The transition-metal-dichalcogenide family as a superconductor tuned by charge density wave strength.

In metallic transition metal dichalcogenides (TMDs), which remain superconducting down to single-layer thickness, the critical temperature T decreases for Nb-based, and increases for Ta-based materials. This contradicting trend is puzzling, impeding the development of a unified theory. Here we study the thickness-evolution of superconducting tunneling spectra in TaSheterostructures.

Utilising NV based quantum sensing for velocimetry at the nanoscale.

Nitrogen-Vacancy (NV) centers in diamonds have been shown in recent years to be excellent magnetometers on the nanoscale. One of the recent applications of the quantum sensor is retrieving the Nuclear Magnetic Resonance (NMR) spectrum of a minute sample, whose net polarization is well below the Signal-to-Noise Ratio (SNR) of classic devices. The information in the magnetic noise of diffusing particles has also been shown in decoherence spectroscopy approaches to provide a method for measuring different physical parameters.

Dynamical formation of a strongly correlated dark condensate of dipolar excitons.

Strongly interacting bosons display a rich variety of quantum phases, the study of which has so far been focused in the dilute regime, at a fixed number of particles. Here we demonstrate the formation of a dense Bose-Einstein condensate in a long-lived dark spin state of 2D dipolar excitons. A dark condensate of weakly interacting excitons is very fragile, being unstable against a coherent coupling of dark and bright spin states.

Spectroscopy of bulk and few-layer superconducting NbSe with van der Waals tunnel junctions.

Tunnel junctions, an established platform for high resolution spectroscopy of superconductors, require defect-free insulating barriers; however, oxides, the most common barrier, can only grow on a limited selection of materials. We show that van der Waals tunnel barriers, fabricated by exfoliation and transfer of layered semiconductors, sustain stable currents with strong suppression of sub-gap tunneling. This allows us to measure the spectra of bulk (20 nm) and ultrathin (3- and 4-layer) NbSe devices at 70 mK.

Interplay between Magnetism, Superconductivity, and Orbital Order in 5-Pocket Model for Iron-Based Superconductors: Parquet Renormalization Group Study.

We report the results of the parquet renormalization group (RG) analysis of the phase diagram of the most general 5-pocket model for Fe-based superconductors. We use as an input the orbital structure of excitations near the five pockets made out of d_{xz}, d_{yz}, and d_{xy} orbitals and argue that there are 40 different interactions between low-energy fermions in the orbital basis. All interactions flow under the RG, as one progressively integrates out fermions with higher energies.

Emergence of domains and nonlinear transport in the zero-resistance state.

We study transport in the domain state, the so-called zero-resistance state, that emerges in a two-dimensional electron system in which the combined action of microwave radiation and magnetic field produces a negative absolute conductivity. We show that the voltage-biased system has a rich phase diagram in the system size and voltage plane, with second- and first-order transitions between the domain and homogeneous states for small and large voltages, respectively. We find the residual negative dissipative resistance in the stable domain state.

Enhancement of the London penetration depth in pnictides at the onset of spin-density-wave order under superconducting dome.

Recent measurements of the doping dependence of the London penetration depth λ(x) at low T in clean samples of isovalent BaFe2(As(1-x)P(x))2 at T≪T(c) [Hashimoto et al., Science 336, 1554 (2012)] revealed a peak in λ(x) near optimal doping x=0.3.

Quantum-fluctuation effects in the transport properties of ultrathin films of disordered superconductors above the paramagnetic limit.

We study the transport in ultrathin disordered film near the quantum critical point induced by the Zeeman field. We calculate corrections to the normal state conductivity due to quantum pairing fluctuations. The fluctuation-induced transport is mediated by virtual rather than real quasiparticle excitations.

Interpocket pairing and gap symmetry in Fe-based superconductors with only electron pockets.

We analyze the pairing symmetry in Fe-based superconductors AFe2Se2 (A=K, Rb, Cs) which contain only electron pockets. We argue that the pairing condensate in such systems contains not only intrapocket component but also interpocket component, made of fermions belonging to different electron pockets. We analyze the interplay between intrapocket and interpocket pairing, depending on the ellipticity of electron pockets and the strength of their hybridization.

Metal to insulator transition on the N=0 Landau level in graphene.

The magnetotransport in single layer graphene has been experimentally investigated in magnetic fields up to 18 T as a function of temperature. A pronounced T dependence is observed for T≲50  K, which is either metallic, or insulating, depending on the filling factor ν. The metal-insulator transition (MIT) occurs at |ν{c}|∼0.

Nonlinear magnetoresistance oscillations in intensely irradiated two-dimensional electron systems induced by multiphoton processes.

We report on magneto-oscillations in differential resistivity of a two-dimensional electron system subject to intense microwave radiation. The period of these oscillations is determined not only by microwave frequency but also by its intensity. A theoretical model based on quantum kinetics at high microwave power captures all important characteristics of this phenomenon which is strongly nonlinear in microwave intensity.

Dynamics of excitations in a one-dimensional bose liquid.

