0000000001203628
AUTHOR
P. Virtanen
Nonlinear σ model for disordered systems with intrinsic spin-orbit coupling
We derive the nonlinear σ model to describe diffusive transport in normal metals and superconductors with intrinsic spin-orbit coupling (SOC). The SOC is described via an SU(2) gauge field, and we expand the model to the fourth order in gradients to find the leading non-Abelian field-strength contribution. This contribution generates the spin-charge coupling that is responsible for the spin-Hall effect. We discuss how its symmetry differs from the leading quasiclassical higher-order gradient terms. We also derive the corresponding Usadel equation describing the diffusive spin-charge dynamics in superconducting systems. As an example, we apply the obtained equations to describe the anomalous…
Phase-dependent microwave response of a graphene Josephson junction
Gate-tunable Josephson junctions embedded in a microwave environment provide a promising platform to in situ engineer and optimize novel superconducting quantum circuits. The key quantity for the circuit design is the phase-dependent complex admittance of the junction, which can be probed by sensing a radio frequency SQUID with a tank circuit. Here, we investigate a graphene-based Josephson junction as a prototype gate-tunable element enclosed in a SQUID loop that is inductively coupled to a superconducting resonator operating at 3 GHz. With a concise circuit model that describes the dispersive and dissipative response of the coupled system, we extract the phase-dependent junction admittanc…
Giant enhancement to spin battery effect in superconductor/ferromagnetic insulator systems
We develop a theory of the spin battery effect in superconductor/ferromagnetic insulator (SC/FI) systems taking into account the magnetic proximity effect. We demonstrate that the spin-energy mixing enabled by the superconductivity leads to the enhancement of spin accumulation by several orders of magnitude relative to the normal state. This finding can explain the recently observed giant inverse spin Hall effect generated by thermal magnons in the SC/FI system. We suggest a nonlocal electrical detection scheme which can directly probe the spin accumulation driven by the magnetization dynamics. We predict a giant Seebeck effect converting the magnon temperature bias into the nonlocal voltag…
Coupling the Higgs mode and ferromagnetic resonance in spin-split superconductors with Rashba spin-orbit coupling
We show that the Higgs mode of superconductors can couple with spin dynamics in the presence of a static spin-splitting field and Rashba spin-orbit coupling. The Higgs-spin coupling dramatically modifies the spin susceptibility near the superconducting critical temperature and consequently enhances the spin pumping effect in a ferromagnetic insulator/superconductor bilayer system. We show that this effect can be detected by measuring the magnon transmission rate and the magnon-induced voltage generated by the inverse spin Hall effect.
Regulation of synthesis of fibrillar collagens in rat skeletal muscle during immobilization in shortened and lengthened positions
Immobilization has been shown to cause muscle atrophy and decreased total collagen synthesis in skeletal muscle. These changes can be counteracted by stretch. The purpose of this study was to find out the early effects of immobilization in shortened and lengthened positions on expression of type I and III collagen at pre- and post-translational level. The mRNA levels of type I and III collagen, prolyl 4-hydroxylase activity, total collagen concentration and the proportions of type I and III collagens were analysed in soleus (SOL), gastrocnemius (GM), extensor digitorum longus and tibialis anterior (TA) muscles during immobilization in shortened and lengthened positions for 1, 3 and 7 days. …
Magnetoelectric effects in superconductors due to spin-orbit scattering : Nonlinear σ-model description
We suggest a generalization of the nonlinear σ model for diffusive superconducting systems to account for magnetoelectric effects due to spin-orbit scattering. In the leading orders of spin-orbit strength and gradient expansion, it includes two additional terms responsible for the spin-Hall effect and the spin-current swapping. First, assuming a delta-correlated disorder, we derive the terms from the Keldysh path integral representation of the generating functional. Then we argue phenomenologically that they exhaust all invariants allowed in the effective action to the leading order in the spin-orbit coupling (SOC). Finally, the results are confirmed by a direct derivation of the saddle-poi…
Synthesis and degradation of type IV collagen in rat skeletal muscle during immobilization in shortened and lengthened positions
Aim: Type IV collagen is a major protein in basement membranes surrounding and supporting skeletal muscle cells. In the present study, we tested the hypotheses that immobilization down-regulates synthesis and up-regulates degradation of type IV collagen in skeletal muscle. Methods: mRNA level and concentration of type IV collagen as well as mRNA levels and activities of proteins involved in its degradation were analysed from soleus (SOL), gastrocnemius (GAS) and extensor digitorum longus muscles after immobilization in shortened and lengthened positions for 1, 3 and 7 days. Results: Following immobilization, type IV collagen mRNA level was decreased in SOL and GAS suggesting down-regulat…
Directly probing the chirality of Majorana edge states
We propose to directly probe the chirality of Majorana edge states in 2D topological superconductors using polarization selective photon absorption. When shining circularly polarized light on a 2D topological superconductor in disk geometry, the photons can excite quasiparticles only when the polarization of the light matches the chirality of the Majorana edge states required by the angular momentum conservation. Hence, one can obtain the chirality of the Majorana edge states by measuring the photon absorption rate. We show that the polarization selective photon absorption can also serve as smoking gun evidence of the chiral Majorana edge mode.
Superconductivity provides a giant enhancement to the spin battery effect
We develop a theory of the spin battery effect in superconductor/ferromagnetic insulator (SC/FI) systems taking into account the magnetic proximity effect. We demonstrate that the spin-energy mixing enabled by the superconductivity leads to the enhancement of spin accumulation by several orders of magnitude relative to the normal state. This finding can explain the recently observed giant inverse spin Hall effect generated by thermal magnons in the SC/FI system. We suggest a non-local electrical detection scheme which can directly probe the spin accumulation driven by the magnetization dynamics. We predict a giant Seebeck effect converting the magnon temperature bias into the non-local volt…
Biochemical composition of muscle extracellular matrix: the effect of loading
Collagen plays an important role in skeletal muscle both during muscle differentiation and normal muscle growth, and also serves a role as a supportive structure. It is the most abundant protein of the extracellular matrix and of the 19 distinct collagen types, types I, III, IV and V are the dominating ones in skeletal muscle. Both collagen synthesis as well as degradation is influenced by either physical loading or immobilization in skeletal muscle, and recent methods have allowed for greater understanding of the posttranslational processing of collagen.