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Storchak, Vyacheslav G.; Brewer, J. H.; Arseneau, Donald J.; Stubbs, Scott L.; Parfenov, Oleg E.; Eshchenko, D. G.; Буш, А. А.

doi:10.1103/physrevb.79.220406

Cited by 14 publications

(15 citation statements)

References 32 publications

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“…The temperature dependence of the corresponding line widths (relaxation rates) clearly reflects this difference: at high temperature the line width of the stable eigenstate (higher frequency line) is much less than that of the other state (Figure 2 and Figure 6). Similar asymmetric distributions of the spectral weight between the two lines of the SP doublet are detected in magnetic semiconductors and insulators where the SP is found to be static 60,[62][63][64]77 .…”

Section: Figuresupporting

confidence: 59%

“…Although the possibility of SP formation in AFM and PM states has long been anticipated [46][47][48]52,53 and experimentally established [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73]77,85,86 in a great variety of materials by many different techniques, its existence would seem to be incompatible with the FM state. The exchange contribution to SP stabilization amounts to the difference between the PM disorder (or AFM order) of the host and the FM order within the SP; in a fully saturated FM state the exchange contribution to the localization would be negligible, as the lattice spins are already aligned.…”

Section: Figurementioning

confidence: 99%

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Spin-polaron band in the ferromagnetic heavy-fermion superconductor UGe₂

Storchak¹,

Brewer²,

Eshchenko³

et al. 2014

J. Phys.: Conf. Ser.

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In strongly correlated materials, cooperative behaviour of the electrons causes a variety of quantum ordered states that may, in some cases, coexist 1-3 . It has long been believed, however, that such coexistence among ferromagnetic ordering, superconductivity and heavy-fermion behaviour is impossible, as the first supports parallel spin alignment while the conventional understanding of the latter two phenomena assumes spin-singlet or antiparallel spins. This understanding has recently been challenged by an increasing number of observations in uranium intermetallic systems (UGe 2 , URhGe, UIr and UCoGe) 4-7 in which superconductivity is found within a ferromagnetic state and, more fundamentally, both ordering phenomena are exhibited by the same set of comparatively heavy 5f electrons. Since the coexistence of superconductivity and ferromagnetism is at odds with the standard theory of phonon-mediated spin-singlet superconductivity, it requires an alternative pairing mechanism, in which electrons are bound into spin-triplet pairs by spin fluctuations 8,9 . Within the heavy-fermion scenario, this alternative mechanism necessarily assumes that the magnetism has a band character and that said band forms from heavy quasiparticles composed of f electrons. This band is expected to be responsible for all three remarkable phenomenaheavy-fermion behaviour, ferromagnetism and superconductivity although its nature and the nature of those heavy quasiparticles still remains unclear. Here we report spectroscopic evidence (from high-field muon spin rotation measurements) for the formation in UGe 2 of subnanometer-sized spin polarons whose dynamics we follow into the paramagnetic and ferromagnetic phases. These spin polarons behave as heavy carriers and thus may serve as heavy quasiparticles made of 5f electrons; once coherence is established, they form a narrow spin-polaron band which thus provides a natural reconciliation of itinerant ferromagnetism with spin-triplet superconductivity and heavy-fermion behaviour.Within the BCS theory of superconductivity (SC), it became clear long ago 10 that pairing of electrons in the spin-singlet state is effectively destroyed by an exchange mechanism arising from strong Coulomb interactions between the valence electrons. In a ferromagnetically (FM) ordered state, this exchange interaction tends to align the spins of electrons within a Cooper pair in parallel, thereby effectively preventing the pairing. Likewise, within the standard heavy-fermion (HF) approach, the Kondo effect

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Section: Figuresupporting

confidence: 59%

Section: Figurementioning

confidence: 99%

Spin-polaron band in the ferromagnetic heavy-fermion superconductor UGe₂

Storchak¹,

Brewer²,

Eshchenko³

et al. 2014

J. Phys.: Conf. Ser.

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“…The doublet in figures 1 and 2 may originate from a coupled m +e spin system in high transverse magnetic field [19,20,22,[26][27][28][29][30][31]: the two lines correspond to two muon spin-flip transitions between states with the electron spin orientation fixed, the splitting between them being determined by the muon-electron hyperfine interaction A [26,27]. The temperature behaviour of lines with one line going up in frequency and the other going down as temperature decreases is often a signature of a muon-electron bound state [20,22].…”

Section: Muon Spin Rotation Studiesmentioning

confidence: 99%

“…Such SP states have been previously invoked to explain μ + SR spectra in strongly correlated insulators [28,38], semiconductors [26,27,31] and metals [29,30]. The latter reference initiated a debate on SP formation in MnSi [39,40].…”

Section: Muon Spin Rotation Studiesmentioning

confidence: 99%

“…In a PM, strong spin exchange with the environment [20,22] would result in rapid spin fluctuations of the SP electron, averaging the hyperfine interaction to zero, thereby resulting in a collapse of the doublet into a single line at n m (see [26,41,42] for details) unless the SP spin is decoupled from the local spins [26,27,29,42]. Such decoupling is possible in high B when the Zeeman energy of  exceeds an exchange interaction J between local spins-this is the case in magnetic insulators where the SP doublet is detected up to very high temperature [19,[26][27][28]. In metals, RKKY interactions make J much stronger, so that decoupling requires B strengths that are inaccessible in the current experiment.…”

Section: Muon Spin Rotation Studiesmentioning

confidence: 99%

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Spin gap in heavy fermion compound UBe₁₃

et al. 2016

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Heavy fermion (HF) compounds are well known for their unique properties, such as narrow bandwidths, loss of coherence in a metal, non-Fermi-liquid behaviour, unconventional superconductivity, huge magnetoresistance etc. While these materials have been known since the 1970s, there is still considerable uncertainty regarding the fundamental mechanisms responsible for some of these features. Here we report transverse-field muon spin rotation (μ + SR) experiments on the canonical HF compound UBe 13 in the temperature range from 0.025 to 300 K and in magnetic fields up to 7 T. The μ + SR spectra exhibit a sharp anomaly at 180 K. We present a simple explanation of the experimental findings identifying this anomaly with a gap in the spin excitation spectrum of f-electrons opening near 180 K. It is consistent with anomalies discovered in heat capacity, NMR and optical conductivity measurements of UBe 13 , as well as with the new resistivity data presented here. The proposed physical picture may explain several long-standing mysteries of UBe 13 (as well as other HF systems).

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