In this paper, a quantum gas obeying Gentile statistics is investigated in a rotating harmonic trap. The single-particle energy spectrum is obtained by solving the Schrödinger equation with a rotational term. Based on this spectrum, we calculate the temperature dependence of fugacity and obtain an analytical expression for the first-order correction to the fugacity arising from rotation. The correction is shown to be negative, indicating a downward shift in fugacity. For cases where analytical methods are not applicable, numerical calculations are performed to analyze the temperature dependence of the fugacity.

In 1965, Kohn and Luttinger published a note revealing that dynamical screening of the repulsive Coulomb interaction leads, under certain conditions, to an effective attraction necessary for the formation of Cooper pairs. We propose such a formalism adapted to the cuprates, where the screening arises from the superexchange dynamics of virtual holes in the oxygen orbitals of the CuO2 plane. Using an adequate Schrieffer–Wolff transformation, the basic Hartree–Fock–Bogoliubov method, and the ab initio data on orbitals (energy, hopping, interaction), we derive some predictions for the temperature-doping phase diagram (pseudo-gap, strange metal, antiferromagnetism, superconducting, and normal states) and for the doping-dependent band energy spectrum in semi-quantitative agreement with observations.

Within the framework of the developed theoretical approach, the temperature dependences of the resistivity ρ(T), excess conductivity σ′(T), and pseudogap (PG) Δ*(T) in YBa2Cu3O7–δ and Y1–xPrxBa2Cu3O7–δ (x = 0.05) single crystals under effect of high-energy electron irradiation and hydrostatic pressure up to 1.7 GPa were analyzed. It is shown that the effect of the external factors is rather specific. This specificity can be detected by analyzing the properties of the fluctuation conductivity and PG, which turned out to be much more sensitive to changes in the internal electronic subsystems caused by induced defects than the specific resistance. The unusual behavior of high-temperature superconductor single crystals under the influence of external factors is examined in detail.

Tunneling two-level systems (TLS) were proposed as an ad hoc explanation of the ubiquitous low-frequency (1/f) noise in solid-state devices. Now their existence and, in certain cases, quantum coherent behavior are confirmed by direct observation. The latter allowed the use of TLS within superconducting qubits as quantum memory devices.

Rashba spin-orbit interactions generated by time-dependent electric fields acting on weak links (that couple together non-magnetic macroscopic leads) can magnetize the junction. The Rashba spin-orbit interaction that affects the spins of electrons tunneling through the weak links changes their momentum concomitantly. We establish the connection between the magnetization flux induced by processes that conserve momentum and the magnetization created by tunneling events that do not. Control of the induced magnetization can be achieved by tuning the polarization of the ac electric field responsible for the spin-orbit Rashba interaction (e.g., from being circular to linear), by changing the applied bias voltage, and by varying the degree of a gate voltage-induced asymmetry of the device.

In this paper, we study intraband optical transitions in a Neumann quantum well. Using the energy spectrum and wave function of an electron in such a well, we obtain an analytical expression for the absorption coefficient for intraband optical transitions. Graphs of the absorption coefficient versus photon energy are presented for different quantum well widths and for several types of intraband transitions. Analysis of the graphs demonstrates that an increase in the well width leads to an increase in the maximum absorption coefficient and its shift to higher energies (blue shift) relative to the incident photon energy. The probability of optical transitions to higher energy levels increases. This is due to stronger absorption at these levels compared to lower-energy states. The results obtained are in good agreement with the data presented in other papers on this topic.

Ferromagnetic properties of the perovskite structures, namely, [NH2–CH+–NH2] [Mn(HCOO)3] (FMDMn) and [CH3C(NH2)2] [Mn(HCOO)3] (AceMn), are studied close to magnetic phase transitions. Magnetization M(T) is calculated by the extended mean field model, and M(H) is analyzed for FMDMn near Tc = 8 K. For AceMn, this analysis is performed using M/H(χac′) and M(H) near Tc = 9 K. The observed data from the literature are used for the power-law analysis. The critical exponents β, δ, and γ for M(T), M/H, and M(H), respectively, are determined, which are compared with the expected values from the mean field theory, Ising and Heisenberg models. We find that the Landau mean-field model satisfactorily describes the magnetic behavior of M(T) values for the perovskite FMDMn. Our γ and δ values are not in agreement with those expected ones. It is indicated that both compounds (FMDMn and AceMn) exhibit weak first-order (or nearly second-order) behavior; in particular, a tricritical magnetic transition is suggested for FMDMn.

Optical lattices are essential tools in the field of ultra-cold atomic physics. In this study, we theoretically demonstrate that sub-wavelength confinement can be achieved in these lattices through superoscillations. This generic wave phenomenon occurs when a local region of the wave oscillates faster than any of the frequencies in its global Fourier decomposition. To illustrate this, we consider a one-dimensional tri-chromatic optical potential confining a spinless Bose–Einstein condensate of 87Rb atoms. By numerically optimizing the relative phases and amplitudes of the optical trap’s frequency components, it is possible to generate superoscillatory spatial regions. Such regions contain multiple density peaks at sub-wavelength spacing. This work establishes superoscillations as a viable method of confining a Bose–Einstein condensate in a blue-detuned optical lattice at the sub-wavelength scale.