scholarly journals Emergent helical texture of electric dipoles

Science ◽  
2020 ◽  
Vol 369 (6504) ◽  
pp. 680-684 ◽  
Author(s):  
Dmitry D. Khalyavin ◽  
Roger D. Johnson ◽  
Fabio Orlandi ◽  
Paolo G. Radaelli ◽  
Pascal Manuel ◽  
...  
Keyword(s):  
Electric Dipole ◽  
Density Wave ◽  
Exchange Interactions ◽  
Hole Doping ◽  
Orbital Ordering ◽  
Magnetic Dipoles ◽  
Magnetic Structures ◽  
Dipolar Order ◽  
Electric Dipoles ◽  
Long Range Ordering

Long-range ordering of magnetic dipoles in bulk materials gives rise to a broad range of magnetic structures, from simple collinear ferromagnets and antiferromagnets, to complex magnetic helicoidal textures stabilized by competing exchange interactions. In contrast, dipolar order in dielectric crystals is typically limited to parallel (ferroelectric) and antiparallel (antiferroelectric) collinear alignments of electric dipoles. Here, we report an observation of incommensurate helical ordering of electric dipoles by light hole doping of the quadruple perovskite BiMn7O12. In analogy with magnetism, the electric dipole helicoidal texture is stabilized by competing instabilities. Specifically, orbital ordering and lone electron pair stereochemical activity compete, giving rise to phase transitions from a nonchiral cubic structure to an incommensurate electric dipole and orbital helix via an intermediate density wave.

Phase Diagram and Anisotropic Transport Properties of Nd1-xSrxMnO3 Crystals

1997 ◽  
Vol 494 ◽  
Author(s):  
H. Kuwahara ◽  
T. Okuda ◽  
Y. Tomioka ◽  
T. Kimura ◽  
A. Asamitsu ◽  
...  
Keyword(s):  
Phase Diagram ◽  
Transport Properties ◽  
Lattice Parameter ◽  
Hole Doping ◽  
Orbital Ordering ◽  
Metallic Behavior ◽  
Magnetic Structures ◽  
Electronic Phase ◽  
Spin Polarized ◽  
Perovskite Type

ABSTRACTWe have investigated electronic transport and magnetic properties of perovskite-type Nd1-xSrxMnO3 crystals with change of controlled hole-doping level (0.30≤x≤0.80). The electronic phase diagram of Nd1-xSrxMnO3 was obtained by systematic measurements of magnetization (magnetic structure), resistivity, and lattice parameter. We have also studied the anisotropie transport properties of x=0.50 and 0.55 crystals with different magnetic structures: CE-type antiferromagnetic (AF) structure for x=0.50 and A-type layered AF one for x=0.55. In the case of the x=0.55 crystal, the metallic behavior was observed within the ferromagnetic (F) layers, while along the AF-coupling direction the crystal remains insulating over the whole temperature region. The observed large anisotropy is due to the magnetic as well as orbital-ordering induced confinement of the spin-polarized carriers within the F sheets. The nearly isotropie transport behavior has been confirmed for the CE-type AF charge-ordered state in the x=0.50 crystal.

Size-dependent emission of a dipole coupled to a metal nanoparticle

MRS Advances ◽  
2020 ◽  
Vol 5 (62) ◽  
pp. 3315-3325
Author(s):  
Viktoriia Savchuk ◽  
Arthur R. Knize ◽  
Pavlo Pinchuk ◽  
Anatoliy O. Pinchuk
Keyword(s):  
Numerical Analysis ◽  
Quantum Yield ◽  
Electric Dipole ◽  
Incident Radiation ◽  
Metal Nanoparticle ◽  
Plasmonic Nanoparticle ◽  
Size Dependent ◽  
Emission Enhancement ◽  
Electric Dipoles

AbstractWe present a systematic numerical analysis of the quantum yield of an electric dipole coupled to a plasmonic nanoparticle. We observe that the yield is highly dependent on the distance between the electric dipole and the nanoparticle, the size and permittivity of the nanoparticle, and the wavelength of the incident radiation. Our results indicate that enhancement of the quantum yield is only possible for electric dipoles coupled to a nanoparticle with a radius of 20 nm or larger. As the size of the nanoparticle is increased, emission enhancement occurs at wavelengths dependent on the coupling distance.

scholarly journals Nanostructured and Modulated Low-Dimensional Systems

2013 ◽  
Vol 203-204 ◽  
pp. 42-47
Author(s):  
Albert Prodan ◽  
Herman J.P. van Midden ◽  
Erik Zupanič ◽  
Rok Žitko
Keyword(s):  
Charge Density ◽  
Structural Information ◽  
Density Wave ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Additional Information ◽  
Related Pair ◽  
Good Accord ◽  
Long Range Ordering ◽  
Low Dimensional

