior. We strongly believe that our calculations should leverage useful insights to experimentalists.
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Affiliation(s)
- Bhawna Sahni
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
| | - Jiban Kangsabanik
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
| | - Aftab Alam
- Department of Physics, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
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17
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Observation of Dirac state in half-Heusler material YPtBi. Sci Rep 2020; 10:12343. [PMID: 32704042 PMCID: PMC7378050 DOI: 10.1038/s41598-020-69284-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 07/09/2020] [Indexed: 12/01/2022] Open
Abstract
The prediction of non-trivial topological electronic states in half-Heusler compounds makes these materials good candidates for discovering new physics and devices as half-Heusler phases harbour a variety of electronic ground states, including superconductivity, antiferromagnetism, and heavy-fermion behaviour. Here, we report a systematic studies of electronic properties of a superconducting half-Heusler compound YPtBi, in its normal state, investigated using angle-resolved photoemission spectroscopy. Our data reveal the presence of a Dirac state at the \documentclass[12pt]{minimal}
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\begin{document}$$\Gamma$$\end{document}Γ point of the Brillouin zone at 500 meV below the Fermi level. We observe the presence of multiple Fermi surface pockets, including two concentric hexagonal and six half-oval shaped pockets at the \documentclass[12pt]{minimal}
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\begin{document}$$\Gamma$$\end{document}Γ and K points of the Brillouin zone, respectively. Furthermore, our measurements show Rashba-split bands and multiple surface states crossing the Fermi level, this is also supported by the first-principles calculations. Our findings of a Dirac state in YPtBi contribute to the establishing of half-Heusler compounds as a potential platform for novel topological phases.
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18
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Mikaeilzadeh L, Tavana A, Khoeini F. Electronic structure of the PrNiBi half-Heusler system based on the σGGA + U method. Sci Rep 2019; 9:20075. [PMID: 31882907 PMCID: PMC6934805 DOI: 10.1038/s41598-019-56537-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 12/12/2019] [Indexed: 12/05/2022] Open
Abstract
In this works, we study the electronic structure and magnetic properties of the Pr-Ni-Bi half-Heusler systems based on density functional theory. We use the σ GGA + U scheme to consider the effects of on-site electron-electron interactions. Results show that in contrast to the rough estimation of the total magnetic moment of the unit cell, based on the Slater-Pauling behavior in the half-Heusler systems, this system has an antiferromagnetic ground state because of the localized Pr-f electrons. By increasing the magnitude of the effective U parameter, band-inversion occurs in the band structure of this system, which shows the possibility of topological state occurrence.
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Affiliation(s)
- L Mikaeilzadeh
- Department of Physics, University of Zanjan, Zanjan, 45195-313, Iran
| | - A Tavana
- AMDM Lab., Department of Physics, University of Mohaghegh Ardabili, Ardabil, 179, Iran
| | - F Khoeini
- Department of Physics, University of Zanjan, Zanjan, 45195-313, Iran.
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19
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Ni D, Guo S, Powderly KM, Zhong R, Cava RJ. A high-pressure phase with a non-centrosymmetric crystal structure in the PbSe–PbBr2 system. J SOLID STATE CHEM 2019. [DOI: 10.1016/j.jssc.2019.120982] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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20
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Souza JC, Jesus CBR, Lesseux GG, Rosa PFS, Urbano RR, Pagliuso PG. Crystalline electric field study in a putative topologically trivial rare-earth doped YPdBi compound. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:465701. [PMID: 31323656 DOI: 10.1088/1361-648x/ab33e9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Topological states of matter have attracted a lot of attention recently due to their intriguing physical properties and potential applications. In particular, the family of half-Heusler compounds [Formula: see text] (R = rare earth, M = Pt, Pd or Au, and T = Bi, Sb, Pb or Sn) has been predicted to display tunable topological properties via their cubic unit cell volume and/or the charges of the M and T atoms. In this work, we report electron spin resonance (ESR), along with complementary macroscopic experiments, in the putative topologically trivial rare-earth doped (Gd, Nd and Er) YPdBi. From magnetic susceptibility data analysis constrained by ESR results, we were able to extract the fourth (A 4) and sixth (A 6) order crystal field parameters (CFP) for YPdBi and compared them with those already reported to YPtBi, which is known as a topologically non-trivial compound. We observed that the sign of the CFP changes systematically from YPdBi to YPtBi, possibly due to the inversion of the valence and conduction bands at the Fermi level. The enhanced spin-orbit coupling in YPtBi, when compared to YPdBi, induces the band inversion that drives the system to a non-trivial topological state. This band inversion likely has an effect on the effective charges surrounding the magnetic dopants that are probed by the CFP.
