Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2

Tonegawa, S.; Kasahara, S.; Fukuda, Tatsuo; Sugimoto, Kunihisa; Yasuda, Naohiko; Tsuruhara, Y.; Watanabe, Daiki; Mizukami, Y.; Haga, Yoshinori; Matsuda, Tatsuma D.; Yamamoto, Etsuji; Ōnuki, Yoshichika; Ikeda, Hiroaki; Matsuda, Yuji; Shibauchi, T.

doi:10.1038/ncomms5188

Cited by 77 publications

(143 citation statements)

References 41 publications

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“…Quantitative calculations on the lattice dynamics based on precise electronic ordering at T 0 would be necessary to distinguish which effects would be sizable. Recently, orthorhombic distortion upon entering the HO has been measured by X-ray scattering by Tonegawa et al 29 in disagreement with results by Amitsuka et al 62 . We do not observe any splitting or broadening of the phonons measured by Raman scattering or by optical conductivity measurements nor signs of the effect of the orthorhombic distortion on the in-plane acoustic phonons.…”

Section: General Discussion and Conclusioncontrasting

confidence: 48%

“…Four-fold symmetry breaking and even orthorhombic distortion upon entering the HO state have been reported by various experiments [27][28][29] . However, the symmetry broken here is B 2g , i.e.…”

Section: Resultsmentioning

confidence: 99%

“…It is well admitted that a Brillouin zone folding from a body center tetragonal (bct) to a simple tetragonal (st) phase occurs upon entering the HO state 16,25,26 . Recently, various experiments have identified a four-fold symmetry breaking upon entering the HO state 27,28 and orthorhombic static lattice distortion has been reported by Tonegawa et al 29 .…”

Section: Introductionmentioning

confidence: 99%

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Lattice dynamics of the heavy-fermion compoundURu2Si2

et al. 2015

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We report a comprehensive investigation of the lattice dynamics of URu2Si2 as a function of temperature using Raman scattering, optical conductivity and inelastic neutron scattering measurements as well as theoretical ab initio calculations. The main effects on the optical phonon modes are related to Kondo physics. The B1g (Γ3 symmetry) phonon mode slightly softens below ∼100 K, in connection with the previously reported softening of the elastic constant, C11 − C12, of the same symmetry, both observations suggesting a B1g symmetry-breaking instability in the Kondo regime. Through optical conductivity, we detect clear signatures of strong electron-phonon coupling, with temperature dependent spectral weight and Fano line shape of some phonon modes. Surprisingly, the line shapes of two phonon modes, Eu(1) and A2u(2), show opposite temperature dependencies. The A2u(2) mode loses its Fano shape below 150 K, whereas the Eu(1) mode acquires it below 100 K, in the Kondo cross-over regime. This may point out to momentum-dependent Kondo physics. By inelastic neutron scattering measurements, we have drawn the full dispersion of the phonon modes between 300 K and 2 K. No remarkable temperature dependence has been obtained including through the hidden order transition. Ab initio calculations with the spin-orbit coupling are in good agreement with the data except for a few low energy branches with propagation in the (a,b) plane.

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Section: General Discussion and Conclusioncontrasting

confidence: 48%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lattice dynamics of the heavy-fermion compoundURu2Si2

et al. 2015

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“…The fact that it also hosts unconventional superconductivity makes this material even more attractive. Recent success in producing high quality specimens [5][6][7] has resulted in a surge of experimental work, including electronic Raman spectroscopy [8], elastoresistance [9], resonant ultrasound [10], Kerr rotation [11], X-ray scattering [12], and quantum oscillation measurements [13][14][15], which have provided unprecedented insight into the electronic, ordered state, and superconducting behavior. However, progress is limited by restricted access to high quality specimens, particularly due to challenges that are inherent to the mainstream growth techniques.…”

Section: Introductionmentioning

confidence: 99%

Single Crystal Growth of URu2Si2 by the Modified Bridgman Technique

et al. 2016

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Abstract:We describe a modified Bridgman growth technique to produce single crystals of the strongly correlated electron material URu 2 Si 2 and its nonmagnetic analogue ThRu 2 Si 2 . Bulk thermodynamic and electrical transport measurements show that the properties of crystals produced in this way are comparable to those previously synthesized using the Czochralski or conventional molten metal flux growth techniques. For the specimens reported here, we find residual resistivity ratios RRR = ρ 300K /ρ 0 as large as 116 and 187 for URu 2 Si 2 and ThRu 2 Si 2 , respectively.