Charge density wave (CDW) ordering in NbSe3 and the structurally related quasi one-dimensional compounds is reconsidered. Since the modulated ground state is characterized by unstable nano-domains, the structural information obtained from diffraction experiments is to be supplemented by some additional information from a method, able to reveal details on a unit cell level. Low-temperature (LT) scanning tunneling microscopy (STM) can resolve both, the local atomic structure and the superimposed charge density modulation. It is shown that the established model for NbSe3 with two incommensurate (IC) modes, q1 = (0,0.241,0) and q2 = (0.5,0.260,0.5), locked in at T1=144K and T2=59K and separately confined to two of the three available types of bi-capped trigonal prismatic (BCTP) columns, must be modified. The alternative explanation is based on the existence of modulated layered nano-domains and is in good accord with the available LT STM results. These confirm i.a. the presence of both IC modes above the lower CDW transition temperature. Two BCTP columns, belonging to a symmetry-related pair, are as a rule alternatively modulated by the two modes. Such pairs of columns are ordered into unstable layered nano-domains, whose q1 and q2 sub-layers are easily interchanged. The mutually interchangeable sections of the two unstable IC modes keep a temperature dependent long-range ordering. Both modes can formally be replaced by a single highly inharmonic long-period commensurate CDW.

scholarly journals Влияние орбитального упорядочения на спектры магнитного резонанса в зарядово-упорядоченных и фрустрированных манганитах

2019 ◽  
Vol 61 (5) ◽  
pp. 841
Author(s):  
Л.Э. Гончарь
Keyword(s):  
Metal Ion ◽  
Alkaline Earth ◽  
Theoretical Study ◽  
Earth Metal ◽  
Exchange Interactions ◽  
Alkaline Earth Metal ◽  
Antiferromagnetic Resonance ◽  
Rare Earth Ion ◽  
Magnetic Structures ◽  
Low Dimensional

A theoretical study of the interrelation of the crystal structure, charge, orbital, and magnetic subsystems in R1–xAxMnO3 charge-ordered manganites has been carried out (where R3+ is the rare earth ion, A2+ is the alkaline earth metal ion, x = 0.5, 2/3). The model of orbital-dependent exchange interactions and single-ion anisotropy is used. The presence of quasi-low-dimensional magnetic structures is exhibited. The spin waves spectra and antiferromagnetic resonance spectra are calculated.

Long-range exchange interactions in epitaxial layered magnetic structures

1996 ◽  
Vol 221 (1-4) ◽  
pp. 357-365 ◽  
Author(s):  
P. Grünberg ◽  
J.A. Wolf ◽  
R. Schäfer
Keyword(s):  
Long Range ◽  
Exchange Interactions ◽  
Magnetic Structures

Phase Transitions in Hoalga

1983 ◽  
Vol 21 ◽  
Author(s):  
M. Doukoure ◽  
D. Gignoux ◽  
F. Sayetat
Keyword(s):  
Thermal Expansion ◽  
Room Temperature ◽  
Magnetic Order ◽  
Magnetocrystalline Anisotropy ◽  
Exchange Interactions ◽  
Thermal Anomaly ◽  
Antiferromagnetic State ◽  
Hexagonal Symmetry ◽  
X Ray ◽  
Magnetic Structures

ABSTRACTHoAlGa is hexagonal at room temperature. It undergoes two magnetic transitions succesively at TN = 32 K from a paramagnetic to a triangular antiferromagnetic state where the Ho moments lie in the basal plane and at Tt = 18 K in the course of which the moments rotate toward c giving rise to a colinear antiferromagnetic arrangement. X-ray experiments performed between 5 and 300 K allow to determine the crystal evolution through the two transitions. The hexagonal symmetry is not lowered through the transitions; this result is compatible with the observed magnetic groups. The thermal expansion curves show a very anisotropic behaviour of the lattice parameters. The “c” parameter shrinks below TN and this anomaly is to be related to the magnetic order. Along a, a positive thermal anomaly appears below 70 K and this can be interpreted by crystal field effects. Stability of magnetic structures is discussed with regard to exchange interactions and magnetocrystalline anisotropy.

scholarly journals The “Loopole” Antenna: A Hybrid Coil Combining Loop and Electric Dipole Properties for Ultra-High-Field MRI

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Karthik Lakshmanan ◽  
Martijn Cloos ◽  
Ryan Brown ◽  
Riccardo Lattanzi ◽  
Daniel K. Sodickson ◽  
...  
Keyword(s):  
Current Distribution ◽  
Electric Dipole ◽  
High Field ◽  
High Performance ◽  
Signal To Noise Ratio ◽  
Ultra High Field ◽  
High Field Mri ◽  
Electric Dipoles ◽  
Ultra High Field Mri ◽  
Free Current

