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1.
Understanding the nature of field-tuned metamagnetic quantum criticality in the ruthenate Sr3Ru2O7 has presented a significant challenge within condensed matter physics. It is known from experiments that the entropy within the ordered phase forms a peak, and is unexpectedly higher than that outside, while the magnetoresistivity experiences steep jumps near the ordered phase. We find a challenging connection between Sr3Ru2O7 and heavy-fermion metals expressing universal physics that transcends microscopic details. Our construction of the T–B phase diagram of Sr3Ru2O7 permits us to explain main features of the experimental one, and unambiguously implies an interpretation of its extraordinary low-temperature thermodynamic in terms of fermion condensation quantum phase transition leading to the formation of a flat band at the restricted range of magnetic fields B. We show that it is the flat band that generates both the entropy peak and the resistivity jumps at the QCPs. 相似文献
2.
In this paper the low-temperature properties of two isostructural canonical heavy-fermion compounds are contrasted with regards to the interplay between antiferromagnetic (AF) quantum criticality and superconductivity. For CeCu2Si2, fully-gapped d-wave superconductivity forms in the vicinity of an itinerant three-dimensional heavy-fermion spin-density-wave (SDW) quantum critical point (QCP). Inelastic neutron scattering results highlight that both quantum critical SDW fluctuations as well as Mott-type fluctuations of local magnetic moments contribute to the formation of Cooper pairs in CeCu2Si2. In YbRh2Si2, superconductivity appears to be suppressed at T???10?mK by AF order (TN?=?70?mK). Ultra-low temperature measurements reveal a hybrid order between nuclear and 4f-electronic spins, which is dominated by the Yb-derived nuclear spins, to develop at TA slightly above 2?mK. The hybrid order turns out to strongly compete with the primary 4f-electronic order and to push the material towards its QCP. Apparently, this paves the way for heavy-fermion superconductivity to form at Tc?=?2?mK. Like the pressure – induced QCP in CeRhIn5, the magnetic field – induced one in YbRh2Si2 is of the local Kondo-destroying variety which corresponds to a Mott-type transition at zero temperature. Therefore, these materials form the link between the large family of about fifty low-T unconventional heavy – fermion superconductors and other families of unconventional superconductors with higher Tcs, notably the doped Mott insulators of the cuprates, organic charge-transfer salts and some of the Fe-based superconductors. Our study suggests that heavy-fermion superconductivity near an AF QCP is a robust phenomenon. 相似文献
3.
The transport properties of the semimetallic quasi-one-dimensional S=1/2 antiferromagnet Yb4As3 have been studied by performing low-temperature (T≥0.02 K) and high magneticfield (B≤60 T) measurements of the electrical resistivity ρ(T, B). For T ≿ 2 K a ‘heavy-fermion’-like behavior Δρ(T)=AT
2 with huge and nearly field-independent coefficient A ≈ 3 μΩ cm/K2 is observed, whereas at lower temperatures ρ(T) deviates from this behavior and slightly increases to the lowest T. In B>0 and T ≾ 6 K the resistivity shows an anomalous magnetic-history dependence together with an unusual relaxation behavior. In the
isothermal resistivity Shubnikov-de Haas (SdH) oscillations, arising from a low-density system of mobile As-4p holes, with a frequency of 25 T have been recorded. From the T- and B-dependence of the SdH oscillations an effective carrier mass of (0.275±0.005)m
0 and a charge-carrier mean-free path of 215 ? are determined. Furthermore, in B≥15 T, the system is near the quantum limit and spin-splitting effects are observed. 相似文献
4.
A. V. Golubkov L. S. Parfen’eva I. A. Smirnov H. Misiorek J. Mucha A. Jezowski 《Physics of the Solid State》2006,48(4):625-630
The thermal conductivity κ and electrical resistivity ρ of a cast polycrystalline sample of YbIn0.2Ag0.8Cu4, which belongs to the class of moderate heavy-fermion compounds, are measured in the temperature range 5–300 K. It is shown that the phonon thermal conductivity of the sample follows an amorphous-like pattern throughout the temperature range covered, which should be assigned to the presence of Yb ions with a homogeneous mixed valence in this compound. The temperature dependence ρ(T) is divided into three portions: a high-temperature portion characteristic of conventional metals, a medium-temperature portion typical of Kondo compounds, and a low-temperature portion corresponding to a coherent Kondo lattice (the heavy-fermion regime). The Kondo temperature is estimated. 相似文献
5.
