Collective Infrared Excitation in LuB12 Cage-Glass

Gorshunov, B. P.; Жукова, Е. С.; Komandin, G. A.; Torgashev, V. I.; Muratov, A. V.; Aleshchenko, Yu. A.; Demishev, S. V.; Shitsevalova, N.; Филипов, В. Б.; Sluchanko, N. E.

doi:10.1134/s0021364018020029

Cited by 19 publications

(19 citation statements)

References 21 publications

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“…1b). Strong coupling of these Lu rattling modes located at 110 cm -1 (~14 meV) [34] and the JT active vibrations of boron are the origin of both lattice instability and the emergence of the collective excitations in the optical spectra of LuB 12 [35].…”

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confidence: 99%

Hall effect and symmetry breaking in the nonmagnetic metal LuB12 with dynamic charge stripes

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A comprehensive study of magnetoresistance and Hall effect has been performed for the set of the single crystals of non-magnetic metal LuB 12 with the Jahn-Teller instability of the boron cage and dynamic charge stripes forming along <110> direction. Anomalous positive contribution to Hall effect for particular direction of magnetic field H//[001] is found in the single crystals of LuB 12 of the highest quality. This contribution arising at T~ 150 K is shown to increase drastically when approaching the disordered ground state below 60 K. The Hall effect anomaly is shown to appear in combination with the peak of magnetoresistance. The various scenarios allowing for the topology of Fermi surface, anisotropy of relaxation time for charge carriers and the filamentary structure of fluctuating charge stripes are proposed to explain the features of magnetotransport in this metal with inhomogeneous distribution of electron density.The origin of SdH oscillations, which are observed in this non-equilibrium metal with electron phase separation and strong charge carrier scattering, is discussed.

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confidence: 99%

Hall effect and symmetry breaking in the nonmagnetic metal LuB12 with dynamic charge stripes

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“…It is worth noting that all these high borides are characterized by small enough residual resistivity values located in the range 0.01-50 Ohm•cm and their conduction band width is about 1.6-2 eV (see e.g. [28], [38], [39], [65], [86]), so the pseudogap may be considered as a merit of disorder and anharmonicity in these good metals.…”

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confidence: 99%

“…Indeed, inelastic neutron scattering studies of the phonon spectra in LuB 12 and ZrB 12 have detected noticeable, but not dramatic changes in the position of almost dispersion-less quasi-local mode (15 meV and 17.5 meV, correspondingly [29]), which was proposed to be responsible for Cooper pairing. Only a moderate difference in electron density of states (DOS) of these two compounds is caused by filling the wide enough conduction band (~1.62 eV, [28], [38], [39]) when Lu 3+ion is changed to Zr 4+ in the RB 12 unit cell, resulting to elevation by about 0.3-0.4 eV of the Fermi level E F for ZrB 12 in comparison with LuB 12 [35], [40]. An evidence for the formation of nodes in the superconducting gap of Zr-rich Lu x Zr 1-x B 12 dodecaborides was found in [41] and, then, a s+d-to-s-wave crossover was observed using these SR measurements.…”

Section: Introductionmentioning

confidence: 99%

Inhomogeneous superconductivity in LuxZr1−xB12 dodecaborides with dynamic charge stripes

et al. 2021

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We have studied the normal and superconductive state characteristics (resistivity, Hall coefficient, heat capacity and magnetization) of model strongly correlated electronic systems Lu x Zr 1-x B 12 with cooperative Jahn-Teller instability of the boron rigid cage and with dynamic charge stripes. It was found that these metals are s-wave dirty limit superconductors with a small mean free path of charge carriers l = 5 -140 Å and with a Cooper pair size changing nonmonotonously in the range 450 -4000 Å. The parent ZrB 12 and LuB 12 borides are type-I superconductors, and Zr to Lu substitution induces a type-I -type-II phase transition providing a variation of the Ginzburg-Landau-Maki parameter in the limits 0.65   1,2  6. We argue in favor of the two-band scenario of superconductivity in Lu x Zr 1-x B 12 with gap values Δ 1 ~ 14 K and Δ 2 ~ 6 -8 K, with pairing corresponding to strong coupling limit ( e-ph ~ 1) in the upper band, and to weak coupling ( e-ph ~ 0.1 -0.4) in the lower one. A pseudogap Δ ps-gap ~ 60 -110 K is observed in Lu x Zr 1-x B 12 above T c . We discuss also the possibility of anisotropic single-band superconductivity with stripe-induced both pair-breaking and anisotropy, and analyze the origin of unique enhanced surface superconductivity detected in these model compounds.

