Low-Temperature Heat Capacity Anomalies in Ordered and Disordered Phases of Normal and Deuterated Thiophene.

We measured the specific heat of normal (CHS) and deuterated (CDS) thiophene in the temperature interval of 1 ≤ , K ≤ 25. CHS exhibits a metastable phase II and a stable phase V, both with frozen orientational disorder (OD), whereas CDS exhibits a metastable phase II, which is analogous to the OD phase II of CHS and a fully ordered stable phase V. Our measurements demonstrate the existence of a large bump in the heat capacity of both stable and metastable CDS and CHS phases at temperatures of ∼10 K, which significantly departs from the expected Debye temperature behavior of ≈ .

Selective detection of complex gas mixtures using point contacts: concept, method and tools.

Of all modern nanosensors using the principle of measuring variations in electric conductance, point-contact sensors stand out in having a number of original sensor properties not manifested by their analogues. The nontrivial nature of point-contact sensors is based on the unique properties of Yanson point contacts used as the sensing elements. The quantum properties of Yanson point contacts enable the solution of some of the problems that could not be solved using conventional sensors measuring conductance.

Analog of a Quantum Heat Engine Using a Single-Spin Qubit.

A quantum two-level system with periodically modulated energy splitting could provide a minimal universal quantum heat machine. We present the experimental realization and the theoretical description of such a two-level system as an impurity electron spin in a silicon tunnel field-effect transistor. In the incoherent regime, the system can behave analogously to either an Otto heat engine or a refrigerator.

Adsorption of Polyadenylic acid on graphene oxide: experiments and computer modeling.

In this work, we study the adsorption of poly(rA) on graphene oxide (GO) using AFM and UV absorption spectroscopies. A transformation of the homopolynucleotide structure on the GO surface is observed. It is found that an energetically favorable conformation of poly(rA) on GO is achieved after a considerable amount of time (days).

Ultra-fast vortex motion in a direct-write Nb-C superconductor.

The ultra-fast dynamics of superconducting vortices harbors rich physics generic to nonequilibrium collective systems. The phenomenon of flux-flow instability (FFI), however, prevents its exploration and sets practical limits for the use of vortices in various applications. To suppress the FFI, a superconductor should exhibit a rarely achieved combination of properties: weak volume pinning, close-to-depairing critical current, and fast heat removal from heated electrons.

Phase Transitions in the Metastable Perovskite Multiferroics BiCrO and BiCrScO: A Comparative Study.

The temperature behavior of the crystal structure as well as dielectric and magnetic properties of the perovskite bismuth chromate ceramics with the 10 mol % Cr-to-Sc substitution were studied and compared with those of the unmodified compound. Using a high-pressure synthesis, BiCrO and BiCrScO were obtained as metastable perovskite phases which are monoclinic 2/ with the √6 × √2 × √6 superstructure (where is the primitive perovskite unit-cell parameter) under ambient conditions. At room temperature, the unit cell volume of BiCrScO is ∼1.

Magnetic anisotropy in CsGd(MoO)probed by EPR spectroscopy.

Here we report electron paramagnetic resonance (EPR) study of rare-earth paramagnet CsGd(MoO). Multifrequency EPR measurements allowed us to directly probe the splitting of the lowestSmultiplet of Gdion and revealed the rhombic type of single-ion anisotropy. An easy-axis anisotropy approximation with a rhombic distortion of the Gdlocal environment describes obtained EPR spectra and yield energies ofSsplitting.

Peculiarities of pseudogap in YPrBaCuO single crystals under pressure up to 1.7 GPa.

The effect of hydrostatic pressure up to P = 1.7 GPa on the fluctuation conductivity σ'(T) and pseudogap ∆*(T) in YPrBaCuO single crystal with critical temperature Т = 85.2 K (at P = 0) was investigated.

Synthesis and Magnetic Properties of the KCu(IO) Compound with [CuO] Chains.

The new quaternary iodate KCu(IO) has been prepared by hydrothermal synthesis. KCu(IO) crystallizes in the monoclinic space group 2/ with unit cell parameters = 9.8143(4) Å, = 8.