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Affiliation(s)
- J C Souza
- Instituto de Física 'Gleb Wataghin', UNICAMP, Campinas-SP, 13083-859, Brazil
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21
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Zhu YL, Hu J, Womack FN, Graf D, Wang Y, Adams PW, Mao ZQ. Emergence of intrinsic superconductivity below 1.178 K in the topologically non-trivial semimetal state of CaSn 3. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:245703. [PMID: 30861508 DOI: 10.1088/1361-648x/ab0f0d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Topological materials which are also superconducting are of great current interest, since they may exhibit a non-trivial topologically-mediated superconducting phase. Although there have been many reports of pressure-tuned or chemical-doping-induced superconductivity in a variety of topological materials, there have been few examples of intrinsic, ambient pressure superconductivity in a topological system having a stoichiometric composition. Here, we report that the pure intermetallic CaSn3 not only exhibits topological fermion properties, but also has a superconducting phase at ~1.178 K under ambient pressure. The topological fermion properties, including the nearly zero quasi-particle mass and the non-trivial Berry phase accumulated in cyclotron motions, were revealed from the de Haas-van Alphen (dHvA) quantum oscillation studies of this material. Although CaSn3 was previously reported to be superconducting with T c = 4.2 K, our studies show that the T c = 4.2 K superconductivity is extrinsic and caused by Sn on the degraded surface, whereas its intrinsic bulk superconducting transition occurs at 1.178 K. These findings make CaSn3 a promising candidate for exploring new exotic states arising from the interplay between non-trivial band topology and superconductivity, e.g. topological superconductivity (TSC).
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Affiliation(s)
- Y L Zhu
- Physics and Engineering Physics department, Tulane University, New Orleans, LA 70118, United States of America
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22
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Hütt F, Yaresko A, Schilling MB, Shekhar C, Felser C, Dressel M, Pronin AV. Linear-in-Frequency Optical Conductivity in GdPtBi due to Transitions near the Triple Points. PHYSICAL REVIEW LETTERS 2018; 121:176601. [PMID: 30411916 DOI: 10.1103/physrevlett.121.176601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 08/29/2018] [Indexed: 06/08/2023]
Abstract
The complex optical conductivity of the half-Heusler compound GdPtBi is measured in a frequency range from 20 to 22 000 cm^{-1} (2.5 meV-2.73 eV) at temperatures down to 10 K in zero magnetic field. We find the real part of the conductivity, σ_{1}(ω), to be almost perfectly linear in frequency over a broad range from 50 to 800 cm^{-1} (∼6-100 meV) for T≤50 K. This linearity strongly suggests the presence of three-dimensional linear electronic bands with band crossings (nodes) near the chemical potential. Band-structure calculations show the presence of triple points, where one doubly degenerate and one nondegenerate band cross each other in close vicinity of the chemical potential. From a comparison of our data with the optical conductivity computed from the band structure, we conclude that the observed nearly linear σ_{1}(ω) originates as a cumulative effect from all the transitions near the triple points.
