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46 46

Specific heat measurements of the gap structure of the organic superconductors kappa-(ET)_2Cu[N(CN)_2]Br and kappa-(ET)_2Cu(NCS)_2

Sep 19, 2013 09/13

by O. J. Taylor; A. Carrington; J. A. Schlueter

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We present high resolution heat capacity measurements for the organic superconductors kappa-(ET)_2Cu[N(CN)_2]Br and kappa-(ET)_2Cu(NCS)_2 in fields up to 14 T. We use the high field data to determine the normal state specific heat and hence extract the behavior of the electronic specific heat C_{el} in the superconducting state in zero and finite fields. We find that in both materials for T/T_c
Source: http://arxiv.org/abs/cond-mat/0703673v1

Arxiv.org

56 56

Superconductor-Insulator Phase Separation Induced by Rapid Cooling in kappa-(ET)_2Cu[N(CN)_2]Br

Sep 23, 2013 09/13

by O. J. Taylor; A. Carrington; J. A. Schlueter

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We present measurements of the low temperature specific heat of single crystals of kappa-(ET)_2Cu[N(CN)_2]Br as a function of the cooling rate through the glasslike structure transition at $\sim$ 80K. We find that rapid cooling produces a small ( < 4%) decrease in the superconducting transition temperature accompanied by a substantial (up to 50%) decrease in the normal-state electronic specific heat. A natural explanation of our data is that there is a macroscopic phase separation between...
Source: http://arxiv.org/abs/0801.2502v1

Arxiv.org

55 55

Location of gap nodes in the organic superconductors $κ$-(ET)$_2$Cu(NCS)$_2$ and $κ$-(ET)$_2$Cu[N(CN)$_2$]Br determined by magnetocalorimetry

Sep 21, 2013 09/13

by L. Malone; O. J. Taylor; J. A. Schlueter; A. Carrington

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We report specific heat measurements of the organic superconductors $\kappa$-(ET)$_2$Cu(NCS)$_2$ and $\kappa$-(ET)$_2$Cu[N(CN)$_2$]Br. When the magnetic field is rotated in the highly conducting planes at low temperature ($T\simeq 0.4$ K), we observe clear oscillations of specific heat which have a strong fourfold component. The observed strong field and temperature dependence of this fourfold component identifies it as originating from nodes in the superconducting energy gap which point along...
Source: http://arxiv.org/abs/0905.2342v2

Arxiv.org

73 73

Superconductivity and fluctuating magnetism in quasi two-dimensional kappa-(BEDT-TTF)2Cu[N(CN)2]Br probed with implanted muons

Jul 20, 2013 07/13

by T. Lancaster; S. J. Blundell; F. L. Pratt; J. A. Schlueter

eye 73

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A muon-spin relaxation (muSR) investigation is presented for the molecular superconductor kappa-(BEDT-TTF)2Cu[N(CN)2Br]. Evidence is found for low-temperature phase-separation, with only a fraction of the sample showing a superconducting signal, even for slow cooling. Rapid cooling reduces the superconducting fraction still further. For the superconducting phase, the in-plane penetration depth is measured to be lambda_{parallel} = 0.47(1) mu m and evidence is seen for a vortex decoupling...
Source: http://arxiv.org/abs/1007.0148v1

Arxiv.org

50 50

Comparison of the Fermi-surface topologies of kappa-(BEDT-TTF)_2 Cu(NCS)_2 and its deuterated analogue

Sep 19, 2013 09/13

by R. S. Edwards; A. Narduzzo; J. Singleton; A. Ardavan; J. A. Schlueter

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We have measured details of the quasi one-dimensional Fermi-surface sections in the organic superconductor kappa-(BEDT-TTF)_2 Cu(NCS)_2 and its deuterated analogue using angle-dependent millimetre-wave techniques. There are significant differences in the corrugations of the Fermi surfaces in the deuterated and undeuterated salts. We suggest that this is important in understanding the inverse isotope effect, where the superconducting transition temperature rises on deuteration. The data support...
Source: http://arxiv.org/abs/cond-mat/0208086v1

Arxiv.org

6 6.0

Microscopic study of the Fulde-Ferrell-Larkin-Ovchinnikov state in an all-organic superconductor

