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Singh K, Sihi A, Pandey SK, Mukherjee K. Evidence of charge susceptibility and multiple f- chybridization configurations with the La doping in CeGe: a DFT + DMFT study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2023; 35. [PMID: 37161911 DOI: 10.1088/1361-648x/acd09a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2023] [Accepted: 04/26/2023] [Indexed: 05/11/2023]
Abstract
Kondo coupling has been extensively investigated in several Ce-based systems. However, the search for materials showing the interplay between the Kondo effect, spin-orbit interaction, and crystal-field effect along with the presence of local charge susceptibility; remains a challenge for the condensed matter community. Actually, in Ce-based systems, the strong coupling of the conduction electrons to the local magnetic moments usually hides these properties. Here, we present a detailed investigation of Ce0.6La0.4Ge through a combined density functional theory and dynamic mean-field theory study. Our investigations give evidence of the significant charge susceptibility and the multiple differentf-chybridization configurations. The weakening of the magnetization owing to the dilution of the Ce-site is the main cause for the appearance of such properties, which is believed to occur due to the presence of the relevant local moment andf-chybridization over the competition with the on-site Coulomb interaction.
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Affiliation(s)
- Karan Singh
- School of Physical Sciences, Indian Institute of Technology Mandi, Mandi 175075, Himachal Pradesh, India
| | - Antik Sihi
- School of Physical Sciences, Indian Institute of Technology Mandi, Mandi 175075, Himachal Pradesh, India
| | - Sudhir K Pandey
- School of Mechanical and Materials Engineering, Indian Institute of Technology Mandi, Mandi 175075, Himachal Pradesh, India
| | - K Mukherjee
- School of Physical Sciences, Indian Institute of Technology Mandi, Mandi 175075, Himachal Pradesh, India
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Pi ST, Savrasov SY, Pickett WE. Pressure-tuned Frustration of Magnetic Coupling in Elemental Europium. PHYSICAL REVIEW LETTERS 2019; 122:057201. [PMID: 30822011 DOI: 10.1103/physrevlett.122.057201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Revised: 12/26/2018] [Indexed: 06/09/2023]
Abstract
Applying linear response and the magnetic force theorem in correlated density functional theory, the intersublattice exchange constants of antiferromagnetic Eu are calculated and found to vanish near the pressure of P_{c}=82 GPa, just where magnetic order is observed experimentally to be lost. The Eu 4f^{7} moment remains unchanged at high pressure, again in agreement with spectroscopic measurements, leaving the picture of perfect frustration of interatomic Ruderman-Kittel-Kasuya-Yoshida couplings in a broad metallic background, leaving a state of electrons strongly exchange coupled to arbitrarily oriented, possibly quasistatic local moments. This strongly frustrated state gives way to superconductivity at T_{c}=1.7 K, observed experimentally. These phenomena, and free energy considerations related to correlations, suggest an unusual phase of matter that is discussed within the scenarios of the Doniach Kondo lattice phase diagram, the metallic spin glass class, and itinerant spin liquid or spin gas systems.
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Affiliation(s)
- Shu-Ting Pi
- Department of Physics, University of California Davis, Davis, California 95616 USA
| | - Sergey Y Savrasov
- Department of Physics, University of California Davis, Davis, California 95616 USA
| | - Warren E Pickett
- Department of Physics, University of California Davis, Davis, California 95616 USA
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Lu H, Huang L. Electronic correlations in cerium's high-pressure phases. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:395601. [PMID: 30136653 DOI: 10.1088/1361-648x/aadc7c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Under high pressure, cerium exhibits three distinct phases, namely [Formula: see text], [Formula: see text], and ϵ-cerium. It is unclear whether the 4f electronic correlations will play a vital role in these phases or not. By utilizing the combination of traditional density functional theory and single-site dynamical mean-field theory, we tried to calculate the electronic structures of cerium's high-pressure phases. Their momentum-resolved spectral functions, total and 4f partial density of states, local self-energy functions, and 4f electronic configurations were exhaustively studied. The calculated results show that the correlated 4f bands strongly hybridize with the conducting spd bands around the Fermi level. The Matsubara self-energy functions exhibit Fermi-liquid like characteristic in the low-frequency regime. In addition, the fluctuations among the 4f atomic eigenstates are somewhat prominent (especially for the ϵ phase), which lead to slight modification of the 4f occupancy. It is suggested that the 4f electrons in these phases tend to be itinerant.
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Affiliation(s)
- Haiyan Lu
- Science and Technology on Surface Physics and Chemistry Laboratory, PO Box 9-35, Jiangyou 621908, People's Republic of China
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Song J, Fabbris G, Bi W, Haskel D, Schilling JS. Pressure-Induced Superconductivity in Elemental Ytterbium Metal. PHYSICAL REVIEW LETTERS 2018; 121:037004. [PMID: 30085803 DOI: 10.1103/physrevlett.121.037004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2018] [Revised: 03/30/2018] [Indexed: 06/08/2023]
Abstract
Ytterbium (Yb) metal is divalent and nonmagnetic (4f^{14} configuration). Under pressure its valence increases significantly leading to the expectation that magnetic instabilities and other highly correlated electron effects may appear before a stable trivalent state is reached (4f^{13} configuration). We carried out electrical resistivity and ac magnetic susceptibility measurements to 179 GPa over the temperature range 1.4-295 K. No evidence for magnetic order is observed. However, Yb becomes a superconductor at 86 GPa with T_{c}≃1.4 K, increasing to 4.6 K at 179 GPa. X-ray absorption spectroscopy shows that Yb remains mixed valent to at least 125 GPa, pointing to an active role of f electrons in the emergence of superconductivity in this simple, elemental solid.