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Affiliation(s)
- F Hütt
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - A Yaresko
- Max-Planck-Institut für Festkörperforschung, 70569 Stuttgart, Germany
| | - M B Schilling
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - C Shekhar
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - C Felser
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - M Dressel
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
| | - A V Pronin
- 1. Physikalisches Institut, Universität Stuttgart, 70569 Stuttgart, Germany
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23
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Shekhar C, Kumar N, Grinenko V, Singh S, Sarkar R, Luetkens H, Wu SC, Zhang Y, Komarek AC, Kampert E, Skourski Y, Wosnitza J, Schnelle W, McCollam A, Zeitler U, Kübler J, Yan B, Klauss HH, Parkin SSP, Felser C. Anomalous Hall effect in Weyl semimetal half-Heusler compounds RPtBi (R = Gd and Nd). Proc Natl Acad Sci U S A 2018; 115:9140-9144. [PMID: 30154165 PMCID: PMC6140499 DOI: 10.1073/pnas.1810842115] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω-1⋅cm-1 and an anomalous Hall angle as large as 23%. Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition (TN) at 9 K without any noticeable magnetic correlations above TN Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE.
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Affiliation(s)
- Chandra Shekhar
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany;
| | - Nitesh Kumar
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - V Grinenko
- Institute for Solid State and Materials Physics, Faculty of Physics, Technische Universität Dresden, 01069 Dresden, Germany
- Leibniz Institute for Solid State and Materials Research Dresden, 01069 Dresden, Germany
| | - Sanjay Singh
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - R Sarkar
- Institute for Solid State and Materials Physics, Faculty of Physics, Technische Universität Dresden, 01069 Dresden, Germany
| | - H Luetkens
- Laboratory for Muon Spin Spectroscopy, Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland
| | - Shu-Chun Wu
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Yang Zhang
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | | | - Erik Kampert
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Yurii Skourski
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Jochen Wosnitza
- Institute for Solid State and Materials Physics, Faculty of Physics, Technische Universität Dresden, 01069 Dresden, Germany
- Dresden High Magnetic Field Laboratory (HLD-EMFL), Helmholtz-Zentrum Dresden-Rossendorf, 01328 Dresden, Germany
| | - Walter Schnelle
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Alix McCollam
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands
| | - Uli Zeitler
- High Field Magnet Laboratory (HFML-EMFL), Radboud University, 6525 ED Nijmegen, The Netherlands
| | - Jürgen Kübler
- Institute for Solid State Physics, Technische Universität Darmstadt, 64289 Darmstadt, Germany
| | - Binghai Yan
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - H-H Klauss
- Institute for Solid State and Materials Physics, Faculty of Physics, Technische Universität Dresden, 01069 Dresden, Germany
| | - S S P Parkin
- Max Planck Institute of Microstructure Physics, 06120 Halle, Germany
| | - C Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
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24
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Kim H, Wang K, Nakajima Y, Hu R, Ziemak S, Syers P, Wang L, Hodovanets H, Denlinger JD, Brydon PMR, Agterberg DF, Tanatar MA, Prozorov R, Paglione J. Beyond triplet: Unconventional superconductivity in a spin-3/2 topological semimetal. SCIENCE ADVANCES 2018; 4:eaao4513. [PMID: 29740606 PMCID: PMC5938259 DOI: 10.1126/sciadv.aao4513] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 02/15/2018] [Indexed: 05/05/2023]
Abstract
In all known fermionic superfluids, Cooper pairs are composed of spin-1/2 quasi-particles that pair to form either spin-singlet or spin-triplet bound states. The "spin" of a Bloch electron, however, is fixed by the symmetries of the crystal and the atomic orbitals from which it is derived and, in some cases, can behave as if it were a spin-3/2 particle. The superconducting state of such a system allows pairing beyond spin-triplet, with higher spin quasi-particles combining to form quintet or septet pairs. We report evidence of unconventional superconductivity emerging from a spin-3/2 quasi-particle electronic structure in the half-Heusler semimetal YPtBi, a low-carrier density noncentrosymmetric cubic material with a high symmetry that preserves the p-like j = 3/2 manifold in the Bi-based Γ8 band in the presence of strong spin-orbit coupling. With a striking linear temperature dependence of the London penetration depth, the existence of line nodes in the superconducting order parameter Δ is directly explained by a mixed-parity Cooper pairing model with high total angular momentum, consistent with a high-spin fermionic superfluid state. We propose a k ⋅ p model of the j = 3/2 fermions to explain how a dominant J = 3 septet pairing state is the simplest solution that naturally produces nodes in the mixed even-odd parity gap. Together with the underlying topologically nontrivial band structure, the unconventional pairing in this system represents a truly novel form of superfluidity that has strong potential for leading the development of a new series of topological superconductors.
