New phase diagram for (U,Th)<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Be</mml:mi></mml:mrow><mml:mrow><mml:mn>13</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>: A muon-spin-resonance and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">H</mml:mi></mml:mrow><mml:mrow><mml:mi mathvariant="italic">C</mml:mi><mml:mn>1</mml:mn></mml:m

Heffner, R. H.; Smith, J. L.; Willis, J. O.; Birrer, P.; Baines, C.; Gygax, F. N.; Hitti, B.; Lippelt, E.; Ott, H. R.; Schenck, A.; Knetsch, E.A.; Mydosh, J. A.; MacLaughlin, D. E.

doi:10.1103/physrevlett.65.2816

Cited by 191 publications

(118 citation statements)

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“…1(a)] [13,14]. It has been reported that there exist four phases (A, B, C, and D) in its SC state, according to the previous µSR [16] and thermalexpansion [24] experiments using polycrystalline samples. The SC transition temperature T c is non-monotonic as a function of the Th concentration x in U 1−x Th x Be 13 , and exhibits a sharp minimum near x = 0.02.…”

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confidence: 86%

“…Below T c1 , another phase transition accompanied by a large heat-capacity jump occurs at T c2 in a narrow range of 0.019< x <0.045 [14,16]. Interestingly, only for this x region, weak magnetic correlations have been observed in zero-field µSR measurements [16]. The previous thermal-expansion study [24] claimed that the low-temperature ("T L ") anomaly appearing below T c for 0 ≤ x < 0.02, which can be connected to the "B * anomaly" observed in pure UBe 13 [24,26,27], is a precursor of the transition at T c2 .…”

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confidence: 99%

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Quasiparticle excitations and evidence for superconducting double transitions in monocrystalline U0.97Th0.03Be13

et al. 2017

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Superconducting (SC) gap symmetry and magnetic response of cubic U0.97Th0.03Be13 are studied by means of high-precision heat-capacity and dc magnetization measurements using a single crystal, in order to address the long-standing question of its second phase transition at Tc2 in the SC state below Tc1. The absence (presence) of an anomaly at Tc2 in the field-cooling (zero-field-cooling) magnetization indicates that this transition is between two different SC states. There is a qualitative difference in the field variation of the transition temperatures; Tc2(H) is isotropic whereas Tc1(H) exhibits a weak anisotropy between [001] and [111] directions. In the low temperature phase below Tc2(H), the angle-resolved heat-capacity C(T, H, φ) reveals that the gap is fully opened over the Fermi surface, narrowing down the possible gap symmetry.The nature of superconductivity in heavy-fermion compounds is of primary importance because an unconventional pairing mechanism is generally expected to occur due to strong electron correlation between heavy quasiparticles. The discovery of heavy-fermion superconductivity in UBe 13 [1] triggered exploration of unconventional pairing mechanism in 5f actinide compounds, and subsequently two uranium compounds, UPt 3 [2] and URu 2 Si 2 [3, 4], were found to show superconductivity. These U-based heavy-fermion superconductors have attracted considerable interest because of their unusual superconducting (SC) and normal-state properties. Among these, superconductivity in UBe 13 is highly enigmatic; it emerges from a strongly non-Fermi-liquid state with a large resistivity (ρ ∼ 150 µΩcm). Also unusual is the temperature variation of the upper critical field H c2 : an enormous initial slope −(dH c2 /dT ) Tc ∼ 42 T/K and an apparent absence of a Pauli paramagnetic limiting at low temperatures [5]. Extensive studies have been made to elucidate the SC gap symmetry [6,7], with an expectation of an oddparity pairing in this compound [8][9][10][11]. Recently, it has been found quite unexpectedly that nodal quasiparticle excitations in UBe 13 are absent as revealed by low-T angle-resolved heatcapacity measurements for a single crystalline sample [12].A long-standing mystery regarding UBe 13 is the occurrence of a second phase transitions in the SC state when a small amount of Th is substituted for U [ Fig. 1(a)] [13,14]. It has been reported that there exist four phases (A, B, C, and D) in its SC state, according to the previous µSR [16] and thermalexpansion [24] experiments using polycrystalline samples. The SC transition temperature T c is non-monotonic as a function of the Th concentration x in U 1−x Th x Be 13 , and exhibits a sharp minimum near x = 0.02. Further doping of Th results in an increase of the bulk SC transition temperature (T c1 ), reaching a local maximum at x ∼ 0.03 [13]. Below T c1 , another phase transition accompanied by a large heat-capacity jump occurs at T c2 in a narrow range of 0.019< x <0.045 [14,16]. Interestingly, only for this x region, weak magnetic correlations hav...