L.J. LiW.J. Lu X.D. ZhuX.B. Zhu Z.R. YangW.H. Song Y.P. Sun 《Journal of magnetism and magnetic materials》2011,323(21):2536-2541
The low-Mn-intercalated compounds 2H-MnxTaS2 (x≤0.1) single crystals were successfully grown via the iodine chemical vapor transport technique; the electrical and magnetic properties have been investigated systematically. No signs of charge density wave and superconductivity transitions appear down to 2 K even when x=0.02, while a small resistivity upturn has been observed in the low-temperature region for MnxTaS2 samples. A substantial magnetocrystalline anisotropy is observed and the Mn magnetic moments lie mainly parallel to the ab-plane. The glass behavior was observed in the low-temperature region firstly from the ac susceptibility measurement, the freezing of the glass may contribute to the upturn of the resistivity. 相似文献
6.
Work function changes ΔΦ caused by H2 interaction with thin terbium and europium films deposited on glass under UHV conditions were correlated with hydrogen uptake and electrical resistance R, measured in situ. For both metals, the course of ΔΦ(H/Me) at room temperature confirms the change in charge-transfer direction on the surface during hydride formation. As a result, the hydrogen adsorbate's nature is changed from positively polarized (precursor state) to negatively polarized adspecies. The hydrogen behavior is significantly different at low temperature due to the formation of the surface ordered low-temperature phase (α′) with positively polarized hydrogen adspecies. This phase, strongly inhibiting penetration of hydrogen into the bulk, is stable up to 100 K for terbium and 160 K for europium. Increasing temperature above these values resulted in additional large absorption of hydrogen. Moreover, differences in the course of R(H/Me) are clearly noticeable between the investigated metals. The resistance of thin TbHx (x ∼ 3) films in our experiments did not exceed 1 kΩ, however transition of thin metallic europium film into EuHy (y ∼ 2) increased the resistance up to 10 MΩ. This dissimilarity in electrical behavior can be explained by the coexistence of two factors which are different for the two metals in question: the phase relation of hydrides and the response of thin film to stress generated during hydride formation. 相似文献
7.
V. R. Shaginyan K. G. Popov V. A. Khodel 《Journal of Experimental and Theoretical Physics》2013,116(5):848-853
Strongly correlated Fermi systems are among the most intriguing and fundamental systems in physics. We show that the herbertsmithite ZnCu3(OH)6Cl2 can be regarded as a new type of strongly correlated electrical insulator that possesses properties of heavy-fermion metals with one exception: it resists the flow of electric charge. We demonstrate that herbertsmithite’s low-temperature properties are defined by a strongly correlated quantum spin liquid made with hypothetic particles such as fermionic spinons that carry spin 1/2 and no charge. Our calculations of its thermodynamic and relaxation properties are in good agreement with recent experimental facts and allow us to reveal their scaling behavior, which strongly resembles that observed in heavy-fermion metals. Analysis of the dynamic magnetic susceptibility of strongly correlated Fermi systems suggests that there exist at least two types of its scaling. 相似文献
8.
We report on the formation of a novel ternary compound Ce2PdIn8 that is isostructural with the heavy-fermion superconductors Ce2CoIn8 and Ce2RhIn8. Its magnetic, electrical transport and thermodynamic properties were studied on polycrystalline samples in wide ranges of temperature and magnetic field strength. The results revealed Ce2PdIn8 to be a paramagnetic Kondo lattice with a coherence temperature of about 12 K. The C/T ratio of the specific heat reaches at 350 mK a strongly enhanced magnitude of about per Ce-atom, thus clearly indicating a heavy-fermion nature of this material. Moreover, a logarithmic divergence of C/T vs. T, observed below 3 K, which is accompanied by a linear temperature dependence of the electrical resistivity below 6 K, hint at a non-Fermi liquid character of the electronic ground state in the new compound reported. 相似文献
9.