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“…Furthermore, with entering the HO phase, the breaking of the fourfold rotational symmetry has been reported from torque experiments (21), high resolution X-ray diffraction on high quality crystals (22), and elastoresistance measurements (23). For a more detailed experimental and theoretical survey of physical properties of URu2Si2, we refer to the review article by Mydosh and Oppeneer (24).…”

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confidence: 99%

Direct bulk-sensitive probe of 5 f symmetry in URu ₂ Si ₂

Sundermann

Haverkort

Agrestini

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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The second-order phase transition into a hidden order phase in URu 2 Si 2 goes along with an order parameter that is still a mystery, despite 30 years of research. However, it is understood that the symmetry of the order parameter must be related to the symmetry of the low-lying local electronic f-states. Here, we present results of a spectroscopic technique, namely core-level nonresonant inelastic X-ray scattering (NIXS). This method allows for the measurement of local high-multipole excitations and is bulk-sensitive. The observed anisotropy of the scattering function unambiguously shows that the 5f ground-state wave function is composed mainly of the Γ 1 with majority Jz = |4 + |−4 and/or Γ 2 singlet states. The incomplete dichroism indicates the possibility that quantum states of other irreducible representation are mixed into the ground state. strongly correlated electron systems | X-ray spectroscopy | crystal-electric field | heavy fermions | hidden order I n heavy fermion rare earth or actinide compounds, the f electrons are well localized at high temperatures, but as temperature is lowered, hybridization with conduction electrons becomes increasingly effective, resulting in a more itinerant f -electron character at low temperatures. These hybridized f electrons form narrow bands and have large effective masses. Quasiparticle interaction effects in these narrow bands are responsible for the many exciting phenomena present in heavy fermion compounds: multipolar order (1), unconventional superconductivity (2), or quantum criticality (3). The hidden order phase in URu2Si2 is one example of the exotic low-temperature phases found in this material class. URu2Si2 is a tetragonal heavy fermion compound that undergoes two phase transitions, the nonmagnetic hidden order (HO) transition at THO = 17.5 K, which involves an appreciable loss of entropy, and a superconducting transition at about 1.5 K (4-7). Below the HO transition, small-ordered magnetic moments were observed in the earlier studies but were determined later to belong to a parasitic minority phase. With applied pressure (p ≥ 0.7 GPa), the HO order is replaced by an antiferromagnetic phase with large-ordered moments (so-called LMAF -phase) (8). The order parameter of the HO phase has been the subject of intense investigations for more than 30 years but, so far, has remained hidden, which has been the inspiration for its name. This second-order transition into an electronically ordered state involves a reconstruction of the Fermi surface (9, 10) and a change of quasiparticle scattering rate (11). The Fermi surfaces of the HO and high-pressure LMAF phase are very similar (12).In URu2Si2 three-energy scales have been identified: a hybridization gap of ∆ hyb ≈ 13 meV [150 K] (13) that opens below 27 K, another gap that opens in the HO phase with ∆HO ≈ 4.1 meV [50 K] in the charge (9, 10, 14, 15) as well as spin channel (16,17), and a resonance mode that appears in the HO gap at ∼ =1.6 meV [18 K], also in both channels (18)(19)(20). Furthermore, with entering ...

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Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2

Cited by 77 publications

References 41 publications

Lattice dynamics of the heavy-fermion compoundURu2Si2

Lattice dynamics of the heavy-fermion compoundURu2Si2

Single Crystal Growth of URu2Si2 by the Modified Bridgman Technique

Direct bulk-sensitive probe of 5 f symmetry in URu ₂ Si ₂

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Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2

Cited by 77 publications

References 41 publications

Lattice dynamics of the heavy-fermion compoundURu2Si2

Lattice dynamics of the heavy-fermion compoundURu2Si2

Single Crystal Growth of URu2Si2 by the Modified Bridgman Technique

Direct bulk-sensitive probe of 5 f symmetry in URu 2 Si 2

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Product

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Direct bulk-sensitive probe of 5 f symmetry in URu ₂ Si ₂