Quantum Interferometry with a g-Factor-Tunable Spin Qubit.

We study quantum interference effects of a qubit whose energy levels are continuously modulated. The qubit is formed by an impurity electron spin in a silicon tunneling field-effect transistor, and it is read out by spin blockade in a double-dot configuration. The qubit energy levels are modulated via its gate-voltage-dependent g factors, with either rectangular, sinusoidal, or ramp radio frequency waves.

Comment on "High-Pressure Behavior of Hydrogen and Deuterium at Low Temperatures".

X.-D. Liu et al.

Dielectric resonator method for determining gap symmetry of superconductors through anisotropic nonlinear Meissner effect.

We present a new measurement method which can be used to image the gap nodal structure of superconductors whose pairing symmetry is under debate. This technique utilizes a high quality factor microwave resonance involving the sample of interest. While supporting a circularly symmetric standing wave current pattern, the sample is perturbed by a scanned laser beam, creating a photoresponse that was previously shown to reveal the superconducting gap anisotropy.

Simulating quantum dynamical phenomena using classical oscillators: Landau-Zener-Stückelberg-Majorana interferometry, latching modulation, and motional averaging.

A quantum system can be driven by either sinusoidal, rectangular, or noisy signals. In the literature, these regimes are referred to as Landau-Zener-Stückelberg-Majorana (LZSM) interferometry, latching modulation, and motional averaging, respectively. We demonstrate that these pronounced and interesting effects are also inherent in the dynamics of classical two-state systems.

Microstructure and Mechanical Properties of High-Entropy Alloy CoCrFeMnNi Processed by High-Pressure Torsion at 77 K and 300 K.

In this work, the mechanical characteristics of high-entropy alloy CoCrFeMnNi with low-stacking fault energy processed by cryogenic and room temperature high-pressure torsion (HPT) were studied. X-ray diffraction, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were performed to identify the phase and microstructure variation and the mechanical properties characterized by Vickers hardness measurements and tensile testing. Cryogenic HPT was found to result in a lower mechanical strength of alloy CoCrFeMnNi than room temperature HPT.

Spin-glass polyamorphism induced by a magnetic field in LaMnO single crystal.

We present experimental evidence of field-driven transition in spin-glass state, similar to pressure-induced transition between amorphous phases in structural and metallic glasses, attributed to the polyamorphism phenomena. Cusp in temperature dependences of ac magnetic susceptibility of weakly disordered LaMnO single crystal is registered below the temperature of magnetic ordering. Frequency dependence of the cusp temperature proves its spin-glass origin.

Glassy Anomalies in the Low-Temperature Thermal Properties of a Minimally Disordered Crystalline Solid.

The low-temperature thermal and transport properties of an unusual kind of crystal exhibiting minimal molecular positional and tilting disorder have been measured. The material, namely, low-dimensional, highly anisotropic pentachloronitrobenzene has a layered structure of rhombohedral parallel planes in which the molecules execute large-amplitude in-plane as well as concurrent out-of-plane librational motions. Our study reveals that low-temperature glassy anomalies can be found in a system with minimal disorder due to the freezing of (mostly in-plane) reorientational jumps of molecules between equivalent crystallographic positions with partial site occupation.

Interaction of a tricationic meso-substituted porphyrin with guanine-containing polyribonucleotides of various structures.

The interaction of a tricationic water-soluble meso-(N-methylpyridinium)-substituted porphyrin, TMPyP, derived from classic TMPyP4, with double-stranded poly(G)  ⋅  poly(C) and four-stranded poly(G) polyribonucleotides has been studied in aqueous buffered solutions, pH 6.9, of low and near-physiological ionic strengths in a wide range of molar phosphate-to-dye ratios (P/D). To clarify the binding modes of TMPyP to biopolymers various spectroscopic techniques, including absorption and polarized fluorescence spectroscopy, Raman spectroscopy, and resonance light scattering, were used.

Thermodynamic and Kinetic Fragility of Freon 113: The Most Fragile Plastic Crystal.

