Tunable temperature induced magnetization jump in a GdVO3 single crystal

We report a novel feature of the temperature induced magnetization jump observed along the a-axis of the GdVO3 single crystal at temperature TM = 0.8 K. Below TM, the compound shows no coercivity and remanent magnetization indicating a homogenous antiferromagnetic structure. However, we will demonstrate that the magnetic state below TM is indeed history dependent and it shows up in different jumps in the magnetization only when warming the sample through TM. Such a magnetic memory effect is highly unusual and suggesting different domain arrangements in the supposedly homogenous antiferromagnetic phase of the compound.Comment: 17 pages, 8 Figure

Frustration phenomena in Josephson point contacts between single-band and three-band superconductors

Within the formalism of Usadel equations the Josephson effect in dirty point contacts between single-band and three-band superconductors is investigated. The general expression for the Josephson current, which is valid for arbitrary temperatures, is obtained. We calculate current-phase relations for very low temperature and in the vicinity of the critical temperature. For three-band superconductors with broken time-reversal symmetry (BTRS) point contacts undergo frustration phenomena with different current-phase relations, corresponding to {\phi}-contacts. For three-band superconductors without BTRS we have close to sinusoidal current-phase relations and absence of the frustration, excepting the case of very low temperature, where under certain conditions two ground states of the point contact are realized. Our results can be used as the potential probe for the detection of the possible BTRS state in three-band superconducting systems.Comment: 14 pages, 7 figure

Nanometer scale electronic reconstruction at the interface between LaVO3 and LaVO4

Electrons at interfaces, driven to minimize their free energy, are distributed differently than in bulk. This can be dramatic at interfaces involving heterovalent compounds. Here we profile an abrupt interface between V 3d2 LaVO3 and V 3d0 LaVO4 using electron energy loss spectroscopy. Although no bulk phase of LaVOx with a V 3d1 configuration exists, we find a nanometer-wide region of V 3d1 at the LaVO3/LaVO4 interface, rather than a mixture of V 3d0 and V 3d2. The two-dimensional sheet of 3d1 electrons is a prototypical electronic reconstruction at an interface between competing ground states.Comment: 14 pages, 5 figure

Fermi point in graphene as a monopole in momentum space

We consider the effective field theory of graphene monolayer with the Coulomb interaction between fermions taken into account. The gauge field in momentum space is introduced. The position of the Fermi point coincides with the position of the corresponding monopole. The procedure of extracting such monopoles during lattice simulations is suggested.Comment: Latex, 12 page

Magnetic Order and Dynamics in an Orbitally Degenerate Ferromagnetic Insulator

Neutron scattering was used to determine the spin structure and the magnon spectrum of the Mott--Hubbard insulator YTiO$_3$. The magnetic structure is complex, comprising substantial G-type and A-type antiferromagnetic components in addition to the predominant ferromagnetic component. The magnon spectrum, on the other hand, is gapless and nearly isotropic. We show that these findings are inconsistent with the orbitally ordered states thus far proposed for YTiO$_3$ and discuss general implications for a theoretical description of exchange interactions in orbitally degenerate systems.Comment: to appear in Phys. Rev. Let

Structural, electronic, and magneto-optical properties of YVO3_3

Optical and magneto-optical properties of YVO$_3$ single crystal were studied in FIR, visible, and UV regions. Two structural phase transitions at 75 K and 200 K were observed and established to be of the first and second order, respectively. The lattice has an orthorhombic $Pbnm$ symmetry both above 200 K as well as below 75 K, and is found to be dimerized monoclinic $Pb11$ in between. We identify YVO$_3$ as a Mott-Hubbard insulator with the optical gap of 1.6 eV. The electronic excitations in the visible spectrum are determined by three $d$-bands at 1.8, 2.4, and 3.3 eV, followed by the charge-transfer transitions at about 4 eV. The observed structure is in good agreement with LSDA+$U$ band structure calculations. By using ligand field considerations, we assigned these bands to the transitions to the $^4A_{2g}$, $^2E_{g} + ^2T_{1g}$, and $^2T_{2g}$ states. The strong temperature dependence of these bands is in agreement with the formation of orbital order. Despite the small net magnetic moment of 0.01 $\mu_B$ per vanadium, the Kerr effect of the order of $0.01^\circ$ was observed for all three $d$-bands in the magnetically ordered phase $T_{\text{N\'eel}}<116 K$. A surprisingly strong enhancement of the Kerr effect was found below 75 K, reaching a maximum of $0.1^\circ$. The effect is ascribed to the non-vanishing net orbital magnetic moment.Comment: Submitted to Phys. Rev.

