Multiple regions of quantum criticality in YbAgGe

Schmiedeshoff, G. M.; Mun, Eundeok; Lounsbury, Amanda W.; Tracy, S. J.; Palm, E. C.; Hannahs, S. T.; Park, J.-H.; Murphy, T. P.; Bud’ko, Sergey L.; Canfield, Paul C.

doi:10.1103/physrevb.83.180408

Cited by 39 publications

(52 citation statements)

References 35 publications

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“…As already mentioned, a smooth suppression of the AFM order by field at B < 3 T does no lead to a single QCP as observed in prototypical heavy-fermion systems, e.g., YbRh 2 Si 2 24 . In parallel to the case of YbAgGe 8,11 , this is believed to be a consequence of geometrical frustration of local magnetic moments forming the quasi-Kagome lattice. The sequence of the multiple phase boundaries is observed in a very confined critical phase space in the vicinity of a magnetic dome (phase C), i.e., between B = 3 and 5 T. This is to be compared to the T -B phase diagram composed of a similar sequence of transitions in, e.g., YbAgGe 8 and CeAgBi 2 23 , where the metamagnetic transitions are spread over a considerably large phase space.…”

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

“…In parallel to the case of YbAgGe 8,11 , this is believed to be a consequence of geometrical frustration of local magnetic moments forming the quasi-Kagome lattice. The sequence of the multiple phase boundaries is observed in a very confined critical phase space in the vicinity of a magnetic dome (phase C), i.e., between B = 3 and 5 T. This is to be compared to the T -B phase diagram composed of a similar sequence of transitions in, e.g., YbAgGe 8 and CeAgBi 2 23 , where the metamagnetic transitions are spread over a considerably large phase space. Following previous neutron scattering experiments 16 , the large phase space at the low-temperature, low-field corner (phase A) is an incommensurate AFM phase associated with two-thirds Ce moments at sites Ce(1) and Ce(3), though the incommensurate component of the wave vector has been found to be slightly field dependent 25 .…”

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

“…Geometrical frustration has been discussed as having a profound influence to the ground-state physics of this compound series. For example, a complex temperature-field (T -B) phase diagram was found in a Yb-based homologue, YbAgGe, with multiple magnetic phases and a nFL regime that was ascribed to quantum bicriticality in the presence of significant frustration 8,11 . Moreover, it was demonstrated for CeRhSn by thermal expansion measurements that the geometrical frustration in the ab plane is responsible for its zero-field quantum criticality 12 .…”

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

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Temperature-field phase diagram of geometrically frustrated CePdAl

Zhao

Zhang

et al. 2016

Phys. Rev. B

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From the electrical resistivity and ac susceptibility measurements down to T = 40 mK, a rich temperature-field phase diagram has been constructed for the geometrically frustrated heavy-fermion compound CePdAl. In the limit of zero temperature, the field-induced suppression of the antiferromagnetism in this compound results in a sequence of phase transitions/corssovers, rather than a single critical point, in a critical region of field 3−5 T. In the lowest temperature region, a powerlaw description of the temperature-dependent resistivity yields A·T n with n>2 for all applied fields. However, a quadratic-in-temperature resistivity term can be extracted when assuming an additional electron scattering channel from magnon-like excitations, with A diverging upon approaching the critical regime. Our observations suggest CePdAl to be a new playground for exotic physics arising from the competition between Kondo screening and geometrical frustration. PACS numbers: Valid PACS appear hereWhile identifying the magnetic ground state of a geometrically frustrated insulating spin system continues to be an intriguing topic in condensed matter physics 1 , frustrated metallic magnets with Kondo screening emerge as a new playground for exotic physics 2-5 . The ground state of a Kondo lattice composed of localized f electrons and a surrounding Fermi sea in the absence of geometrical frustration has been well described by Doniach's phase diagram 6 . At one side of an appropriate external tuning parameter such as pressure, the indirect exchange interaction between f sites, i.e., the Ruderman-KittelKasuya-Yosida (RKKY) interaction tends to drive the system to be magnetically, usually antiferromagnetically, ordered. At the other, the Kondo effect prevails and screens the magnetic moments of f electrons, giving rise to a Landau Fermi liquid (LFL) with enhanced mass of composite quasiparticles. If the magnetic order disappears in a smooth way as a function of the tuning parameter, a quantum critical point (QCP) ensues. In the vicinity of a QCP where quantum fluctuations are dominating over thermal fluctuations, interesting physics like unconventional superconductivity and non-Fermi liquid (nFL) phenomena may arise 7 . The presence of geometrical frustration may lead to additional quantum fluctuations of local moments, adding to the delicate competition between the Kondo effect and RKKY interaction. Theoretically, a global phase diagram which goes beyond the single QCP in Doniach's phase diagram has been proposed for such a system, with quantum spin liquid, magnetic order, LFL and nFL behavior in different parts of phase space 3,5 . Experimentally, however, this topic is largely unexplored, partly due to the lack of appropriate frustrated Kondo systems.A Kondo-lattice series coming into attention in this context crystallizes in the hexagonal ZrNiAl-type structure with space group P62m 8,9 . There, the rare-earth atoms occupying the Zr site form a quasi-Kagome lattice with corner-sharing equilateral triangles in the abplane 10 . Geometric...