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Affiliation(s)
- Hyunsoo Kim
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
- Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
- Corresponding author. (H.K.); (J.P.)
| | - Kefeng Wang
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Yasuyuki Nakajima
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Central Florida, Orlando, FL 32816, USA
| | - Rongwei Hu
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Steven Ziemak
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Paul Syers
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Limin Wang
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Halyna Hodovanets
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Jonathan D. Denlinger
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Philip M. R. Brydon
- Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand
| | | | - Makariy A. Tanatar
- Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
| | - Ruslan Prozorov
- Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
| | - Johnpierre Paglione
- Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA
- Department of Physics, University of Maryland, College Park, MD 20742, USA
- Corresponding author. (H.K.); (J.P.)
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25
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Cao G, Liu H, Chen XQ, Sun Y, Liang J, Yu R, Zhang Z. A simple and efficient criterion for ready screening of potential topological insulators. Sci Bull (Beijing) 2017; 62:1649-1653. [PMID: 36659384 DOI: 10.1016/j.scib.2017.11.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 11/15/2017] [Accepted: 11/16/2017] [Indexed: 01/21/2023]
Abstract
Topological materials are a new and rapidly expanding class of quantum matter. To date, identification of the topological nature of a given compound material demands specific determination of the appropriate topological invariant through detailed electronic structure calculations. Here we present an efficient criterion that allows ready screening of potential topological materials, using topological insulators as prototypical examples. The criterion is inherently tied to the band inversion induced by spin-orbit coupling, and is uniquely defined by a minimal number of two elemental physical properties of the constituent elements: the atomic number and Pauling electronegativity. The validity and predictive power of the criterion is demonstrated by rationalizing many known topological insulators and potential candidates in the tetradymite and half-Heusler families, and the underlying design principle is naturally also extendable to predictive discoveries of other classes of topological materials.
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Affiliation(s)
- Guohua Cao
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Huijun Liu
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China.
| | - Xing-Qiu Chen
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
| | - Yan Sun
- Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
| | - Jinghua Liang
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Rui Yu
- Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology, Wuhan University, Wuhan 430072, China
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China.
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26
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Wang Y, Fu L. Topological Phase Transitions in Multicomponent Superconductors. PHYSICAL REVIEW LETTERS 2017; 119:187003. [PMID: 29219538 DOI: 10.1103/physrevlett.119.187003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Indexed: 06/07/2023]
Abstract
We study the phase transition between a trivial and a time-reversal-invariant topological superconductor in a single-band system. By analyzing the interplay of symmetry, topology, and energetics, we show that for a generic normal state band structure, the phase transition occurs via extended intermediate phases in which even- and odd-parity pairing components coexist. For inversion-symmetric systems, the coexistence phase spontaneously breaks time-reversal symmetry. For noncentrosymmetric superconductors, the low-temperature intermediate phase is time-reversal breaking, while the high-temperature phase preserves time-reversal symmetry and has topologically protected line nodes. Furthermore, with approximate rotational invariance, the system has an emergent U(1)×U(1) symmetry, and novel topological defects, such as half vortex lines binding Majorana fermions, can exist. We analytically solve for the dispersion of the Majorana fermion and show that it exhibits small and large velocities at low and high energies. Relevance of our theory to superconducting pyrochlore oxide Cd_{2}Re_{2}O_{7} and half-Heusler materials is discussed.