Jun 28, 2018 06/18

by G. Koutroulakis; H. Kühne; J. A. Schlueter; J. Wosnitza; S. E. Brown

eye 6

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Quasi-two dimensional superconductors with sufficiently weak interlayer coupling allow magnetic flux to penetrate in the form of Josephson vortices for in-plane applied magnetic fields. A consequence is the dominance of the Zeeman interaction over orbital effects. In the clean limit, the normal state is favored over superconductivity for fields greater than the paramagnetic limiting field, unless an intermediate, inhomogeneous state is stabilized. Presented here are nuclear magnetic resonance...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1511.03758

Arxiv.org

3 3.0

$ESR studies on the spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: anomalous response below $T=8$ K$

ESR studies on the spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: anomalous response below $T=8$ K

Jun 30, 2018 06/18

by K. G. Padmalekha; M. Blankenhorn; T. Ivek; L. Bogani; J. A. Schlueter; M. Dressel

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The organic conductor $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$ seems to form a quantum spin liquid, although at low temperatures unusual properties are seen in the charge, spin and lattice degrees of freedom. Here we report results of X-band ESR studies of $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$ single crystals as a function of temperature and angle. We find indications of two anisotropic relaxation mechanisms at low temperatures and compare them to the spin-liquid behavior observed in other...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1409.2033

Arxiv.org

61 61

Paramagnetic limiting of the upper critical field of the layered organic superconductor $κ-(BEDT-TTF)_2Cu(SCN)_2$

Sep 23, 2013 09/13

by F. Zuo; J. S. Brooks; Ross H. McKenzie; J. A. Schlueter; Jack M. Williams

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We report detailed measurements of the interlayer magnetoresistance of the layered organic superconductor $\kappa -(BEDT-TTF)_2Cu(SCN)_2$ for temperatures down to 0.5 K and fields up to 30 tesla. The upper critical field is determined from the resistive transition for a wide range of temperatures and field directions. For magnetic fields parallel to the layers, the upper critical field increases approximately linearly with decreasing temperature. The upper critical field at low temperatures is...
Source: http://arxiv.org/abs/cond-mat/9904186v1

Arxiv.org

14 14

$Origin of the glass-like dynamics in molecular metals $\pmb{\kappa}$-(BEDT-TTF)$_{\textbf{2}}$X: implications from fluctuation spectroscopy and $\pmb{\textit{ab initio}}$ calculations$

Origin of the glass-like dynamics in molecular metals $\pmb{\kappa}$-(BEDT-TTF)$_{\textbf{2}}$X: implications from fluctuation spectroscopy and $\pmb{\textit{ab initio}}$ calculations

Jun 28, 2018 06/18

by J. Müller; B. Hartmann; R. Rommel; J. Brandenburg; S. M. Winter; J. A. Schlueter

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We have studied the low-frequency dynamics of the charge carriers in different organic charge-transfer salts $\kappa$-(BEDT-TTF)$_2$X with polymeric anions X by using resistance noise spectroscopy. Our aim is to investigate the structural, glass-like transition caused by the conformational degrees of freedom of the BEDT-TTF molecules' terminal ethylene groups. Although of fundamental importance for studies of the electronic ground-state properties, the phenomenology of the glassy dynamics is...
Topics: Strongly Correlated Electrons, Condensed Matter, Materials Science
Source: http://arxiv.org/abs/1506.05191

Arxiv.org

75 75

$Evidence for structural and electronic instabilities at intermediate temperatures in $κ$-(BEDT-TTF)$_{2}$X for X=Cu[N(CN)$_{2}$]Cl, Cu[N(CN)$_{2}$]Br and Cu(NCS)$_{2}$: Implications for the phase diagram of these quasi-2D organic superconductors$

Evidence for structural and electronic instabilities at intermediate temperatures in $κ$-(BEDT-TTF)$_{2}$X for X=Cu[N(CN)$_{2}$]Cl, Cu[N(CN)$_{2}$]Br and Cu(NCS)$_{2}$: Implications for the phase diagram of these quasi-2D organic superconductors

Jul 20, 2013 07/13

by J. Müller; M. Lang; F. Steglich; J. A. Schlueter; A. M. Kini; T. Sasaki

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We present high-resolution measurements of the coefficient of thermal expansion $\alpha (T)=\partial \ln l(T)/\partial T$ of the quasi-twodimensional (quasi-2D) salts $\kappa$-(BEDT-TTF)$_2$X with X = Cu(NCS)$_2$, Cu[N(CN)$_2$]Br and Cu[N(CN)$_2$]Cl. At intermediate temperatures (B), distinct anomalies reminiscent of second-order phase transitions have been found at $T^\ast = 38$ K and 45 K for the superconducting X = Cu(NCS)$_2$ and Cu[N(CN)$_2$]Br salts, respectively. Most interestingly, we...
Source: http://arxiv.org/abs/cond-mat/0107480v1

