A change of the Fermi surface in UGe<sub>2</sub>across the critical pressure

Settai, Rikio; Nakashima, Miho; Araki, Shingo; Haga, Yoshinori; Kobayashi, Tatsuo; Tateiwa, Naoyuki; Yamagami, Hiroshi; Ōnuki, Yoshichika

doi:10.1088/0953-8984/14/1/104

Cited by 63 publications

(93 citation statements)

References 19 publications

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“…One central issue concerns the nature of the Fermi surface: Is it "large," encompassing both the local moments and conduction electrons as in paramagnetic heavy fermion metals (17,18), or is it "small," incorporating only conduction electrons? Measurements of the de Haas-van Alphen (dHvA) effect have suggested that the Fermi surface is small in CeRu 2 Ge 2 (14-16), and have provided evidence for Fermi surface reconstruction as a function of pressure in UGe 2 (19,20). At the same time, it is traditional to consider the heavy fermion ferromagnets as having a large Fermi surface when their relationship with unconventional superconductivity is discussed (12,13,21); an alternative form of the Fermi surface in the ordered state could give rise to a new type of superconductivity near its phase boundary.…”

Section: Fermi Surface | Itinerant Magnetism | Non-fermi Liquidmentioning

confidence: 99%

Metallic ferromagnetism in the Kondo lattice

Yamamoto

2010

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

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Metallic magnetism is both ancient and modern, occurring in such familiar settings as the lodestone in compass needles and the hard drive in computers. Surprisingly, a rigorous theoretical basis for metallic ferromagnetism is still largely missing. The Stoner approach perturbatively treats Coulomb interactions when the latter need to be large, whereas the Nagaoka approach incorporates thermodynamically negligible holes into a half-filled band. Here, we show that the ferromagnetic order of the Kondo lattice is amenable to an asymptotically exact analysis over a range of interaction parameters. In this ferromagnetic phase, the conduction electrons and local moments are strongly coupled but the Fermi surface does not enclose the latter (i.e., it is "small"). Moreover, non-Fermi-liquid behavior appears over a range of frequencies and temperatures. Our results provide the basis to understand some long-standing puzzles in the ferromagnetic heavy fermion metals, and raise the prospect for a new class of ferromagnetic quantum phase transitions. Fermi surface | itinerant magnetism | non-Fermi liquidA contemporary theme in quantum condensed matter physics concerns competing ground states and the accompanying novel excitations (1). With a plethora of different phases, magnetic heavy fermion materials should reign supreme as the prototype for competing order. So far, most of the theoretical scrutiny has focused on antiferromagnetic heavy fermions (2, 3). Nonetheless, the list of heavy fermion metals that are known to exhibit ferromagnetic order continues to grow. An early example subjected to extensive studies is CeRu 2 Ge 2 (ref. 4 and references therein). Other ferromagnetic heavy fermion metals include CePt (5), CeSi x (6), CeAgSb 2 (7), and URu 2−x Re x Si 2 at x > 0.15 (8, 9). More recently discovered materials include CeRuPO (10) and UIr 2 Zn 20 (11). Finally, systems such as UGe 2 (12) and URhGe (13) are particularly interesting because they exhibit a superconducting dome as their metallic ferromagnetism is tuned toward its border. Some fascinating and general questions have emerged (14,15,16), yet they have hardly been addressed theoretically. One central issue concerns the nature of the Fermi surface: Is it "large," encompassing both the local moments and conduction electrons as in paramagnetic heavy fermion metals (17, 18), or is it "small," incorporating only conduction electrons? Measurements of the de Haas-van Alphen (dHvA) effect have suggested that the Fermi surface is small in CeRu 2 Ge 2 (14-16), and have provided evidence for Fermi surface reconstruction as a function of pressure in UGe 2 (19,20). At the same time, it is traditional to consider the heavy fermion ferromagnets as having a large Fermi surface when their relationship with unconventional superconductivity is discussed (12,13,21); an alternative form of the Fermi surface in the ordered state could give rise to a new type of superconductivity near its phase boundary. All these point to the importance of theoretically understanding the ferromagnet...

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Section: Fermi Surface | Itinerant Magnetism | Non-fermi Liquidmentioning

confidence: 99%

Metallic ferromagnetism in the Kondo lattice

Yamamoto

2010

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

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“…[76][77][78] The dHvA experiments under pressure indicate that the corresponding dHvA branches are clearly observed up to P Ã c (in the strongly polarized phase) but are scarcely seen in the pressure region form P Ã c to P c (in the weakly polarized phase). 77,78) This is mainly due to an extremely large cyclotron mass of conduction electrons in the weakly polarized phase, which is expected to be about 100m 0 from the specific heat data under pressure. It is, however, remarkable that new dHvA branches with large cyclotron masses m Ã c ¼ 60m 0 appear clearly in the paramagnetic region, P > P c , and then the conduction electrons are strongly correlated.…”