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Affiliation(s)
- J Song
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - G Fabbris
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - W Bi
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
- Department of Geology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | - D Haskel
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - J S Schilling
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
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Mazet T, Malterre D, François M, Dallera C, Grioni M, Monaco G. Nonpareil Yb behavior in YbMn6Ge(6-x)Sn(x). PHYSICAL REVIEW LETTERS 2013; 111:096402. [PMID: 24033054 DOI: 10.1103/physrevlett.111.096402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Indexed: 06/02/2023]
Abstract
We investigate the temperature dependence of the Yb valence in YbMn6Ge1.8Sn4.2 and YbMn6Ge1.6Sn4.4 using resonant inelastic x-ray scattering experiments. Yb is found to be in an intermediate valent state in the whole investigated temperature range (10-450 K). We thus prove that the unusually high magnetic ordering temperature of Yb (∼60 and 90 K for x=4.2 and 4.4, respectively) involves an intermediate valent Yb, an unprecedentedly observed phenomenon. Further, an anomalous increase in the Yb valence is observed upon cooling. A scenario is proposed to explain this unusual behavior. It is based on the presence of magnetically ordered Mn moments and on an Anderson Hamiltonian with a Zeeman term modeling the magnetic interactions.
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Affiliation(s)
- T Mazet
- Institut Jean Lamour, UMR 7198, Université de Lorraine-Boîte Postale 70239, 54506 Vandœuvre-lès-Nancy, France
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Lu F, Zhao J, Weng H, Fang Z, Dai X. Correlated topological insulators with mixed valence. PHYSICAL REVIEW LETTERS 2013; 110:096401. [PMID: 23496729 DOI: 10.1103/physrevlett.110.096401] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Indexed: 06/01/2023]
Abstract
We propose the local density approximation+Gutzwiller method incorporating a Green's function scheme to study the topological physics of correlated materials from the first principles. Applying this method to typical mixed valence materials SmB(6), we find its nontrivial Z(2) topology, indicating that SmB(6) is a strongly correlated topological insulator. The unique feature of this compound is that its surface states contain three Dirac cones in contrast to most known topological insulators.
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Affiliation(s)
- Feng Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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Kuneš J, Křápek V, Parragh N, Sangiovanni G, Toschi A, Kozhevnikov AV. Spin state of negative charge-transfer material SrCoO(3). PHYSICAL REVIEW LETTERS 2012; 109:117206. [PMID: 23005672 DOI: 10.1103/physrevlett.109.117206] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Indexed: 06/01/2023]
Abstract
We employ the combination of the density functional theory and the dynamical mean-field theory to investigate the electronic structure and magnetic properties of SrCoO(3), monocrystals of which were prepared recently. Our calculations lead to a ferromagnetic metal in agreement with experiment. We find that, contrary to some suggestions, the local moment in SrCoO(3) does not arise from intermediate spin state, but is a result of coherent superposition of many different atomic states. We discuss how the attribution of magnetic response to different atomic states in solids with local moments can be quantified.
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Affiliation(s)
- J Kuneš
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, Praha 6, 162 53, Czech Republic
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Kumar P, Vidhyadhiraja NS. From mixed valence to the Kondo lattice regime. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:485601. [PMID: 22080675 DOI: 10.1088/0953-8984/23/48/485601] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Many heavy fermion materials are known to cross over from the Kondo lattice regime to the mixed valence regime or vice versa as a function of pressure or doping. We study this crossover theoretically by employing the periodic Anderson model within the framework of the dynamical mean field theory. Changes occurring in the dynamics and transport across this crossover are highlighted. As the valence is decreased (increased) relative to the Kondo lattice regime, the Kondo resonance broadens significantly, while the lower (upper) Hubbard band moves closer to the Fermi level. The resistivity develops a two peak structure in the mixed valence regime: a low temperature coherence peak and a high temperature 'Hubbard band' peak. These two peaks merge, yielding a broad shallow maximum upon decreasing the valence further. The optical conductivity likewise exhibits an unusual absorption feature (shoulder) in the deep mid-infrared region, which grows in intensity with decreasing valence. The involvement of the Hubbard bands in dc transport and of the effective f-level in the optical conductivity are shown to be responsible for the anomalous transport properties. A two-band hybridization-gap model, which neglects incoherent effects due to many-body scattering, commonly employed to understand the optical response in these materials is shown to be inadequate, especially in the mixed valence regime. Comparison of theory with experiment carried out for (a) dc resistivities of CeRhIn(5), Ce(2)Ni(3)Si(5), CeFeGe(3) and YbIr(2)Si(2), (b) pressure dependent resistivity of YbInAu(2) and CeCu(6), and (c) optical conductivity measurements in YbIr(2)Si(2) yields excellent agreement.
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Affiliation(s)
- Pramod Kumar
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bengaluru, India
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