Arxiv.org

49 49

Comparative magnetotransport and Tc measurements on kappa-(BEDT-TTF)2Cu(SCN)2 under pressure

Sep 20, 2013 09/13

by A. -K. Klehe; T. Biggs; C. A. Kuntscher; A. M. Kini; J. A. Schlueter

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We compare magnetotransport measurements under pressure on the organic superconductor $\kappa$-(BEDT-TTF)$_{2}$Cu(SCN)$_{2}$ with different pressure-media and discover that the results are pressure media dependent. This pressure-medium dependence is thought to originate from the difference in thermal contraction between the very soft and highly anisotropic sample and the isotropically contracting, but solid pressure medium, thus resulting in non-hydrostatic pressure on the sample. However,...
Source: http://arxiv.org/abs/cond-mat/0405445v2

Arxiv.org

3 3.0

$Low-Energy Excitations in the Quantum Spin-Liquid $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$$

Low-Energy Excitations in the Quantum Spin-Liquid $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$

Jun 30, 2018 06/18

by A. Pustogow; E. Zhukova; B. Gorshunov; M. Pinterić; S. Tomić; J. A. Schlueter; M. Dressel

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The electrodynamic response of the organic spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ has been measured in an extremely wide energy range ($10^{-13}$ to 2 eV) as a function of temperature (5 to 300 K). Below the Mott gap, excitations from the un-gapped spinon continuum cause a considerable contribution to the infrared conductivity, as suggested by the U(1) gauge theory. At THz frequencies we can identify a power-law behavior $\sigma(\omega) \propto \omega^{\beta}$ with two...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1412.4581

Arxiv.org

3 3.0

$Charge fluctuations and superconductivity in organic conductors: the case of $\beta"$-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$$

Charge fluctuations and superconductivity in organic conductors: the case of $\beta"$-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$

Jun 29, 2018 06/18

by G. Koutroulakis; H. Kühne; H. H. Wang; J. A. Schlueter; J. Wosnitza; S. E. Brown

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A $^{13}$C NMR study of the normal and superconducting states of the all-organic charge-transfer salt $\beta"$-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$ is presented. We find that the normal state is a charge-ordered metal configured as vertical stripes, produced by a combination of 1/4-filling, correlations, and a polar counterion sublattice. The NMR properties associated with the superconducting state are consistent with gap nodes and singlet pairing, and therefore similar to other organic...
Topics: Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1601.06107

Arxiv.org

49 49

Bandwidth tuning triggers interplay of charge order and superconductivity in two-dimensional organic materials

Sep 22, 2013 09/13

by S. Kaiser; M. Dressel; Y. Sun; A. Greco; J. A. Schlueter; G. L. Gard; N. Drichko

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We observe charge-order fluctuations in the quasi-two-dimensional organic superconductor $\beta^{\prime\prime}$-(BEDT-TTF)2 SF5 CH2 CF2 SO3 both by means of vibrational spectroscopy, locally probing the fluctuating charge order, and investigating the in-plane dynamical response by infrared reflectance spectroscopy. The decrease of effective electronic interaction in an isostructural metal suppresses both charge-order fluctuations and superconductivity, pointing on their interplay. We compare...
Source: http://arxiv.org/abs/0812.3732v2

Arxiv.org

51 51

$Upper critical field study in the organic superconductor $β''$-(ET)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$ : Possibility of Fulde-Ferrell-Larkin-Ovchinnikov state$

Upper critical field study in the organic superconductor $β''$-(ET)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$ : Possibility of Fulde-Ferrell-Larkin-Ovchinnikov state

Sep 22, 2013 09/13

by K. Cho; B. E. Smith; W. A. Coniglio; L. E. Winter; C. C. Agosta; J. A. Schlueter

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We report upper critical field measurements in the metal-free-all-organic superconductor $\beta''$-(ET)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$ obtained from measuring the in-plane penetration depth using the tunnel diode oscillator technique. For magnetic field applied parallel to the conducting planes the low temperature upper critical fields are found to exceed the Pauli limiting field calculated by using a semi-empirical method. Furthermore, we found a signature that could be the phase...
Source: http://arxiv.org/abs/0811.3647v2