Neutron diffraction study of YVO3, NdVO3, and TbVO3

The structural and magnetic properties of YVO3, NdVO3 and TbVO3 were investigated by single-crystal and powder neutron diffraction. YVO3 shows a structural phase transition at 200 K from an orthorhombic structure with the space group Pbnm to a monoclinic one with the space group P21/b. But supplementary high-resolution synchrotron diffraction experiments showed that the monoclinic distortion is extremely small. A group theoretical analysis shows that this magnetic state in the monoclinic phase is incompatible with the lattice structure, unless terms of higher than bilinear order in the spin operators are incorporated in the spin Hamiltonian. This observation is discussed in the light of recent theories invoking unusual many-body correlations between the vanadium t2g orbitals. A structural phase transition back to the orthorhombic space group Pbnm is observed upon cooling below 77 K. This transition is accompanied by a rearrangement of the magnetic structure into a mode compatible with the lattice structure. The crystal structures of NdVO3 and TbVO3 are closely similar to that of YVO3. However, only a single magnetic phase transition was found in the vanadium sublattice down to 9.5 K. Below 60 K the magnetic moments of the Nd- and Tb-ions are gradually polarized by the ordered vanadium moments. Below 11 K, we found a noncollinear order of the terbium moments

The Nambu sum rule and the relation between the masses of composite Higgs bosons

We review the known results on the bosonic spectrum in various NJL models both in the condensed matter physics and in relativistic quantum field theory including $^3$He-B, $^3$He-A, the thin films of superfluid He-3, and QCD (Hadronic phase and the Color Flavor Locking phase). Next, we calculate bosonic spectrum in the relativistic model of top quark condensation suggested in \cite{Miransky}. In all considered cases the sum rule appears that relates the masses (energy gaps) $M_{boson}$ of the bosonic excitations in each channel with the mass (energy gap) of the condensed fermion $M_f$ as $\sum M_{boson}^2 = 4 M_f^2$. Previously this relation was established by Nambu in \cite{Nambu} for $^3$He-B and for the s - wave superconductor. We generalize this relation to the wider class of models and call it the Nambu sum rule. We discuss the possibility to apply this sum rule to various models of top quark condensation. In some cases this rule allows to calculate the masses of extra Higgs bosons that are the Nambu partners of the 125 GeV Higgs.Comment: Latex, 15 page

On the non-Abelian Stokes theorem for SU(2) gauge fields

We derive a version of non-Abelian Stokes theorem for SU(2) gauge fields in which neither additional integration nor surface ordering are required. The path ordering is eliminated by introducing the instantaneous color orientation of the flux. We also derive the non-Abelian Stokes theorem on the lattice and discuss various terms contributing to the trace of the Wilson loop.Comment: Latex2e, 0+14 pages, 3 figure

Organisational and methodological challenges of CAR-T manufacturing in the Russian Federation

Despite their widespread clinical implementation, chimeric antigen receptor T-cell (CAR-T) therapy products, including those manufactured by industrial processes, are still not legally available or used in the Russian Federation.The aim of the study was to describe the current challenges associated with specific aspects of CAR-T manufacturing in the Russian Federation and the potential ways to overcome them.This article discusses the regulatory, legal, organisational, and methodological challenges of CAR-T manufacturing. It analyses differences in the interpretation of CAR-T therapy products under national and supranational law. According to Russian Federal Law No. 180-FZ “On Biomedical Cell Products” of 23 June 2016, CAR-T therapy products are considered biomedical cell products. However, according to Decision No. 78 of the Council of the Eurasian Economic Commission “On the Rules of Marketing Authorisation and Assessment of Medicinal Products for Human Use” of 3 November 2016, CAR-T therapy products are considered advanced therapy medicinal products (ATMPs). This article provides a detailed overview of the difficulties in obtaining starting biological materials (i.e. the inability to consider the patient as a donor) and transferring the materials for CAR-T manufacturing (i.e. the inapplicability of national law). In addition, this article describes export aspects specific to biological materials. The authors reckon that CAR-T therapy products should be categorised as ATMPs and that the corresponding active pharmaceutical ingredients, genetically modified autologous lymphocytes, should be defined as starting materials. Therefore, genetically modified autologous lymphocytes should be regulated under the requirements for starting materials for the manufacturing of active pharmaceutical ingredients that are set forth in Decision No. 77 of the Council of the Eurasian Economic Commission “On the Adoption of the Rules of Good Manufacturing Practice of the Eurasian Economic Union” of 3 November 2016. In conclusion, the authors recognise the need for national and supranational law harmonisation. For this task, it is necessary to establish expert groups that will include clinicians, legal experts, and representatives from the relevant authorities and the pharmaceutical industry