We present a dynamic and thermodynamic study of the orientational glass former Freon 113 (1,1,2-trichloro-1,2,2-trifluoroethane, CCl_{2}F-CClF_{2}) in order to analyze its kinetic and thermodynamic fragilities. Freon 113 displays internal molecular degrees of freedom that promote a complex energy landscape. Experimental specific heat and its microscopic origin, the vibrational density of states from inelastic neutron scattering, together with the orientational dynamics obtained by means of dielectric spectroscopy have revealed the highest fragility value, both thermodynamic and kinetic, found for this orientational glass former.

Terahertz lattice dynamics of the potassium rare-earth binary molybdates.

We report a systematic study of low-energy lattice vibrations in the layered systems KY(MoO), KDy(MoO), KEr(MoO), and KTm(MoO). A layered crystal structure and low symmetry of the local environment of the rare-earth ion cause the appearance of vibrational and electronic excitations in Terahertz frequencies. The interaction between these excitations leads to sophisticated dynamical properties, including non-linear effects in paramagnetic resonance spectra.

Nanoelectromechanical Heat Engine Based on Electron-Electron Interaction.

We theoretically show that a nanoelectromechanical system can be mechanically actuated by a heat flow through it via an electron-electron interaction. In contrast to most known actuation mechanisms in similar systems, this new mechanism does not involve an electronic current nor external ac fields. Instead, the mechanism relies on deflection-dependent tunneling rates and a heat flow which is mediated by an electron-electron interaction while an electronic current through the device is prohibited by, for instance, a spin-valve effect.

Probing the Influence of Amino Acids on Photoluminescence from Carbon Nanotubes Suspended with DNA.

The quantitative analysis of amino acid levels in the human organism is required for the early clinical diagnosis of a variety of diseases. In this work the influence of 13 amino acid doping on the photoluminescence (PL) from the semiconducting single-walled carbon nanotubes (SWNTs) suspended with single-stranded DNA (ssDNA) in water has been studied. Amino acid doping leads to the PL enhancement and the strongest increase was found after cysteine doping of the nanotube suspension while addition of other amino acids yielded the significantly smaller effect.

The effect of protonation of cytosine and adenine on their interactions with carbon nanotubes.

Placing electrical charges on nanomaterials is a means to extend their functional capabilities in nanoelectronics and sensoring applications. This paper explores the effect of charging nitrogen bases cytosine (Cyt) and adenine (Ade) via protonation on their noncovalent interaction with carbon nanotubes (CNT) using quantum chemical calculations performed at the M05-2X/6-31++G** level of theory alongside with a molecular graphics method. It is shown that the protonation of the bases causes threefold increase of the interaction energy in the CNT·Cyt·H and СNT·Ade·H complexes as compared to the CNT complexes formed with neutral bases.

Spin-mediated Photomechanical Coupling of a Nanoelectromechanical Shuttle.

We show that nanomechanical vibrations in a magnetic shuttle device can be strongly affected by external microwave irradiation through photo-assisted electronic spin-flip transitions. Mechanical consequences of these spin flips are due to a spin-dependent magnetic force, which may lead to a nanomechanical instability in the device. We derive a criterion for the instability to occur and analyze different regimes of nanomechanical oscillations.

Memristive Sisyphus circuit for clock signal generation.

Frequency generators are widely used in electronics. Here, we report the design and experimental realization of a memristive frequency generator employing a unique combination of only digital logic gates, a single-supply voltage and a realistic thresholdtype memristive device. In our circuit, the oscillator frequency and duty cycle are defined by the switching characteristics of the memristive device and external resistors.

Thermal Conductivity of Triphenyl Phosphite's Liquid, Glassy, and Glacial States.

The thermal conductivity κ and heat capacity per unit volume ρCp of triphenyl phosphite (TPP) were measured under different pressure and temperature conditions, and with time during the sluggish liquid to glacial state transformation at temperatures about 15 K above the glass transition temperature. As the transformation slowly proceeds during several hours, ρCp decreases monotonically from that of the liquid state to a value close to that of the vitrified state. Concurrently, κ increases nonmonotonically with an intermediate local maximum followed by a minimum, before the final rise to a higher κ.