Arxiv.org

43 43

Resistivity studies under hydrostatic pressure on a low-resistance variant of the quasi-2D organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br: quest for intrinsic scattering contributions

Sep 21, 2013 09/13

by C. Strack; C. Akinci; B. Wolf; M. Lang; J. A. Schlueter; J. Wosnitza; D. Schweitzer; J. Mueller

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Resistivity measurements have been performed on a low (LR)- and high (HR)-resistance variant of the kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br superconductor. While the HR sample was synthesized following the standard procedure, the LR crystal is a result of a somewhat modified synthesis route. According to their residual resistivities and residual resistivity ratios, the LR crystal is of distinctly superior quality. He-gas pressure was used to study the effect of hydrostatic pressure on the different...
Source: http://arxiv.org/abs/cond-mat/0407478v1

Arxiv.org

81 81

Incoherent Interplane Conductivity of kappa-(BEDT-TTF)2Cu[N(CN)2]Br

Sep 24, 2013 09/13

by J. J. McGuire; T. Room; A. Pronin; T. Timusk; J. A. Schlueter; M. E. Kelly; A. M. Kini

eye 81

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The interplane optical spectrum of the organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br was investigated in the frequency range from 40 to 40,000 cm-1. The optical conductivity was obtained by Kramers-Kronig analysis of the reflectance. The absence of a Drude peak at low frequency is consistent with incoherent conductivity but in apparent contradiction to the metallic temperature dependence of the DC resistivity. We set an upper limit to the interplane transfer integral of tb = 0.1 meV. A...
Source: http://arxiv.org/abs/cond-mat/0103237v1

Arxiv.org

55 55

Test for interlayer coherence in a quasi-two-dimensional superconductor

Sep 21, 2013 09/13

by John Singleton; P. A. Goddard; A. Ardavan; N. Harrison; S. J. Blundell; J. A. Schlueter; A. M. Kini

eye 55

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Peaks in the magnetoresistivity of the layered superconductor $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$, measured in fields $\leq 45$ T applied within the layers, show that the Fermi surface is extended in the interlayer direction and enable the interlayer transfer integral ($t_{\perp} \approx 0.04$ meV) to be deduced. However, the quasiparticle scattering rate $\tau^{-1}$ is such that $\hbar/\tau \sim 6t_{\perp}$, implying that $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ meets the criterion used to identify...
Source: http://arxiv.org/abs/cond-mat/0104570v2

Arxiv.org

64 64

DC and high-frequency conductivity of the organic metals beta"-(BEDT-TTF)2SF5RSO3 (R = CH2CF2 and CHF)

Sep 18, 2013 09/13

by M. Glied; S. Yasin; S. Kaiser; N. Drichko; M. Dressel; J. Wosnitza; J. A. Schlueter; G. L. Gard

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The temperature dependences of the electric-transport properties of the two-dimensional organic conductors beta"-(BEDT-TTF)2SF5CH2CF2SO3, beta"-(d8-BEDT-TTF)2SF5CH2CF2SO3, and beta"-(BEDT-TTF)2SF5CHFSO3 are measured by dc methods in and perpendicular to the highly-conducting plane. Microwave measurements are performed at 24 and 33.5 GHz to probe the high-frequency behavior from room temperature down to 2 K. Superconductivity is observed in beta"-(BEDT-TTF)2SF5CH2CF2SO3 and...
Source: http://arxiv.org/abs/0809.2202v1

Arxiv.org

79 79

Spin-zero anomaly in the magnetic quantum oscillations of a two-dimensional metal

Sep 24, 2013 09/13

by J. Wosnitza; V. M. Gvozdikov; J. Hagel; P. J. Meeson; J. A. Schlueter; R. W. Winter; G. L. Gard

eye 79

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We report on an anomalous behavior of the spin-splitting zeros in the de Haas-van Alphen (dHvA) signal of a quasi-two-dimensional organic superconductor. The zeros as well as the angular dependence of the amplitude of the second harmonic deviate remarkably from the standard Lifshitz-Kosevich (LK) prediction. In contrast, the angular dependence of the fundamental dHvA amplitude as well as the spin-splitting zeros of the Shubnikov-de Haas signal follow the LK theory. We can explain this behavior...
Source: http://arxiv.org/abs/cond-mat/0412202v1