We show that the dynamic structure factor of a one-dimensional Bose liquid has a power-law singularity defining the main mode of collective excitations. Using the Lieb-Liniger model, we evaluate the corresponding exponent as a function of the wave vector and the interaction strength.

Dynamic response of one-dimensional interacting fermions.

We evaluate the dynamic structure factor S(q, omega) of interacting one-dimensional spinless fermions with a nonlinear dispersion relation. The combined effect of the nonlinear dispersion and of the interactions leads to new universal features of S(q, omega). The sharp peak S(q, omega) approximately q(delta(omega -uq), characteristic for the Tomonaga-Luttinger model, broadens up; for a fixed becomes finite at arbitrarily large .

Spin polarization of electrons by nonmagnetic heterostructures: the basics of spin optics.

We propose to use the lateral interface between two regions with different strengths of the spin-orbit interaction(s) to spin polarize the electrons in gated two-dimensional semiconductor heterostructures. For a beam with a nonzero angle of incidence, the transmitted electrons will split into two spin polarization components propagating at different angles. We analyze the refraction at such an interface and outline the basic schemes for filtration and control of the electron spin.

Relaxation to the invariant density for the kicked rotor.

The relaxation rates to the invariant density in the chaotic phase space component of the kicked rotor (standard map) are calculated analytically for a large stochasticity parameter K. These rates are the logarithms of the poles of the matrix elements of the resolvent, Rinsertion mark(z)=(z-Uinsertion mark)(-1), of the classical evolution operator Uinsertion mark. The resolvent poles are located inside the unit circle.

Relaxation and diffusion for the kicked rotor.

The dynamics of the kicked rotor, which is a paradigm for a mixed system, where the motion in some parts of phase space is chaotic and in other parts is regular, is studied statistically. The evolution operator of phase space densities in the chaotic component is calculated in the presence of noise, and the limit of vanishing noise is taken in the end. The relaxation rates to the equilibrium density are calculated analytically within an approximation that improves with increasing stochasticity.

[Prognostic significance of lactate concentration and indicators of acid-base balance in air embolism of cerebral vessels].

Acid-base balance and lactate concentration in the arterial blood and spinal liquor have been studied in 32 patients after air embolism of the brain vessels developed during cardiopulmonary bypass surgery. It has been shown that an increase of lactate concentration in the spinal liquor over 3.5 mmol/l after air embolism of the brain vessels is indicative of severe hypoxic brain damage, in which the prospect of stable consciousness recovery is doubtful.

[Practical aspects of cardioplegia].

Concentrations of the ingredients have been analysed in a nonstandard cardioplegia solution (CS) and CS from St. Thomas Hospital at the outset before CS introduction into the coronary vessels of patients under cardioplegia. It has been shown that the use of nonstandard CS was accompanied by undesirable variability in ingredient concentration, which to some extent may be accounted for by the use of incompletely unfrozen CS.

[New parameters of the oxygen transport function of arterial blood].

New criteria of the arterial blood oxygen transport function suggested by O. Siggaard-Andersen et al. are reviewed.

[The Soviet colloid modegel as a component of a perfusion medium used in surgery with extracorporeal circulation].

The results of the application of a new Soviet colloid solution modegel in cardiopulmonary bypass surgery in 50 patients have been analysed. The data obtained have been compared to those of control patients who were administered gelatinol instead of modegel. Modegel ensures optimal basic plasma electrolyte content, colloid-osmotic pressure and osmolality during perfusion.

[Regulation of blood oxygen transport function in patients after open-heart surgery].

The oxygen transport function of the blood was studied in 223 patients in the early postoperative period after open-heart surgery, which included correction of acquired cardiac valve defects and aortocoronary bypass. The studied parameters comprised central hemodynamics, pulmonary gas exchange, oxygen supply and utilization, acid-base status, blood gas and lactate content, as well as erythrocytic 2,3-diphosphoglycerate (DPG); Boehringer Mannheim reagents (FRG) were used. The venous blood P50 was calculated using a Severinghaus device.

[Transcutaneous measurement of gas exchange parameters in anesthesiologic practice].

pO2 and pCO2 were studied transcutaneously (tcpO2 and tcpCO2) in 36 patients during reconstructive surgery performed under various multicomponent balanced anesthesia techniques. The results, in the absence of hemodynamic disturbances, serve as a reliable indication of changes in arterial blood pO2 and pCO2 (PaO2 and PaCO2), however, it is impossible to identify transcutaneous PaO2 and PaCO2 values. A decrease in tcpO2 and an increase in tcpCO2 during their dynamic study may give evidence of the inadequacy of controlled lung ventilation.

[Activated coagulation time and the concentration of heparin in assessing the level of blood heparinization during operations using artificial blood circulation].

Blood heparinization was assessed, using two techniques (activated coagulation time--ACT and heparin concentration) in 31 patients during cardiopulmonary bypass surgery. It has been shown that ACT-technique, not always revealing heparin concentration, may serve as a criterion for blood heparinization adequacy during cardiopulmonary bypass, as in every case it reflects individual changes in anticoagulant blood activity.