Disorder-induced orbital ordering in doped manganites

Kumar, Sanjeev; Kampf, Arno P.

doi:10.1103/physrevb.77.134442

Cited by 9 publications

(21 citation statements)

References 34 publications

(75 reference statements)

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“…Thus, variance induced disorder effects can be recognized by the sudden onset of structural reorientation producing large discontinuous changes in transition temperature and resistive behavior. Moreover, magnetic moments tend to strongly decrease with increased variance [40,41]. The disorder mechanism is thus ruled out for our results, since there is no evidence of sudden changes in crystal structure, transition temperature, resistivity, or low temperature moment as a function of the He implantation dose.…”

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confidence: 67%

“…However, the large changes in transition temperature observed in materials of high A-site variance in those systems are associated with an orthorhombic (O 00 ) to orthorhombic (O 0 ) structural phase change as discussed in Refs. [40,41]. An increased variance in the orbitally disordered O 00 phase leads to a slight decrease in transition temperature of ∼20°C.…”

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confidence: 99%

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Strain Doping: Reversible Single-Axis Control of a Complex Oxide Lattice via Helium Implantation

et al. 2015

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We report on the use of helium ion implantation to independently control the out-of-plane lattice constant in epitaxial La 0.7 Sr 0.3 MnO 3 thin films without changing the in-plane lattice constants. The process is reversible by a vacuum anneal. Resistance and magnetization measurements show that even a small increase in the out-of-plane lattice constant of less than 1% can shift the metal-insulator transition and Curie temperatures by more than 100°C. Unlike conventional epitaxy-based strain tuning methods which are constrained not only by the Poisson effect but by the limited set of available substrates, the present study shows that strain can be independently and continuously controlled along a single axis. This permits novel control over orbital populations through Jahn-Teller effects, as shown by Monte Carlo simulations on a double-exchange model. The ability to reversibly control a single lattice parameter substantially broadens the phase space for experimental exploration of predictive models and leads to new possibilities for control over materials' functional properties. The crystal lattice is one of the most accessible degrees of freedom in materials. In complex oxides, effective control over lattice parameters not only facilitates the understanding of multiple interactions in strongly correlated systems, but also creates new phases and emergent functionalities [1][2][3][4]. Lattice engineering has played an extremely important role in attempts to design strongly correlated systems and has led to many important discoveries [1,[5][6][7][8]. Control over lattice strain in films using different substrates [9] has revealed enhanced ferroelectricity [10] and superconductivity [11], as well as induced superconductivity in otherwise nonsuperconducting compounds [12]. However, the basic nature of the broken translational symmetry in the crystal lattice also entails a rigidity against arbitrary control [13]. There is so far no experimental technique that allows one to alter the lattice parameter solely along a single crystal axis, i.e., with an effective Poisson's ratio of zero. For strain engineering in systems with a nonzero Poisson ratio, the lattice constant, and hence the electronic structure, necessarily change in all three directions, clouding the cause-effect relations between single degrees of freedom and order parameters.We demonstrate an approach using helium implantation to effectively "strain dope" the lattice along a single axis of a La 0.7 Sr 0.3 MnO 3 (LSMO) film that is epitaxially latticelocked to a substrate. The out-of-plane (c-axis) lattice constant can be modified independently of the in-plane lattice constants. The c-axis strain can be continuously manipulated, and is thus not restricted by the limited collection of substrates that dictate conventional epitaxial strain engineering. The change in materials' properties, while reversible via a high temperature anneal, is persistent even well above room temperature. No continuous external actuation is required as with transient pressure-induc...

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Strain Doping: Reversible Single-Axis Control of a Complex Oxide Lattice via Helium Implantation

et al. 2015

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“…Based on the studies on the first slave-particle approach [45], it has been argued that slave-particle approaches are equivalent to a statisticallyconsistent Gutzwiller approximation [46][47][48]. Recently, a constraint-free, invertible canonical slave-spin transformation has been proposed for strongly correlated systems [49,50]. This slave-spin transformation is more effective than other slave-particle transformations as the basis states of the Hilbert spaces of a particle on a single site has one-to-one mapping.…”

Section: Slave-rotor Mean-field Theorymentioning

confidence: 99%

Theoretical phase diagram of unconventional alkali-doped fullerides

Silva

2019

Phys. Rev. B

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By constructing an effective model based on recently calculated ab initio bare interaction parameters, we study the phase diagram of alkali doped fullerides as a function of temperature and internal pressure. We use a slave-rotor mean-field approach at the weak and intermediate coupling limits and a variational mean-field approach at the strong coupling limit, and find a good agreement with experimental phase diagram. We explain the unified description of the phase diagram including the proximity of s-wave superconducting state and the Mott-insulating state, and the existence of Jahn-Teller distorted metallic state using orbital selective physics. We argue that the double electronic occupation of two degenerate orbitals triggers both s-wave superconductivity and Jahn-Teller distortion. While the orbital ordering of two electrons causes the distortion, the remaining single electron in the third orbital causes the metal-insulator transition.

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“…There are no systemic theory studies on an entire serie of Pt clusters with large sizes. [85,86] The theory study can offer insight into the mechanism of the catalytic reaction and molecular interaction, and thus is extremely important. We here first use PDECO to optimize the Pt clusters with the size from 3 to 130, and analyze their structure properties.…”

Section: Full Papermentioning

confidence: 99%

PDECO: Parallel differential evolution for clusters optimization

Chen

Jiang

et al. 2013

J Comput Chem

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The optimization of the atomic and molecular clusters with a large number of atoms is a very challenging topic. This article proposes a parallel differential evolution (DE) optimization scheme for large-scale clusters. It combines a modified DE algorithm with improved genetic operators and a parallel strategy with a migration operator to address the problems of numerous local optima and large computational demanding. Results of Lennard-Jones (LJ) clusters and Gupta-potential Co clusters show the performance of the algorithm surpasses those in previous researches in terms of successful rate, convergent speed, and global searching ability. The overall performance for large or challenging LJ clusters is enhanced significantly. The average number of local minimizations per hit of the global minima for Co clusters is only about 3-4% of that in previous methods. Some global optima for Co are also updated. We then apply the algorithm to optimize the Pt clusters with Gupta potential from the size 3 to 130 and analyze their electronic properties by density functional theory calculation. The clusters with 13, 38, 54, 75, 108, and 125 atoms are extremely stable and can be taken as the magic numbers for Pt systems. It is interesting that the more stable structures, especially magic-number ones, tend to have a larger energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital. It is also found that the clusters are gradually close to the metal bulk from the size N > 80 and Pt38 is expected to be more active than Pt75 in catalytic reaction.

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Disorder-induced orbital ordering in doped manganites

Cited by 9 publications

References 34 publications

Strain Doping: Reversible Single-Axis Control of a Complex Oxide Lattice via Helium Implantation

Strain Doping: Reversible Single-Axis Control of a Complex Oxide Lattice via Helium Implantation

Theoretical phase diagram of unconventional alkali-doped fullerides

PDECO: Parallel differential evolution for clusters optimization

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