Arxiv.org

3 3.0

$Lattice vibrations of the charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: novel interpretation of the electrodynamic response in a spin-liquid compound$

Lattice vibrations of the charge-transfer salt $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_{3}$: novel interpretation of the electrodynamic response in a spin-liquid compound

Jun 29, 2018 06/18

by M. Dressel; P. Lazic; A. Pustogow; E. Zhukova; B. Gorshunov; J. A. Schlueter; O. Milat; B. Gumhalter; S. Tomic

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The dimer Mott insulator $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ exhibits unusual electrodynamic properties. Numerical investigations of the electronic ground state and the molecular and lattice vibrations reveal the importance of the Cu$_2$(CN)$_3^-$ anion network coupled to the BEDT-TTF molecules: The threefold cyanide coordination of copper and linkage isomerism in the anion structure cause a loss of symmetry, frustration, disorder, and domain formation. Our findings consistently explain the...
Topics: Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1601.04926

Arxiv.org

77 77

Angle Dependent Magnetoresistance of the Layered Organic Superconductor κ-(ET)2Cu(NCS)2: Simulation and Experiment

Sep 23, 2013 09/13

by P. A. Goddard; S. J. Blundell; J. Singleton; R. D. McDonald; A. Ardavan; A. Narduzzo; J. A. Schlueter; A. M. Kini; T. Sasaki

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The angle-dependences of the magnetoresistance of two different isotopic substitutions (deuterated and undeuterated) of the layered organic superconductor \kappa-(ET)2Cu(NCS)2 are presented. The angle dependent magnetoresistance oscillations (AMRO) arising from the quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces in this material are often confused. By using the Boltzman transport equation extensive simulations of the AMRO are made that reveal the subtle differences...
Source: http://arxiv.org/abs/cond-mat/0312197v1

Arxiv.org

49 49

$Thermal activation between Landau levels in the organic superconductor $β''$-(BEDT-TTF)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$$

Thermal activation between Landau levels in the organic superconductor $β''$-(BEDT-TTF)$_{2}$SF$_{5}$CH$_{2}$CF$_{2}$SO$_{3}$

Sep 18, 2013 09/13

by M. -S. Nam; A. Ardavan; J. A. Symington; J. Singleton; N. Harrison; C. H. Mielke; J. A. Schlueter; R. W. Winter; G. L. Gard

eye 49

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We show that Shubnikov-de Haas oscillations in the interlayer resistivity of the organic superconductor $\beta''$-(BEDT-TTF)$_{2}$SF$_{5}$ CH$_{2}$CF$_{2}$SO$_{3}$ become very pronounced in magnetic fields $\sim$~60~T. The conductivity minima exhibit thermally-activated behaviour that can be explained simply by the presence of a Landau gap, with the quasi-one-dimensional Fermi surface sheets contributing negligibly to the conductivity. This observation, together with complete suppression of...
Source: http://arxiv.org/abs/cond-mat/0105048v1

Arxiv.org

53 53

Muon-fluorine entangled states in molecular magnets

Sep 18, 2013 09/13

by T. Lancaster; S. J. Blundell; P. J. Baker; M. L. Brooks; W. Hayes; F. L. Pratt; J. L. Manson; M. M. Conner; J. A. Schlueter

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The information accessible from a muon-spin relaxation experiment is often limited since we lack knowledge of the precise muon stopping site. We demonstrate here the possibility of localizing a spin polarized muon in a known stopping state in a molecular material containing fluorine. The muon-spin precession that results from the entangled nature of the muon-spin and surrounding nuclear spins is sensitive to the nature of the stopping site and we use this property to identify three classes of...
Source: http://arxiv.org/abs/0707.2761v1

Arxiv.org

32 32

Doping and Irradiation Controlled Vortex Pinning Behavior in BaFe2(As1-xPx)2 Single Crystals

Sep 21, 2013 09/13

by L. Fang; Y. Jia; J. A. Schlueter; A. Kayani; Z. L. Xiao; H. Claus; U. Welp; A. E. Koshelev; G. W. Crabtree; W. -K. Kwok

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We report on the systematic evolution of vortex pinning behavior in isovalent doped single crystals of BaFe2(As1-xPx)2. Proceeding from optimal doped to ovedoped samples, we find a clear transfor- mation of the magnetization hysteresis from a fishtail behavior to a distinct peak effect followed by a reversible magnetization and Bean Livingston surface barriers. Strong point pinning dominates the vortex behavior at low fields whereas weak collective pinning determines the behavior at higher...
Source: http://arxiv.org/abs/1106.2599v2

