Multipolar Order and Excitations in Rare-Earth Boride Kondo Systems

Thalmeier, Peter; Akbari, Alireza; Shiina, Ryousuke

doi:10.1201/9781003146483-8

Cited by 5 publications

(5 citation statements)

References 145 publications

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“…Here one may benefit from considering the anisotropy of field-induced excitations in field space, as demonstrated recently for CeB 6 [12]. The dynamical structure factor S(Q, ω), measured by single-crystal INS in high magnetic fields applied along different crystal axes, was shown to be fairly consistent with theoretical results obtained with Holstein-Primakoff (HP) [43] and random-phase approximation (RPA) methods [13,[44][45][46].…”

Section: Introductionsupporting

confidence: 69%

“…The appearance of so-called hidden order phases in the lowtemperature magnetic phase diagrams of f -electron systems has been confronted with intensified interest in recent years [1][2][3][4][5][6]. Contrary to the conventional magnetic order composed of atomic spins, multipolar order parameters [6][7][8][9] involve both spin and orbital degrees of freedom, linked via strong spinorbit coupling, and are highly sensitive to an applied magnetic field [10][11][12][13][14]. Consequently, field-induced quantum phase transitions and quantum critical behavior emerge [15][16][17][18], showing remarkable anisotropies with respect to the magnetic field direction [14,[19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

“…An external magnetic field applied along some general direction given by the unit vector (αβ γ) selects a coherent superposition of the initially degenerate quadrupoles within each manifold as the primary order parameter, e.g. αO yz + β O zx + γO xy for Γ + 5 , which depends continuously on the field direction [13].…”

Section: Introductionmentioning

confidence: 99%

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Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

Mazza,

Portnichenko,

Avdoshenko

et al. 2022

Preprint

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Magnetically hidden order is a hypernym for electronic ordering phenomena that are visible to macroscopic thermodynamic probes but whose microscopic symmetry cannot be revealed with conventional neutron or x-ray diffraction. In a handful of f -electron systems, the ordering of odd-rank multipoles leads to order parameters with a vanishing neutron cross-section. Among them, Ce 3 Pd 20 Si 6 is known for its unique phase diagram exhibiting two distinct multipolar-ordered ground states (phases II and II ), separated by a field-driven quantum phase transition associated with a putative change in the ordered quadrupolar moment from O 0 2 to O xy . Using torque magnetometry at subkelvin temperatures, here we find another phase transition at higher fields above 12 T, which appears only for low-symmetry magnetic field directions B 11L with 1 < L ≤ 2. While the order parameter of this new phase II remains unknown, the discovery renders Ce 3 Pd 20 Si 6 a unique material with two field-driven phase transitions between distinct multipolar phases. They are both clearly manifested in the magnetic-field dependence of the field-induced (111) Bragg intensities measured with neutron scattering for B [112]. We also find from inelastic neutron scattering that the number of nondegenerate collective excitations induced by the magnetic field correlates with the number of phases in the magnetic phase diagram for the same field direction. Furthermore, the magnetic excitation spectrum suggests that the new phase II may have a different propagation vector, revealed by the minimum in the dispersion that may represent the Goldstone mode of this hidden-order phase.

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Section: Introductionsupporting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

Mazza,

Portnichenko,

Avdoshenko

et al. 2022

Preprint

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“…Interestingly, a “molecular” J eff = 3/2 Mott insulating ground state was recently proposed for GaTa 4 Se 8 , − associated with strong 5d-shell spin–orbit couplings (SOCs). Such quartet ground states are known as a playground for subtle vibronic couplings in d 1 compounds − and as source of even richer phenomenology, e.g., multipolar phases, in f-electron systems. ,− …”

mentioning

confidence: 99%

How Correlations and Spin–Orbit Coupling Work within Extended Orbitals of Transition-Metal Tetrahedra of 4d/5d Lacunar Spinels

Petersen

Prodan

Tsurkan

et al. 2022

J. Phys. Chem. Lett.

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Spin–orbit quartet ground states are associated with rich phenomenology, ranging from multipolar phases in f1 rare-earth borides to magnetism emerging through covalency and vibronic couplings in d1 transition-metal compounds. The latter effect has been studied since the 1960s on t2g 1 octahedral ML 6 units in both molecular complexes and extended solid-state lattices. Here we analyze the J eff = 3/2 quartet ground state of larger cubane-like M 4 L 4 entities in lacunar spinels, composed of transition-metal (M) tetrahedra caged by chalcogenide ligands (L). These represent a unique platform where spin–orbit coupling acts on molecular-like, delocalized t2 orbitals. Using quantum chemical methods, we pin down the interplay of spin–orbit couplings in such a setting and many-body physics related to other molecular-like single-electron levels, both below and above the reference t2 1. We provide a different interpretation of resonant inelastic X-ray scattering data on GaTa4Se8 and, by comparing magnetic susceptibility data with calculated g factors, valuable insights into the important role of vibronic couplings.

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“…The physical properties of M B 6 hexaborides are remarkably diverse and have received persistent interest [1,2], as a thorough understanding of this peculiar family of materials could not be achieved yet. Some of its members possess properties relevant for applications, generally determined by specificities of their electronic structures: CaB 6 is a semiconductor [3], YB 6 turns superconducting for temperatures lower than 8 K [4], LaB 6 is widely used as thermionic electron emitter [5], EuB 6 displays colossal magneto-resistance [6], the heavy-fermion system Ce 1−x La x B 6 has been intensively studied in the context of multipolar phases and magnetically hidden orders [7,8], while SmB 6 is believed to host correlated topological states [9]. However, even for the seemingly simplest member of the family, CaB 6 , there are important electronic-structure features that are not at all clear, for example, the size and nature of its band gap: densityfunctional computations yield a vanishing band gap [10][11][12][13][14] while experiment indicates a gap of ∼1 eV [3].…”

Section: Introductionmentioning

confidence: 99%

Quantum chemical insights into hexaboride electronic structures: correlations within the boron p-orbital subsystem

2022

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The notion of strong electronic correlations arose in the context of d-metal oxides such as NiO but can be exemplified on systems as simple as the H2 molecule. Here we shed light on correlation effects on B62− clusters as found in MB6 hexaborides and show that the B 2p valence electrons are fairly correlated. B6-octahedron excitation energies computed for CaB6 and YbB6 agree with peak positions found by resonant inelastic x-ray scattering, providing a compelling picture for the latter. Our findings characterize these materials as very peculiar p-electron correlated systems and call for more involved many-body investigations within the whole hexaboride family, both alkaline- and rare-earth compounds, not only for N- but also (N ± 1)-states defining e. g. band gaps.

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Multipolar Order and Excitations in Rare-Earth Boride Kondo Systems

Cited by 5 publications

References 145 publications

Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

Cascade of magnetic-field-driven quantum phase transitions in Ce3Pd20Si6

How Correlations and Spin–Orbit Coupling Work within Extended Orbitals of Transition-Metal Tetrahedra of 4d/5d Lacunar Spinels

Quantum chemical insights into hexaboride electronic structures: correlations within the boron p-orbital subsystem

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