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Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

Section: Pacs Numbers: Valid Pacs Appear Herementioning

confidence: 99%

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Temperature-field phase diagram of geometrically frustrated CePdAl

Zhao

Zhang

et al. 2016

Phys. Rev. B

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“…At low temperatures T & 4 K, antiferromagnetic correlations develop, reflected in a maximum in the susceptibility ab . Finally, a sharp first-order transition into a magnetically ordered phase occurs at T N ¼ 0:65 K [9,10,12,14,15]. The large factor f ¼ jÂ ab j=T N ¼ 23 indicates frustrated interaction between magnetic moments.…”

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Quantum Bicriticality in the Heavy-Fermion Metamagnet YbAgGe

et al. 2013

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Bicritical points, at which two distinct symmetry-broken phases become simultaneously unstable, are typical for spin-flop metamagnetism. Interestingly, the heavy-fermion compound YbAgGe also possesses such a bicritical point (BCP) with a low temperature T(BCP)≈0.3 K at a magnetic field of μH(BCP)≈4.5 T. In its vicinity, YbAgGe exhibits anomalous behavior that we attribute to the influence of a quantum bicritical point that is close in parameter space yet can be reached by tuning T(BCP) further to zero. Using high-resolution measurements of the magnetocaloric effect, we demonstrate that the magnetic Grüneisen parameter ΓH indeed both changes sign and diverges as required for quantum criticality. Moreover, ΓH displays a characteristic scaling behavior but only on the low-field side H≲H(BCP), indicating a pronounced asymmetry with respect to the critical field. We speculate that the small value of T(BCP) is related to the geometric frustration of the Kondo lattice of YbAgGe.

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“…The stoichiometric compound YbAgGe [15] also exhibits an extended region of NFL behavior with applied magnetic field [16,17]. However, accessing the ordered magnetic state close to the QCP and studying the evolution of the microscopic magnetic correlations in the NFL regime is complicated by either the requirement of attaining extremely low temperatures (T N ≈ 0.05 K) for YbRh 2 Si 2 [18,19] or by a complex series of magnetic transitions with applied field for YbAgGe [17].…”

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Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

et al. 2014

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We report results from neutron scattering experiments on single crystals of YbBiPt that demonstrate antiferromagnetic order characterized by a propagation vector, τAFM = ( 1 2 1 2 1 2 ), and ordered moments that align along the [1 1 1] direction of the cubic unit cell. We describe the scattering in terms of a two-Gaussian peak fit, which consists of a narrower component that appears below TN ≈ 0.4 K and corresponds to a magnetic correlation length of ξn ≈ 80 Å, and a broad component that persists up to T * ≈ 0.7 K and corresponds to antiferromagnetic correlations extending over ξ b ≈ 20 Å. Our results illustrate the fragile magnetic order present in YbBiPt and provide a path forward for microscopic investigations of the ground states and fluctuations associated with the purported quantum critical point in this heavy-fermion compound.

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Multiple regions of quantum criticality in YbAgGe

Cited by 39 publications

References 35 publications

Temperature-field phase diagram of geometrically frustrated CePdAl

Temperature-field phase diagram of geometrically frustrated CePdAl

Quantum Bicriticality in the Heavy-Fermion Metamagnet YbAgGe

Fragile antiferromagnetism in the heavy-fermion compound YbBiPt

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