Arxiv.org

58 58

Angle-dependent magnetoresistance oscillations due to magnetic breakdown orbits

Sep 22, 2013 09/13

by A. F. Bangura; P. A. Goddard; J. Singleton; S. W. Tozer; A. I. Coldea; A. Ardavan; R. D. McDonald; S. J. Blundell; J. A. Schlueter

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We present experimental evidence for a hitherto unconfirmed type of angle-dependent magnetoresistance oscillation caused by magnetic breakdown. The effect was observed in the organic superconductor kappa-(BEDT-TTF)$_2$Cu(NCS)$_2$ using hydrostatic pressures of up to 9.8 kbar and magnetic fields of up to 33 T. In addition, we show that similar oscillations are revealed in ambient pressure measurements, provided that the Shubnikov-de Haas oscillations are suppressed either by elevated...
Source: http://arxiv.org/abs/cond-mat/0702570v2

Arxiv.org

61 61

Coherent vs incoherent interlayer transport in layered metals

Sep 21, 2013 09/13

by J. Wosnitza; J. Hagel; J. S. Qualls; J. S. Brooks; E. Balthes; D. Schweitzer; J. A. Schlueter; U. Geiser; J. Mohtasham; R. W. Winter; G. L. Gard

eye 61

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The magnetic-field, temperature, and angular dependence of the interlayer magnetoresistance of two different quasi-two-dimensional (2D) organic superconductors is reported. For $\kappa$-(BEDT-TTF)$_2$I$_3$ we find a well-resolved peak in the angle-dependent magnetoresistance at $\Theta = 90^\circ$ (field parallel to the layers). This clear-cut proof for the coherent nature of the interlayer transport is absent for $\beta$''-(BEDT-TTF)$_2$SF$_5$CH$_2$CF$_2$SO$_3$. This and the non-metallic...
Source: http://arxiv.org/abs/cond-mat/0203567v1

Arxiv.org

45 45

Anomalous superfluid density in quantum critical superconductors

Sep 22, 2013 09/13

by K. Hashimoto; Y. Mizukami; R. Katsumata; H. Shishido; M. Yamashita; H. Ikeda; Y. Matsuda; J. A. Schlueter; J. D. Fletcher; A. Carrington; D. Gnida; D. Kaczorowski; T. Shibauchi

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When a second-order magnetic phase transition is tuned to zero temperature by a non-thermal parameter, quantum fluctuations are critically enhanced, often leading to the emergence of unconventional superconductivity. In these `quantum critical' superconductors it has been widely reported that the normal-state properties above the superconducting transition temperature $T_c$ often exhibit anomalous non-Fermi liquid behaviors and enhanced electron correlations. However, the effect of these strong...
Source: http://arxiv.org/abs/1302.2945v1

Arxiv.org

43 43

High field magnetic resonant properties of beta'-(ET)2SF5CF2SO3

Sep 19, 2013 09/13

by I. B. Rutel; S. A. Zvyagin; J. S. Brooks; J. Krzystek; P. Kuhns; A. P. Reyes; B. H. Ward; J. A. Schlueter; R. W. Winter; G. L. Gard

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A systematic electron spin resonance (ESR) investigation of the low temperature regime for the (ET)2SF5CF2SO3 system was performed in the frequency range of ~200-700 GHz, using backward wave oscillator sources, and at fields up to 25 T. Newly acquired access to the high frequency and fields shows experimental ESR results in agreement with the nuclear magnetic resonance (NMR) investigation, revealing evidence that the transition seen at 20 K is not of conventional spin-Peierls order. A...
Source: http://arxiv.org/abs/cond-mat/0209295v4

Arxiv.org

50 50

Field-induced metal-insulator transition in a two-dimensional organic superconductor

Sep 22, 2013 09/13

by J. Wosnitza; S. Wanka; J. Hagel; H. v. Loehneysen; J. S. Qualls; J. S. Brooks; E. Balthes; J. A. Schlueter; U. Geiser; J. Mohtasham; R. W. Winter; G. L. Gard