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Quasiparticle excitations and evidence for superconducting double transitions in monocrystalline U0.97Th0.03Be13

et al. 2017

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“…In zero field, Λ shows a gradual increase with decreasing temperature even in the normal state, in contrast to other HF superconductors [19,20,22]. The H LF dependence of Λ shown in Fig.…”

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confidence: 99%

“…TRS-broken SC states are quite rare, since an unambiguous observation of such fields has been made only in Sr 2 RuO 4 [18]. In the low-T phase of Th-doped UBe 13 , the possibility of a magnetic phase coexisting with the SC state cannot be ruled out [19] and, on an observation in UPt 3 [20], doubt has been cast later [21,22].In this Letter, we report on ZF-µSR measurements for …”

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confidence: 99%

Time-Reversal Symmetry-Breaking Superconductivity in Heavy-FermionPrOs4Sb12Detec

et al. 2003

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We report on muon spin relaxation measurements of the 4f 2 -based heavy-fermion superconductor filled-skutterudite PrOs4Sb12. The results reveal the spontaneous appearance of static internal magnetic fields below the superconducting transition temperature, providing unambiguous evidence for the breaking of time-reversal symmetry in the superconducting state. A discussion is made on which of the spin or orbital component of Cooper pairs carries a nonzero momentum.PACS numbers: 74.70. Tx, 76.75.+i, 74.70.Dd, 74.25.Ha Many unconventional superconducting (SC) states, as in Ce-and U-based heavy-fermion (HF) compounds or high-T c cuprates, appear in close proximity to magnetic instabilities when a certain parameter (pressure, atomic doping, or oxygen content) is varied [1,2,3]. This fact strongly suggests that the attractive interactions binding electrons into Cooper pairs are mediated by magnetic moment fluctuations. As another possible pairing glue, fluctuations of quadrupole moments-distorted shapes of the electronic clouds of ions, are theoretically considered to be possible [4,5]. An interesting question to be addressed is what is the nature of superconductivity in such a system. For this study, Pr-based compounds with a 4f 2 configuration are likely candidates, since nonmagnetic but quadrupolar active low-energy levels can be realized due to the crystalline-electric-field (CEF) effect; in 5f systems, CEF levels are less clear due to the tendency to be itinerant.One promising candidate material for this study is the recently found superconductor PrOs 4 Sb 12 [6], which is to date the only known Pr-based HF superconductor, with a superconducting transition temperature of 1.82 K (hereafter referred to as T c1 ). The estimated electronic specific heat coefficient γ = 350 − 700 mJ/K 2 mol [6,7] and the enhanced cyclotron-effective masses [8] reflect the existence of strong electron correlations. Specific heat (C), magnetic susceptibility (χ), and inelastic neutron studies provide evidence that PrOs 4 Sb 12 has a nonmagnetic ground state and a magnetic triplet excited state separated by ∆E CEF /k B = 8 K [7,9], which is 5 times larger than T c1 . In the temperature-versus-magneticfield (T -vs-H) phase diagram, a field-induced ordered phase (µ 0 H 4 T) [9] appears close to the superconducting phase (the upper critical field µ 0 H c2 = 2.2 T). It was recently proven to be an antiferro-quadrupolar ordered phase by elastic neutron scattering measurements [10]. This fact strongly indicates that quantum quadrupole fluctuations of the Pr ions play an important role in realizing the HF superconductivity in PrOs 4 Sb 12 , considering that the T -vs-H phase diagram is analogous to those for the HF and cuprate systems, where a magnetically ordered phase exists close to the SC phase in the T -vs-pressure, -atomic-doping, or -oxygen-content phase diagram. This scenario is further supported by the enhanced T c1 compared to T c = 0.74 K for a 4f 0 reference compound LaOs 4 Sb 12 [8,11].The remarkable unconventional SC properties ...

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“…8. Microscopic measurements using the μSR technique [33] indicate that in the superconducting phase denoted as L, superconductivity either coexists with ordered magnetic moments of the order of 10 -2 µ$/U or that the superconducting order parameter carriers a magnetic component. Model calculations based on a Ginzburg-Landau-type analysis [34] indicate that the second possibility may indeed be realized.…”

Section: U1_x Thxbe13_ Bymentioning

confidence: 99%

Aspects of Magnetism in Heavy-Electron Metals

Ott

1994

Acta Phys. Pol. A

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For some time it was believed that heavy-mass electrons at low temperatures, in special rare-earth and actinide compounds, were due to a particular suppression of magnetic order in these materials. Various experiments reveal, however, that magnetic order may occur from a heavy-electron state and that also a heavy-electron state may develop in the presence of a magnetically-ordered matrix. Even in materials with no sign of a cooperative phase transition, microscopic experimental probes give evidence for strong magnetic correlations, involving only very tiny (< 10 -1 μn) ordered moments, however. All these experimental observations indicate that the heavy-electron state cannot always be regarded as a simple Fermi liquid in the usual sense. Various interactions of similar strength need to be considered. It is suggested that the balance of these interactions may lead to electronic inhomogeneities in k space. Both in magnetically-ordered or superconducting systems, unexpected electronic degrees of freedom appear to exist. In other cases experimental observations suggest magnetic inhomogeneities in real space which are not simply due to chemical inhomogeneities. Different examples of these various possibilities are demonstrated and discussed.

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New phase diagram for (U,Th)Be13: A muon-spin-resonance andHC1

Cited by 191 publications

References 17 publications

Quasiparticle excitations and evidence for superconducting double transitions in monocrystalline U0.97Th0.03Be13

Quasiparticle excitations and evidence for superconducting double transitions in monocrystalline U0.97Th0.03Be13

Time-Reversal Symmetry-Breaking Superconductivity in Heavy-FermionPrOs4Sb12Detec

Aspects of Magnetism in Heavy-Electron Metals

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