Abstract
Superconductivity appears in the cuprates when a spin order is destroyed, while the role of charge is less known. Recently, charge density wave (CDW) was found below the superconducting dome ...in YBa
2
Cu
3
O
y
when a high magnetic field is applied perpendicular to the CuO
2
plane, which was suggested to arise from incipient CDW in the vortex cores that becomes overlapped. Here by
63
Cu-nuclear magnetic resonance, we report the discovery of CDW induced by an in-plane field, setting in above the dome in single-layered Bi
2
Sr
2−
x
La
x
CuO
6
. The onset temperature
T
CDW
takes over the antiferromagnetic order temperature
T
N
beyond a critical doping level at which superconductivity starts to emerge, and scales with the pseudogap temperature
T
*. These results provide important insights into the relationship between spin order, CDW and the pseudogap, and their connections to high-temperature superconductivity.
Superconductivity appears in the cuprates when a spin order is destroyed, while the role of charge is less known. Recently, charge density wave (CDW) was found below the superconducting dome in YBa
2
...Cu
3
O
y
when a high magnetic field is applied perpendicular to the CuO
2
plane, which was suggested to arise from incipient CDW in the vortex cores that becomes overlapped. Here by
63
Cu-nuclear magnetic resonance, we report the discovery of CDW induced by an in-plane field, setting in above the dome in single-layered Bi
2
Sr
2−
x
La
x
CuO
6
. The onset temperature
T
CDW
takes over the antiferromagnetic order temperature
T
N
beyond a critical doping level at which superconductivity starts to emerge, and scales with the pseudogap temperature
T
*. These results provide important insights into the relationship between spin order, CDW and the pseudogap, and their connections to high-temperature superconductivity.
Whilst superconductivity usually appears when magnetic order is suppressed, the role of charge is less known. Here, Kawasaki et al. report a charge density wave (CDW) above the superconducting transition induced by an in-plane magnetic field in Bi
2
Sr
2-
x
La
x
CuO
6
, with the CDW onset temperature scaling with the pseudogap temperature.
Charge order in cuprate superconductors appears to be a universal characteristic, often associated with pseudogap behavior in the normal state. The central question is whether such charge ordering or ...the pseudogap are required for the existence of high temperature superconductivity and embody its mechanism. An important but phenomenological approach to this question is to examine whether these phenomena extend over various members of the cuprate family. Recent nuclear magnetic resonance (NMR) measurements on oxygen chain-ordered single crystals of YBa2Cu3O6+y (Y123) have demonstrated temperature and magnetic field induced charge ordering that was confirmed in x-ray experiments. In the present work on high-quality single crystals of the tetragonal compound, HgBa2CuO4+δ, we use 17O NMR to investigate the interplay between charge and spin order deduced from the full quadrupolar-split NMR spectrum over a wide range of temperature and magnetic field. We have found evidence for a coherent modulation of charge and spin order in this compound. However, neither temperature nor magnetic field induced ordering was observed and we infer that this aspect of high temperature superconductivity is not universal.
The simple structure of HgBa(2)CuO(4+δ) (Hg1201) is ideal among cuprates for study of the pseudogap phase as a broken symmetry state. We have performed (17)O nuclear magnetic resonance on an ...underdoped Hg1201 crystal with a transition temperature of 74 K to look for circulating loop currents proposed theoretically and inferred from neutron scattering. The narrow spectra preclude static local fields in the pseudogap phase at the apical site, suggesting that the moments observed with neutrons are fluctuating. The nuclear magnetic resonance frequency shifts are consistent with a dipolar field from the Cu(2+) site.
We apply strong magnetic fields of H=28.5 to 43 T to suppress superconductivity (SC) in the cuprates Bi2Sr2-xLaxCuO6+delta (x=0.65, 0.40, 0.25, 0.15, and 0), and investigate the low temperature (T) ...normal state by 63Cu nuclear spin-lattice relaxation rate (1/T1) measurements. We find that the pseudogap (PG) phase persists deep inside the overdoped region but terminates at x approximately 0.05, which corresponds to the hole doping concentration of approximately 0.21. Beyond this critical point, the normal state is a Fermi liquid that persists as the ground state when superconductivity is removed by the magnetic field. A comparison of the superconducting state with the H-induced normal state in the x=0.40 (Tc=32 K) sample indicates that there remains substantial part of the Fermi surface even in the fully developed PG state, which suggests that the PG and SC are coexisting matters.
