Quantum spin liquid state

Keywords Charge transfer solid Electronic dimensionality Functional organic solid Ionicity diagram Organic metal Organic superconductor Phase transition Quantum spin liquid state Switching... 

Spin Disordered State (Quantum Spin Liquid State) Neighboring Superconductivity. .. 103... 

New Spin State Originated from Strong Spin Frustrations Quantum Spin Liquid State... 

Figure 17c,d compares the line shapes of NMR absorption of k-(ET)2 Cu2(CN)3 and k-(ET)2Cu[N(CN)2]C1, respectively. K-(ET)2Cu[N(CN)2]a exhibited a drastic change below 27 K owing to the formation of three-dimensional AF ordering, while, the absorption band of k-(ET)2Cu2(CN)3 remained almost invariant down to 32 mK, indicating a nonspin-ordered state the quantum spin liquid state [342, 349-357]. 

Following ic-(ET)2Cu2(CN)3, five materials [364], including EtMe3Sb[Pd (dmit)2]2 as an organic solid [365], have been found to have quantum spin liquid states however, superconductivity has been confirmed only for k-(ET)2Cu2(CN)3. 

Yamashita M, Nakata N, Kasahara Y, Sasaki T, Yoneyama N, Kobayashi N, Fujimoto S, Shibauchi T, Matsuda Y (2009) Thermal-transport measurements in a quantum spin-liquid state of the frustrated triangular magnet k-(BEDT-TTF)2Cu2(CN)3. Nat Phys 5 44-47... 

Summary YbPdSb is magnetically unstable. The [xSR data on a sample that does not develop long-range AFM order show that the material enters a spin-liquid state instead. This state is characterized by dynamic short-range correlations whose fluctuation rate becomes temperature independent below 0.3 K at the comparatively low value of 60 MHz. Probably one deals with quantum fluctuations that are interpreted here as local moment fluctuations induced by the dynamics of fluctuating bonds of Kondo spin pairs. 

Liquid Helium-4. Quantum mechanics defines two fundamentally different types of particles bosons, which have no unpaired quantum spins, and fermions, which do have unpaired spins. Bosons are governed by Bose-Einstein statistics which, at sufficiently low temperatures, allow the particles to coUect into a low energy quantum level, the so-called Bose-Einstein condensation. Fermions, which include electrons, protons, and neutrons, are governed by Fermi-DHac statistics which forbid any two particles to occupy exactly the same quantum state and thus forbid any analogue of Bose-Einstein condensation. Atoms may be thought of as assembHes of fermions only, but can behave as either fermions or bosons. If the total number of electrons, protons, and neutrons is odd, the atom is a fermion if it is even, the atom is a boson. 

The multiple-quantum (MQ)/MAS NMR is one of the 2D NMR methods, which is capable of averaging out the second-order quadrupolar interaction in nuclei with spin > 1/2 such as H, "B, O, etc. The "B MQ/ MAS NMR measurements on boron as contained in silyl-carborane hybrid Si-based polymer networks considered here. The molded samples are cut into small pieces to insert them into a 4-mm NMR rotor and spun at 12 kHz in a MAS probe. The observation frequency of the "B nucleus (spin number I = 3/2 and isotope natural abundance = 80.42%) is 96.3 MHz. Excitation of both the echo (—3Q) and anti echo (+3Q) coherences is achieved by using a three-pulse sequence with a zero quantum filter (z-filter). The widths of the first, second, and third pulses are 3.0 4.1 ps, 1.1-1.6 ps, and 19-28 ps, respectively. The z-filter is 20 ps. The recycle delay time is 6-15 s and the data point of FI (vertical) axis is 64 and for each the number of scans is 144. Then, the total measurement time is 15-38 h. The phase cycling used in this experiment consists of 12 phases. Boron phosphate (BPO4 3 = 0 ppm) is used as an external standard for "B. The chemical shift value of BPO4 is —3.60 ppm from BF3 O(C2H5)2 which is used as a standard reference in " B NMR in the liquid state. The transmitter frequency of " B is set on peak of BPO4 for a trustworthy chemical shift after Fourier transform." " ... 

With the aim of quantitatively predicting the orientational order of rigid solutes of small dimensions dissolved in the nematic liquid crystal solvent, 4-n-pentyl-4 cyanobiphenyl (5CB), an atomistic molecular dynamics (MD) computer simulation has been applied. It is found that for the cases examined the alignment mechanism is dominated by steric and van der Waals dispersive forces. A computer simulation of the deuterium NMR spectra of molecules in a thin nematic cell has been carried out and the director distribution in the cell has been studied. An experiment for the direct estimation of an element of the order matrix from H NMR spectra of strongly dipolar coupled spins that is based on the multiple quantum spin state selected detection of single quantum transitions has been proposed. The experiment also enables obtaining nearly accurate starting dipolar... 

In the previous section we have described some very ingenious proposals which, if implemented in practice, could lead to a large scale quantum information processor through NMR. It is important to emphasize that those proposals circumvent the scaling problem present in liquid-state NMR QIP experiments. However, whatever the sample architecture may be, it seems unavoidable the need to detect the NMR signal of very small spin concentrations. Ideally, single spin detection should be possible. Less than two decades ago, such a strict demand could sound hopeless conventional ESR needs a concentration of some... 

Fourier spectroscopy has unified solid- and liquid-state NMR in an unprecedented manner. Despite the fact that the principles of the techniques are the same, there are several factors causing significant differences between spectra of solids and liquids. The Hamiltonian, H, i.e. the quantum mechanical description of the various interactions experienced by a nuclear spin system, is given by... 

The product operator formalism has been used to analyse most liquid-state NMR experiments since it was first introduced in 1983. The examples given here have been chosen either because of the way in which they exemplify the manipulation of product operators or because the pulse sequences concerned play an important role in contemporary NMR spectroscopy. The spin echo is considered because of its wide use and the opportunity it presents to undertake a relatively simple product operator calculation in full without resort to any of the short cuts that will be used to simplify later calculations. COSY (correlation spectroscopy) is also a widely used experiment and allows the introduction of the concept of coherence transfer, and its double-quantum filtered variant exemplifies some important points about how... 

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