Stability and electronic properties of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">Sn</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">P</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>

Huang, Mengjie; Feng, Yuan Ping

doi:10.1103/physrevb.70.184116

Cited by 37 publications

(66 citation statements)

References 33 publications

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“…The recent activities in probing the physical behaviour of the compound series Na x CoO 2 (0.3 < x < 1) revealed a number of exciting features with respect to structural, electronic, magnetic and superconducting properties upon varying x [1,2,3,4,5,6,7,8]. Quite generally these compounds may be regarded as composed of stacks of alternating Na and Co-O layers.…”

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Melting of the Na Layers in SolidNa0.8CoO2

et al. 2009

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Data of23 Na NMR spectra-and relaxation measurements are interpreted as suggesting that, upon increasing temperature the Na layers in Na0.8CoO2 adopt a 2D liquid state at T = 291 K. The corresponding first order phase transition is preceded by a rapidly increasing mobility and diffusion of Na ions above 200 K. Above 291 K the 23 Na NMR response is similar to that previously observed in superionic conductors with planar Na layers.PACS numbers: 71.27.+a, 75.20.Hr, The recent activities in probing the physical behaviour of the compound series Na x CoO 2 (0.3 < x < 1) revealed a number of exciting features with respect to structural, electronic, magnetic and superconducting properties upon varying x [1,2,3,4,5,6,7,8]. Quite generally these compounds may be regarded as composed of stacks of alternating Na and Co-O layers. The role of the Na layers and the x dependence of the Na-ion arrangements have been discussed in detail [5,9]. The itinerant electronic and the magnetic degrees of freedom are concentrated in the Co-O layers [10]. Depending on the value of the Na concentration x, different ground states were identified. In this work we report a detailed 23 Na NMR investigation of the compound Na 0.8 CoO 2 . As we outline below our data are to some extent in conflict with previously published details of structural features of the Na sublattice, in particular if x < 1 [5]. Results of diffraction experiments were discussed in relation with models describing selected static vacancy arrangements [5,9]; aspects of the motion of Na-ions have been addressed to a much lesser extent [6,11]. Our results give clear evidence that the dynamics of the Na ions is a dominating factor for the understanding of these compounds at temperatures exceeding 200 K where a growing diffusion of the Na-ions sets in. Upon increasing temperature, this motion leads to a first order phase transition, most likely indicating the melting of the 2D layers of the Na sublattice at 291 K.The 23 Na nuclear magnetic resonance (NMR) experiments probed a 10.3 mg single crystalline specimen of Na x CoO 2 (x = 0.80(1)). Results of X-ray diffraction experiments confirmed the high structural quality of the sample and a quantitative chemical analysis of a specimen chosen from the same batch confirmed the Na concentration x. The crystal was characterised by magnetic susceptibility measurements using a commercial SQUID magnetometer. The NMR experiments were made in a commercial 4 He gas-flow cryostat, and the fixed external magnetic field B 0 = 7 T was provided by a commercial, ultra-shielded magnet. The 23 Na NMR spectra of the central line and the two quadrupolar satellites were separately obtained by fast Fourier transforming (FFT) the second half of the corresponding spin echo signals [18]. FIG. 1: Normalised23 Na NMR spectra of Na0.8CoO2 at different temperatures recorded in an external magnetic field of B0 = 7 T. a) Central line; b) Quadrupolar satellites measured on both sides of the central line. Their amplitudes are multiplied by a factor 5 with respect to ...