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Affiliation(s)
- Yuxuan Wang
- Department of Physics and Institute for Condensed Matter Theory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801-3080, USA
| | - Liang Fu
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Yang H, Yu J, Parkin SSP, Felser C, Liu CX, Yan B. Prediction of Triple Point Fermions in Simple Half-Heusler Topological Insulators. PHYSICAL REVIEW LETTERS 2017; 119:136401. [PMID: 29341689 DOI: 10.1103/physrevlett.119.136401] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Indexed: 06/07/2023]
Abstract
We predict the existence of triple point fermions in the band structure of several half-Heusler topological insulators by ab initio calculations and the Kane model. We find that many half-Heusler compounds exhibit multiple triple points along four independent C_{3} axes, through which the doubly degenerate conduction bands and the nondegenerate valence band cross each other linearly nearby the Fermi energy. When projected from the bulk to the (111) surface, most of these triple points are located far away from the surface Γ[over ¯] point, as distinct from previously reported triple point fermion candidates. These isolated triple points give rise to Fermi arcs on the surface, that can be readily detected by photoemission spectroscopy or scanning tunneling spectroscopy.
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Affiliation(s)
- Hao Yang
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - Jiabin Yu
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Stuart S P Parkin
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany
| | - Claudia Felser
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Chao-Xing Liu
- Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Binghai Yan
- Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 7610001, Israel
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28
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Xu G, Hou Z, Wang Y, Zhang X, Zhang H, Liu E, Xi X, Xu F, Wu G, Zhang XX, Wang W. Angle-dependent magnetoresistance and quantum oscillations in high-mobility semimetal LuPtBi. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:195501. [PMID: 28290375 DOI: 10.1088/1361-648x/aa6695] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The recent discovery of ultrahigh mobility and large positive magnetoresistance in the topologically non-trivial half-Heusler semimetal LuPtBi provides a unique playground for studying exotic physics and significant perspective for device applications. As an fcc-structured electron-hole-compensated semimetal, LuPtBi theoretically exhibits six symmetrically arranged anisotropic electron Fermi pockets and two nearly-spherical hole pockets, offering the opportunity to explore the physics of Fermi surfaces with simple angle-related magnetotransport properties. In this work, through angle-dependent transverse magnetoresistance measurements, in combination with high-field SdH quantum oscillations, we aimed to map out a Fermi surface with six anisotropic pockets in the high-temperature and low-field regime, and furthermore, identify a possible magnetic field driven Fermi surface change at lower temperatures. Reasons account for the Fermi surface change in LuPtBi are discussed in terms of the field-induced electron evacuation due to Landau quantization.
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Affiliation(s)
- Guizhou Xu
- School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, People's Republic of China. State Key Laboratory for Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
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Affiliation(s)
- Weiwei Xie
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Lea Gustin
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Guang Bian
- Department of Physics & Astronomy, University of Missouri, Columbia, Missouri 65201, United States
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30
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Multiple Dirac cones at the surface of the topological metal LaBi. Nat Commun 2017; 8:13942. [PMID: 28067241 PMCID: PMC5227739 DOI: 10.1038/ncomms13942] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 11/15/2016] [Indexed: 11/17/2022] Open
Abstract
The rare-earth monopnictide LaBi exhibits exotic magneto-transport properties, including an extremely large and anisotropic magnetoresistance. Experimental evidence for topological surface states is still missing although band inversions have been postulated to induce a topological phase in LaBi. In this work, we have revealed the existence of surface states of LaBi through the observation of three Dirac cones: two coexist at the corners and one appears at the centre of the Brillouin zone, by employing angle-resolved photoemission spectroscopy in conjunction with ab initio calculations. The odd number of surface Dirac cones is a direct consequence of the odd number of band inversions in the bulk band structure, thereby proving that LaBi is a topological, compensated semimetal, which is equivalent to a time-reversal invariant topological insulator. Our findings provide insight into the topological surface states of LaBi's semi-metallicity and related magneto-transport properties. The magnetoresistance suggests an exotic topological phase in LaBi, but the evidence is still missing. Here, Nayak et al. report the existence of surface states of LaBi through the observation of three Dirac cones, confirming it a topological semimetal.
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