Purpose. To revisit the “loopole,” an unusual coil topology whose unbalanced current distribution captures both loop and electric dipole properties, which can be advantageous in ultra-high-field MRI. Methods. Loopole coils were built by deliberately breaking the capacitor symmetry of traditional loop coils. The corresponding current distribution, transmit efficiency, and signal-to-noise ratio (SNR) were evaluated in simulation and experiments in comparison to those of loops and electric dipoles at 7 T (297 MHz). Results. The loopole coil exhibited a hybrid current pattern, comprising features of both loops and electric dipole current patterns. Depending on the orientation relative to B0, the loopole demonstrated significant performance boost in either the transmit efficiency or SNR at the center of a dielectric sample when compared to a traditional loop. Modest improvements were observed when compared to an electric dipole. Conclusion. The loopole can achieve high performance by supporting both divergence-free and curl-free current patterns, which are both significant contributors to the ultimate intrinsic performance at ultra-high field. While electric dipoles exhibit similar hybrid properties, loopoles maintain the engineering advantages of loops, such as geometric decoupling and reduced resonance frequency dependence on sample loading.

scholarly journals Evidence for a vestigial nematic state in the cuprate pseudogap phase

2019 ◽  
Vol 116 (27) ◽  
pp. 13249-13254 ◽  
Author(s):  
Sourin Mukhopadhyay ◽  
Rahul Sharma ◽  
Chung Koo Kim ◽  
Stephen D. Edkins ◽  
Mohammad H. Hamidian ◽  
...  
Keyword(s):  
Fermi Surface ◽  
Energy Gap ◽  
Density Wave ◽  
Broken Symmetry ◽  
Hole Doping ◽  
Thermal Transitions ◽  
Electronic Density ◽  
Pseudogap Phase ◽  
Nematic State ◽  
Gap Opening

The CuO2 antiferromagnetic insulator is transformed by hole-doping into an exotic quantum fluid usually referred to as the pseudogap (PG) phase. Its defining characteristic is a strong suppression of the electronic density-of-states D(E) for energies |E| < Δ*, where Δ* is the PG energy. Unanticipated broken-symmetry phases have been detected by a wide variety of techniques in the PG regime, most significantly a finite-Q density-wave (DW) state and a Q = 0 nematic (NE) state. Sublattice-phase-resolved imaging of electronic structure allows the doping and energy dependence of these distinct broken-symmetry states to be visualized simultaneously. Using this approach, we show that even though their reported ordering temperatures TDW and TNE are unrelated to each other, both the DW and NE states always exhibit their maximum spectral intensity at the same energy, and using independent measurements that this is the PG energy Δ*. Moreover, no new energy-gap opening coincides with the appearance of the DW state (which should theoretically open an energy gap on the Fermi surface), while the observed PG opening coincides with the appearance of the NE state (which should theoretically be incapable of opening a Fermi-surface gap). We demonstrate how this perplexing phenomenology of thermal transitions and energy-gap opening at the breaking of two highly distinct symmetries may be understood as the natural consequence of a vestigial nematic state within the pseudogap phase of Bi2Sr2CaCu2O8.

scholarly journals Superconductivity in the doped Hubbard model and its interplay with next-nearest hopping t′

Science ◽  
2019 ◽  
Vol 365 (6460) ◽  
pp. 1424-1428 ◽  
Author(s):  
Hong-Chen Jiang ◽  
Thomas P. Devereaux
Keyword(s):  
Hubbard Model ◽  
Charge Density ◽  
Spin Density ◽  
Charge Density Wave ◽  
Large Scale ◽  
Nearest Neighbor ◽  
High Temperature Superconductivity ◽  
Density Wave ◽  
Spin Density Wave ◽  
Hole Doping

The Hubbard model is widely believed to contain the essential ingredients of high-temperature superconductivity. However, proving definitively that the model supports superconductivity is challenging. Here, we report a large-scale density matrix renormalization group study of the lightly doped Hubbard model on four-leg cylinders at hole doping concentration δ = 12.5%. We reveal a delicate interplay between superconductivity and charge density wave and spin density wave orders tunable via next-nearest neighbor hopping t′. For finite t′, the ground state is consistent with a Luther-Emery liquid with power-law superconducting and charge density wave correlations associated with half-filled charge stripes. In contrast, for t′ = 0, superconducting correlations fall off exponentially, whereas charge density and spin density modulations are dominant. Our results indicate that a route to robust long-range superconductivity involves destabilizing insulating charge stripes in the doped Hubbard model.

scholarly journals Energy Scale of the Charge Density Wave in Cuprate Superconductors

Proceedings ◽  
2019 ◽  
Vol 26 (1) ◽  
pp. 20
Author(s):  
Sacuto ◽  
Loret ◽  
Auvray ◽  
Civelli ◽  
Indranil ◽  
...  
Keyword(s):  
High Temperature ◽  
Charge Density ◽  
Charge Density Wave ◽  
Cuprate Superconductors ◽  
High Temperature Superconductors ◽  
Density Wave ◽  
Energy Scale ◽  
Hole Doping ◽  
Wide Range

The cuprate high temperature superconductors develop spontaneous charge density wave(CDW) order below a temperature TCDW and over a wide range of hole doping (p). [...]

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