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“…In recent studies of the charge transport, magnetic and thermal properties and fine details of fcc crystal structure of non-magnetic LuB 12 , antiferromagnetic HoB 12 -TmB 12 compounds and solid solutions Tm 1-x Yb x B 12 , it was established that the cooperative Jahn-Teller dynamics of B 12 clusters should be considered as one of the main factors responsible for a strong renormalization of the quasiparticle spectra, electron phase separation and the symmetry breaking in RE dodecaborides [14][15][16][17][18]. It was suggested that the ferrodistortive effect in the boron sublattice generates both collective modes (overdamped oscillators in the frequency range 250-1000 cm -1 [17][18] in the dynamic conductivity spectra of each of the metallic RB 12 compounds and rattling modes, -quasi-local vibrations of heavy rare earth ions embedded in the oversized B 24 cavities.…”

Section: Introductionmentioning

confidence: 99%

“…Accordingly, these overlap alterations along the rhombic (of [110]-type) axes are responsible for the modulation of the conduction electron density with a frequency ~2•10 11 Hz [17] providing the emergence of dynamic charge stripes which are the feature of a nanoscale electron instability and electron phase separation. It was argued in [17][18] that non-equilibrium charge carriers dominated in RE dodecaborides taking 50-70% from the total number of conduction electrons. These hot electrons cannot participate in the indirect exchange (RKKY interaction) between the RE magnetic moments.…”

Section: Introductionmentioning

confidence: 99%

Crystal-field potential and short-range order effects in inelastic neutron scattering, magnetization, and heat capacity of the cage-glass compound HoB12

et al. 2021

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The strongly correlated system Ho 11 B 12 with boron sublattice Jahn-Teller instability and nanoscale electronic phase separation (dynamic charge stripes) was studied in detail by inelastic neutron scattering (INS), magnetometry and heat capacity measurements at temperatures in the range 3-300 K. From the analysis of registered INS spectra, we determined parameters of the cubic crystal field at holmium sites, B 4 =-0.333 meV and B 6 = -2.003 meV (in Stevens notations), with an unconventional large ratio B 6 /B 4 pointing on the dominant role of conduction electrons in the formation of a crystal field potential. The molecular field in the antiferromagnetic state, B loc = (1.75± 0.1) T has been directly determined from the INS spectra together with short-range order effects detected in the paramagnetic state. A comparison of measured magnetization in diluted Lu 0.99 Ho 0.01 B 12 and concentrated HoB 12 single crystals showed a strong suppression of Ho magnetic moments by antiferromagnetic exchange interactions in holmium dodecaboride. To account explicitly for the short-range antiferromagnetic correlations, a self-consistent holmium dimer model was developed that allowed us to reproduce successfully field and temperature variations of the magnetization and heat capacity in the cage-glass phase of HoB 12 in external magnetic fields.

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Collective Infrared Excitation in LuB12 Cage-Glass

Cited by 19 publications

References 21 publications

Hall effect and symmetry breaking in the nonmagnetic metal LuB12 with dynamic charge stripes

Hall effect and symmetry breaking in the nonmagnetic metal LuB12 with dynamic charge stripes

Inhomogeneous superconductivity in LuxZr1−xB12 dodecaborides with dynamic charge stripes

Crystal-field potential and short-range order effects in inelastic neutron scattering, magnetization, and heat capacity of the cage-glass compound HoB12

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