Küchler R Gegenwart P Custers J Stockert O Caroca-Canales N Geibel C Sereni JG Steglich F 《Physical review letters》2006,96(25):256403
We report a comprehensive study of CeIn3-xSnx (0.55相似文献
10.
Basing on the density functional theory of fermion condensation, we analyze the non-Fermi liquid behavior of strongly correlated Fermi-systems such as heavy-fermion metals. When deriving equations for the effective mass of quasiparticles, we consider solids with a lattice and homogeneous systems. We show that the low-temperature thermodynamic and transport properties are formed by quasiparticles, while the dependence of the effective mass on temperature, number density, magnetic fields, etc., gives rise to the non-Fermi liquid behavior. Our theoretical study of the heat capacity, magnetization, energy scales, the longitudinal magnetoresistance and magnetic entropy are in good agreement with the remarkable recent facts collected on the heavy-fermion metal YbRh2Si2. 相似文献
11.
A. Budziak M. ?urekJ. ?ukrowski M. Ba?andaA. Pacyna M. Czapla 《Journal of magnetism and magnetic materials》2012,324(5):735-741
The HoMn2 compound crystallizes in the cubic C15 or hexagonal C14 Laves phases depending on preparation. The effect of hydrogen absorption on structural and magnetic properties of HoMn2Hx hydrides for the C14 phase has been investigated by XRD and AC/DC magnetometry in the temperature ranges of 75-380 K and 4-390 K, respectively. In addition to general features revealed by RMn2Hx compounds (R=rare earth or Yttrium), unusual behavior of these hydrides was found. In particular, a transformation from the hexagonal to the monoclinic structure was detected, the same as that observed for cubic HoMn2Hx compounds. The structural transformations are correlated to the magnetic behavior. The presented results are compared mainly with the properties of the cubic HoMn2Hx hydrides as well as with those of other RMn2Hx hydrides. Tentative magnetic and structural phase diagrams are proposed. 相似文献
12.
N. E. Sluchanko A. V. Bogach V. V. Glushkov S. V. Demishev M. I. Ignatov N. A. Samarin G. S. Burkhanov O. D. Chistyakov 《Journal of Experimental and Theoretical Physics》2004,98(4):793-810
The Hall coefficient R H , resistivity ρ, and Seebeck coefficient S of the CeAl2 compound with fast electron density fluctuations were studied in a wide temperature range (from 1.8 to 300 K). Detailed measurements of the angular dependences R H (? T, H≤70 kOe) were performed to determine contributions to the anomalous Hall effect and study the behavior of the anomalous magnetic R H am and main R H a components of the Hall signal of this compound with strong electron correlation. The special features of the behavior of the anomalous magnetic component R H am were used to analyze the complex magnetic phase diagram H-T determined by magnetic ordering in the presence of strong spin fluctuations. An analysis of changes in the main contribution R H a (H, T) to the Hall effect made it possible to determine the complex activation behavior of this anomalous component in the CeAl2 intermetallic compound. The results led us to conclude that taking into account spin-polaron effects was necessary and that the Kondo lattice and skew-scattering models were of very limited applicability as methods for describing the low-temperature transport of charge carriers in cerium-based intermetallic compounds. The effective masses and localization radii of manybody states in the CeAl2 matrix were estimated to be (55–90)m0 and 6–10 Å, respectively. The behaviors of the parameters R H , S, and ρ were jointly analyzed. The results allowed us to consistently describe the transport coefficients of CeAl2. 相似文献
13.
Quantum oscillations of the resistivity ??22 and Hall coefficient R 12.3 in the semiconductor alloy n-Bi0.93Sb0.07 have been studied at H ?? C 3 and j ?? C 1 in magnetic fields to 14 T and at temperatures of 1.5, 4.5, 10, and 20 K. At temperatures of 1.5 and 4.5 K, beats of quantum oscillations of ??22 and R 12.3 due to a small deviation of the magnetic field H from the crystallographic C 3 axis have been observed. To determine the oscillation period ?? i , cyclotron mass m ci , cyclotron frequency ?? ci , and extreme section S extri, experimentally measured quantum oscillation beats have been compared with the model beats of oscillations of three harmonic functions, two of which have close frequencies. The deviation of the parameters ?? i , m ci , and S extri from the same parameters when the magnetic field H exactly coincides with the trigonal C 3 axis has made it possible to estimate the magnetic field H deflection angle from the trigonal C 3 axis, which is ??1°. 相似文献
14.