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Melting of the Na Layers in SolidNa0.8CoO2

et al. 2009

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“…Indeed, in recent NMR studies on Na 0.7 CoO 2 powder, various anomalies in the Na NMR spectrum were seen in a similar T range [24]. ple crystallographic phases or the presence of paramagnetic volume in otherwise magnetically ordered samples [25,26,27]. Here the actual process of phase separation is followed and the direct link to low temperature electronic instabilities is proven.…”

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“…in NMR in the form of inequivalent Co sites [12]. It was suggested from a theoretical point of view that sodium ordering at high temperatures [13,14,15] influences the electronic structure of the CoO 2 layers through Coulomb potential wells [15,16,17]. The key experimental challenge in this field is to establish the link between high-T sodium ordering and the low-T magnetic properties.…”

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Direct Link between Low-Temperature Magnetism and High-Temperature Sodium Order inNaxCoO2

et al. 2008

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“…The phase diagram of the cobaltate Na x CoO 2 · yH 2 O, with varying electron doping x and water intercalation y over a wide range, is very rich and complicated. In addition to superconductivity, it exhibits charge order, magnetic order including a metamagnetic transition, and other structural transitions [2,3,4,5]. The physics of these phases and the transitions among them is of importance by itself, and offers an excellent platform for studying correlated triangular lattice fermion systems.…”

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Fermi Surface Evolution and Luttinger Theorem inNaxCoO2: A Systematic Photoemission Study

et al. 2005

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We report a systematic angle-resolved photoemission study on NaxCoO2 for a wide range of Na concentrations (0.3 ≤ x ≤ 0.72). In all the metallic samples at different x, we observed (i) only a single hole-like Fermi surface centered around Γ and (ii) its area changes with x according to the Luttinger theorem. We also observed a surface state that exhibits a larger Fermi surface area. The e ′ g band and the associated small Fermi surface pockets near the K points predicted by band calculations are found to "sink" below the Fermi energy in a manner almost independent of the doping and temperature.The surprising discovery of superconductivity on Na x CoO 2 · yH 2 O [1] raises many interesting questions on the nature of pairing and its connection to the high-T c superconductivity. The phase diagram of the cobaltate Na x CoO 2 · yH 2 O, with varying electron doping x and water intercalation y over a wide range, is very rich and complicated. In addition to superconductivity, it exhibits charge order, magnetic order including a metamagnetic transition, and other structural transitions [2,3,4,5]. The physics of these phases and the transitions among them is of importance by itself, and offers an excellent platform for studying correlated triangular lattice fermion systems.Understanding the evolution of the low-energy electronic structure such as the quasiparticle (QP) dispersion and the Fermi surface (FS) topology is a necessary step toward understanding the diverse physical properties and the nature of the pairing interaction in this class of transition metal oxide. It is therefore important to gain the precise knowledge of the FS structure and the low-energy excitations in the unhydrated Na x CoO 2 which have been the focus in many recent theoretical and experimental efforts. The cobaltate is a multi-orbital system where the Co 4+ is in the 3d 5 configuration, occupying the lower t 2g band complex similar to the ruthenate Sr 2 RuO 4 . First principle band calculations have predicted that Na x CoO 2 has a large FS associated with the a 1g band centered around the Γ point and six small FS pockets of mostly e ′ g character near the K points for a wide range of x [6,7]. Based on this band structure, it has been proposed that the large density of states contribution from the six FS pockets and the nesting condition among them enhance the spin fluctuations and lead to superconducting pairing of the QPs on these FSs [8]. However, angle-resolved photoelectron spectroscopy (ARPES) measurements on the cobaltate with high Na concentrations (x ∼ 0.6 -0.7) revealed only the large FS [9,10]. It was also noticed that the enclosed FS area, i.e. the density of holes, may not satisfy the Luttinger theorem which is a fundamental QP counting rule in interacting electron systems. It is therefore desirable to study the evolution of the QP band dispersion and the FS, especially the fate of the FS pockets as a function of the Na concentration x. This is the focus of this work. We choose a set of metallic Na x CoO 2 with 0.3 ≤ x ≤ 0.72. The in...

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Stability and electronic properties ofSn3P4

Cited by 37 publications

References 33 publications

Melting of the Na Layers in SolidNa0.8CoO2

Melting of the Na Layers in SolidNa0.8CoO2

Direct Link between Low-Temperature Magnetism and High-Temperature Sodium Order inNaxCoO2

Fermi Surface Evolution and Luttinger Theorem inNaxCoO2: A Systematic Photoemission Study

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