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The quasi-two-dimensional organic superconductor beta-(BEDT-TTF)_2SF_5CH_2CF_2SO_3 (T_c approx 4.4 K)shows very strong Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, R_b. Comparison with de Haas- van Alphen oscillations allow a reliable estimate of R_b which is crucial for the correct extraction of the SdH signal. At low temperatures and high magnetic fields insulating behavior evolves. The magnetoresistance data violate...
Source: http://arxiv.org/abs/cond-mat/0011357v1

Arxiv.org

4 4.0

$Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$$

Anisotropic charge dynamics in the quantum spin-liquid candidate $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$

Jun 30, 2018 06/18

by M. Pinteric; M. Culo; O. Milat; M. Basletic; B. Korin-Hamzic; E. Tafra; A. Hamzic; T. Ivek; T. Peterseim; K. Miyagawa; K. Kanoda; J. A. Schlueter; M. Dressel; S. Tomic

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We have in detail characterized the anisotropic charge response of the dimer Mott insulator $\kappa$-(BEDT-TTF)$_2$\-Cu$_2$(CN)$_3$ by dc conductivity, Hall effect and dielectric spectroscopy. At room temperature the Hall coefficient is positive and close to the value expected from stoichiometry; the temperature behavior follows the dc resistivity $\rho(T)$. Within the planes the dc conductivity is well described by variable-range hopping in two dimensions; this model, however, fails for the...
Topics: Strongly Correlated Electrons, Condensed Matter
Source: http://arxiv.org/abs/1407.6252

Arxiv.org

109 109

Evolution of magnetic interactions in a pressure-induced Jahn-Teller driven magnetic dimensionality switch

Jul 20, 2013 07/13

by S. Ghannadzadeh; J. S. Möller; P. A. Goddard; T. Lancaster; F. Xiao; S. J. Blundell; A. Maisuradze; R. Khasanov; J. L. Manson; S. W. Tozer; D. Graf; J. A. Schlueter

eye 109

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We present the results of high-field magnetization and muon-spin relaxation measurements on the coordination polymer CuF_2(H_2O)_2(pyrazine) in pressures up to 22.5 kbar. We observe a transition from a quasi-two-dimensional to a quasi-one-dimensional antiferromagnetic phase at 9.1 kbar, driven by a rotation of the Jahn-Teller axis. Long-range antiferromagnetic ordering is seen in both regimes, as well as a phase separation in the critical pressure region. The magnetic dimensionality switching...
Source: http://arxiv.org/abs/1304.5403v1

Arxiv.org

60 60

Exchange parameters of copper-based quasi-two-dimensional Heisenberg magnets measured using high magnetic fields and muon-spin rotation

Sep 18, 2013 09/13

by P. A. Goddard; J. Singleton; P. Sengupta; R. D. McDonald; T. Lancaster; S. J. Blundell; F. L. Pratt; S. Cox; N. Harrison; J. L. Manson; H. I. Southerland; J. A. Schlueter

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Pulsed-field magnetization experiments (fields $B$ of up to 85 T and temperatures $T$ down to 0.4 K) are reported on nine organic Cu-based two-dimensional (2D) Heisenberg magnets. All compounds show a low-$T$ magnetization that is concave as a function of $B$, with a sharp ``elbow'' transition to a constant value at a field $B_{\rm c}$. Monte-Carlo simulations including a finite interlayer exchange energy $J_{\perp}$ quantitatively reproduce the data; the concavity indicates the effective...
Source: http://arxiv.org/abs/0803.4169v1

Arxiv.org

37 37

Isotope effect in quasi-two-dimensional metal-organic antiferromagnets

Sep 17, 2013 09/13

by P. A. Goddard; J. Singleton; C. Maitland; S. J. Blundell; T. Lancaster; P. J. Baker; R. D. McDonald; S. Cox; P. Sengupta; J. L. Manson; K. A. Funk; J. A. Schlueter

eye 37

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Although the isotope effect in superconducting materials is well-documented, changes in the magnetic properties of antiferromagnets due to isotopic substitution are seldom discussed and remain poorly understood. This is perhaps surprising given the possible link between the quasi-two-dimensional (Q2D) antiferromagnetic and superconducting phases of the layered cuprates. Here we report the experimental observation of shifts in the N\'{e}el temperature and critical magnetic fields ($\Delta T_{\rm...
Source: http://arxiv.org/abs/0807.1506v2

Arxiv.org

54 54

An Experimental and Semi-Empirical Method to Determine the Pauli-Limiting Field in Quasi 2D Superconductors as applied to $κ$-(BEDT-TTF)$_2$Cu(NCS)$_2$: Strong Evidence of a FFLO State