For certain compositions Ni-Mn-Sn and related magnetic shape-memory alloys undergo a martensitic transition at temperatures in the range 300-400 K, with the emergence of novel magnetic properties ...below the transition. While Ni sub(50)Mn sub(50) is an antiferromagnet, substitution of Sn on some fraction of the Mn sites in Ni sub(50)Mn sub(50-x)Sn sub(x) leads to competing ferromagnetic (F) and antiferromagnetic (AF) phases at low temperatures. Details of this magnetic phase coexistence are, however, significantly lacking, particularly with respect to the AF phase. The present investigations use zero applied magnetic field super(55)Mn NMR as a local probe of the magnetic properties of the alloy Ni sub(50)Mn sub(50-x)Sn sub(x) with x = 10. Rich multipeak spectra are observed, and the various components are definitively assigned to nanoscale F or AF regions. Measurements of the static nuclear hyperfine field distributions as a function of temperature, and in small applied fields, together with nuclear relaxation rates provide detailed information on the size distributions, relative concentrations, and physical natures of these F and AF regions. The results show that the nanoscale magnetic features of the x = 10 system are substantially more complex than previous studies have suggested. We argue that the general approach used in these experiments is applicable to other such complex metal alloys, and could yield many additional insights.
Electronic inhomogeneity in a Kondo lattice Bauer, E. D.; Yang, Yi-feng; Capan, C. ...
Proceedings of the National Academy of Sciences - PNAS,
04/2011, Letnik:
108, Številka:
17
Journal Article
Recenzirano
Odprti dostop
Inhomogeneous electronic states resulting from entangled spin, charge, and lattice degrees of freedom are hallmarks of strongly correlated electron materials; such behavior has been observed in many ...classes of d-electron materials, including the high-Tc copperoxide superconductors, manganites, and most recently the ironpnictide superconductors. The complexity generated by competing phases in these materials constitutes a considerable theoretical challenge—one that still defies a complete description. Here, we report a manifestation of electronic inhomogeneity in a strongly correlated f-electron system, using CeColn₅ as an example. A thermodynamic analysis of its superconductivity, combined with nuclear quadrupole resonance measurements, shows that nonmagnetic impurities (Y, La, Yb, Th, Hg, and Sn) locally suppress unconventional superconductivity, generating an inhomogeneous electronic "Swiss cheese" due to disrupted periodicity of the Kondo lattice. Our analysis may be generalized to include related systems, suggesting that electronic inhomogeneity should be considered broadly in Kondo lattice materials.
Charge order in cuprate superconductors appears to be a universal characteristic, often associated with pseudogap behavior in the normal state. The central question is whether such charge ordering or ...the pseudogap are required for the existence of high temperature superconductivity and embody its mechanism. An important but phenomenological approach to this question is to examine whether these phenomena extend over various members of the cuprate family. Recent nuclear magnetic resonance (NMR) measurements on oxygen chain-ordered single crystals of YBa2Cu3O6+y (Y123) have demonstrated temperature and magnetic field induced charge ordering that was confirmed in x-ray experiments. In the present work on high-quality single crystals of the tetragonal compound, HgBa2CuO4+δ, we use 17O NMR to investigate the interplay between charge and spin order deduced from the full quadrupolar-split NMR spectrum over a wide range of temperature and magnetic field. We have found evidence for a coherent modulation of charge and spin order in this compound. Furthermore, neither temperature nor magnetic field induced ordering was observed and we infer that this aspect of high temperature superconductivity is not universal.
Single crystals of the new multiferroic Ba3NbFe3Si2O14 have been synthesized and characterized via X-ray diffraction, magnetic susceptibility, NMR, and electric polarization measurements. The ...underlying topology of the Fe 3+ spins is composed of isolated triangular units stacked in 2D layers along the c-direction of the trigonal lattice. Magnetic susceptibility experiments verify the spin state of the iron moments (S = 5/2), and large antiferromagnetic interactions with θ = −190 K. A cusp in the susceptibility and lambda-like feature in the specific heat indicate a magnetic phase transition at T N = 26 K, resulting in a frustration index of f = 7. A significant amount of spin entropy is released at higher temperatures, suggestive of short-ranged magnetic correlations developing at 50 K (as evidenced by features in the specific heat and thermal conductivity). The development of a spontaneous electric polarization below 26 K verifies that Ba3NbFe3Si2O14 is a multiferroic.
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