Section: 70)mentioning

confidence: 99%

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

et al. 2004

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We present recent advances in the magnetism and superconductivity of rare earth and uranium compounds. Heavy fermions are formed on the basis of the competition between the RKKY interaction and the Kondo effect in these compounds. The application of pressure to these compounds is useful to control the electronic states in the antiferromagnets CeRh 2 Si 2 and CeRhIn 5 , and the ferromagnet UGe 2 . The quadrupole interaction or the quadrupole Kondo effect is found to be responsible for heavy fermions in PrFe 4 P 12 . A rich variety of superconducting properties are demonstrated: superconductivity of CeCoIn 5 and CeRhIn 5 in the vicinity of a quantum critical point, coexistence of ferromagnetism and superconductivity in UGe 2 , and superconductivity based on the quadrupole fluctuations in PrOs 4 Sb 12 , together with the relation between the superconducting transition temperature and the quasi-two dimensionality of the electronic states.

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“…19 In the case of UCoAl, at least at low field (B ≪ B m ) and at high field (B > B M ), no major variation of the Hall constant can be pointed out. There is no evident signature of a Fermi surface reconstruction on sweeping from the PM to FM phase for P < P QCEP and from the PM to a polarized paramagnetic phase for P > P QCEP .…”

Section: Discussionmentioning

confidence: 89%

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

et al. 2013

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Hall effect measurements were performed under pressure and magnetic field up to 2.2 GPa and 16 T on a single crystal of UCoAl. At ambient pressure, the system undergoes a first order metamagnetic transition at the critical field Bm = 0.7 T from a paramagnetic ground state to a field-induced ferromagnetic state. The Hall signal is linear at low field and shows a step-like anomaly at the transition, with only little change of the Hall coefficient. The anomaly is sharpest at the temperature of the critical end point T0 = 12 K above which the first order metamagnetic transition becomes a crossover. Under pressure Bm increases and T0 decreases. The step-like anomaly in the Hall effect disappears at PM ≈ 1.3 GPa and the metamagnetic transition is not detected above the quantum critical end point (QCEP) at P∆ ≈ 1.7 GPa, Bm ≈ 7 T. Using magnetization data, we analyse our Hall resistivity data at ambient pressure in order to quantitatively account for both ordinary and anomalous contributions to the Hall effect. Under pressure, a drastic change in the field dependence of the Hall coefficient is found on crossing the QCEP. A possible Fermi surface change at Bm remains an open question.KEYWORDS: quantum critical end point, anomalous Hall effect, metamagnetism, ferromagnetism, UCoAl IntroductionThe metamagnetism in strongly correlated electron systems with Ising-type ferromagnetic (FM) behaviour is intensively studied because it produces a variety of unconventional effects. In some itinerant ferromagnets, such as UGe 2 1, 2 or ZrZn 2 , 3 one can drive the Curie temperature T C to 0 K by tuning an external control parameter like pressure, and the ground state is found to be paramagnetic (PM) above the quantum critical point (QCP). In theory, it has been suggested -and in some cases experimentally shown -that the second order ferromagnetic transition changes to first order at a tricritical point. 4 By applying a magnetic field above the critical point in the paramagnetic phase, such systems eventually recover their ferromagnetic state by undergoing a first-order metamagnetic transition at B m , drawing a wing-shape first order transition plane in the temperature (T ) -pressure (P ) -field (B) phase diagram. The first order transition terminates at high pressure and high field at T = 0 at the so-called quantum critical end point (QCEP). In this critical region, only few experiments were carried out because of the severe experimental conditions of low temperature, high pressure, and high field. [1][2][3]5 Due to the recent focus on quantum criticality, the metamagnetism in itinerant ferromagnets has been recently revisited theoretically (see e.g. Ref. 6,7). The main debate is whether a Lifshitz-like transition is associated with the occurence of metamagnetism.A good candidate to investigate itinerant metamagnetism is the heavy fermion compound UCoAl, with ZrNiAl-type hexagonal structure, space group P62m. At ambient pressure, its ground state is paramagnetic, with strong uniaxial magnetic anisotropy. By applying mag-

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A change of the Fermi surface in UGe₂across the critical pressure

Cited by 63 publications

References 19 publications

Metallic ferromagnetism in the Kondo lattice

Metallic ferromagnetism in the Kondo lattice

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

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A change of the Fermi surface in UGe2across the critical pressure

Cited by 63 publications

References 19 publications

Metallic ferromagnetism in the Kondo lattice

Metallic ferromagnetism in the Kondo lattice

Recent Advances in the Magnetism and Superconductivity of Heavy Fermion Systems

Ferromagnetic Quantum Criticality Studied by Hall Effect Measurements in UCoAl

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A change of the Fermi surface in UGe₂across the critical pressure