Sep 23, 2013 09/13

by C. C. Agosta; Jing Jin; W. A. Coniglio; B. E. Smith; K. Cho; I. Stroe; C. Martin; S. W. Tozer; T. P. Murphy; E. C. Palm; J. A. Schlueter; M. Kurmoo

eye 54

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We present upper critical field data for $\kappa$-(BEDT-TTF)$_2$Cu(NCS)$_2$ with the magnetic field close to parallel and parallel to the conducting layers. We show that we can eliminate the effect of vortex dynamics in these layered materials if the layers are oriented within 0.3 degrees of parallel to the applied magnetic field. Eliminating vortex effects leaves one remaining feature in the data that corresponds to the Pauli paramagnetic limit ($H_p$). We propose a semi-empirical method to...
Source: http://arxiv.org/abs/1111.5025v3

Arxiv.org

80 80

Magnetically driven metal-insulator transition in NaOsO3

Sep 23, 2013 09/13

by S. Calder; V. O. Garlea; D. F. McMorrow; M. D. Lumsden; M. B. Stone; J. C. Lang; J. -W. Kim; J. A. Schlueter; Y. G. Shi; K. Yamaura; Y. S. Sun; Y. Tsujimoto; A. D. Christianson

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The metal-insulator transition (MIT) is one of the most dramatic manifestations of electron correlations in materials. Various mechanisms producing MITs have been extensively considered, including the Mott (electron localization via Coulomb repulsion), Anderson (localization via disorder) and Peierls (localization via distortion of a periodic 1D lattice). One additional route to a MIT proposed by Slater, in which long-range magnetic order in a three dimensional system drives the MIT, has...
Source: http://arxiv.org/abs/1202.1482v1

Arxiv.org

63 63

Magnetic order in the S=1/2 two-dimensional molecular antiferromagnet, copper pyrazine perchlorate Cu(Pz)_2(ClO_4)_2

Sep 20, 2013 09/13

by T. Lancaster; S. J. Blundell; M. L. Brooks; P. J. Baker; F. L. Pratt; J. L. Manson; M. M. Conner; F. Xiao; C. P. Landee; F. A. Chaves; S. Soriano; M. A. Novak; T. Papageorgiou; A. Bianchi; T. Herrmannsdorfer; J. Wosnitza; J. A. Schlueter

eye 63

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We present an investigation of magnetic ordering in the two-dimensional S=1/2 quantum magnet Cu(Pz)_2(ClO_4)_2 using specific heat and zero field muon-spin relaxation (\mu^+SR). The magnetic contribution to the specific heat is consistent with an exchange strength of 17.7(3) K. We find unambiguous evidence for a transition to a state of three-dimensional long range order below a critical temperature T_N=4.21(1) K using \mu^+SR even though there is no feature in the specific heat at that...
Source: http://arxiv.org/abs/cond-mat/0612317v1

Arxiv.org

5 5.0

Control of the third dimension in copper-based square-lattice antiferromagnets

Jun 29, 2018 06/18

by Paul A. Goddard; John Singleton; Isabel Franke; Johannes S. Moller; Tom Lancaster; Andrew J. Steele; Craig V. Topping; Stephen J. Blundell; Francis L. Pratt; C. Baines; Jesper Bendix; Ross D. McDonald; Jamie Brambleby; Martin R. Lees; Saul H. Lapidus; Peter W. Stephens; Brendan W. Twamley; Marianne M. Conner; Kylee Funk; Jordan F. Corbey; Hope E. Tran; J. A. Schlueter; Jamie L. Manson

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Using a mixed-ligand synthetic scheme, we create a family of quasi-two-dimensional antiferromagnets, namely, [Cu(HF$_2$)(pyz)$_2$]ClO$_4$ [pyz = pyrazine], [Cu$L_2$(pyz)$_2$](ClO$_4$)$_2$ [$L$ = pyO = pyridine-N-oxide and 4-phpyO = 4-phenylpyridine-N-oxide. These materials are shown to possess equivalent two-dimensional [Cu(pyz)$_2$]$^{2+}$ nearly square layers, but exhibit interlayer spacings that vary from 6.5713~\AA ~to 16.777~\AA, as dictated by the axial ligands. We present the structural...
Topics: Mesoscale and Nanoscale Physics, Condensed Matter, Strongly Correlated Electrons
Source: http://arxiv.org/abs/1603.00355

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