The question of whether the temperature dependences of the magnetic susceptibility and the electrical resistivity of UCu5−xNix near, and away from, the QCP where TN is suppressed to T = 0 are due to intrinsic fluctuations or are dominated by disorder effects is addressed. The interesting ρ ∝ log T behavior below 2 K present for 0.75 ? x ? 1.1 is analyzed and discussed. 相似文献
15.
《Physics letters. A》1987,125(5):267-270
Thermodynamic and electrodynamic properties of heavy-fermion superconductors are studied in a two-band model with interband (“hybrid”) singlet pairing. The general form of electron-electron interaction is analyzed and it is shown in particular that antiferromagnetic spin fluctuations increase the tendency to such a pairing. The expression for the free energy functional is obtained and the behaviour of the correlation length Hc2 and the London penetration depth at T = 0 and T→Tc is investigated. The model discussed gives reasonable qualitative agreement with the properties of heavy-fermion superconductors. 相似文献
16.
The temperature behavior of I-U curves and the field and temperature dependences of the electrical resistivity and dielectric permittivity of crystals of the LiCu2O2 phase have been studied. It was established that the crystals belong to p-type semiconductors and that their static resistivity in the range 80–260 K follows the Mott law ρ=Aexp(T0/T)1/4 describing variable-range hopping over localized states. At comparatively low electric fields, the crystals exhibit threshold switching and characteristic S-shaped I-U curves containing a region of negative differential resistivity. In the critical voltage region, jumps in the conductivity and dielectric permittivity are observed. Possible mechanisms of the disorder and electrical instability in these crystals are discussed. 相似文献
17.
E.D. Mun S.L. Bud’ko G.J. Miller 《Journal of magnetism and magnetic materials》2010,322(21):3527-3543
We have studied RNiGe3 (R=Y, Ce-Nd, Sm, Gd-Lu) single crystals by measuring crystal structure and stoichiometry, magnetic susceptibility, magnetization, electrical resistivity, magnetoresistance, and specific heat. Clear anisotropies as well as antiferromagnetic ordering in the RNiGe3 series (R=Ce-Nd, Sm, Gd-Tm) have been observed above 1.8 K from the magnetic susceptibility. A metamagnetic transition in this family (except for R=Sm) was detected at 2 K for applied magnetic fields below 70 kOe. The electrical resistivity of this series follows metallic behavior in the high temperature region. Below the antiferromagnetic ordering temperature a significant anisotropy is exhibited in the resistivity and magnetoresistance for different current directions. The anisotropic magnetic, transport, and thermal properties of RNiGe3 compounds are discussed in terms of Ni site occupancy as well as a combination of the effect of formation of a magnetic superzone gap and the crystalline electric field. 相似文献
18.
Measurements of the electrical resistivity of 1T-TaS2 to 0.03 K show that the increase in resistivity below ~ 50 K is extrinsic.Below 2 K the resistivity is described by ? = ?0 exp . Because of this fractional power law behavior, we conclude that the increase is due to Anderson localization by random impurity and/or defect potentials. Other difficulties in understanding the properties of 1T-TaS2 are also pointed out. 相似文献
19.
20.
We propose a theory describing low-temperature properties of magnets with integer spin and large single-ion easy-plane anisotropy
D in magnetic field H directed parallel to the hard axis. Considering the exchange interaction between spins as a perturbation and using the bosonic
spin representation proposed in our recent paper [1] we find thermal corrections to the elementary excitation spectrum, magnetization
and specific heat in the vicinity of the quantum critical point (QCP) H = H
c1(0) ∼ D in the first nonvanishing orders of the perturbation theory. An expression is found for the boundary of the paramagnetic
phase H
c1(T) in the H-T plane. The effective interaction between bosons is derived near the QCP. The proposed theory describes well experimental
data obtained in NiCl2-4SC(NH2)2 (DTN). 相似文献