Back to search## FRINATEK-Fri prosj.st. mat.,naturv.,tek

# Spin-and charge flow in hybrid structures of unconventional superconductors and other novel materials

#### Awarded: NOK 5.7 mill.

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Project Manager:

Project Number:

205591

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Project Period:

2011 - 2016

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Iryna Kulagina has published one paper in Physical Review B, demonstrating a number of quantum effects arising in systems that combine magnetic and superconducting materials. In particular, she has investigated the possibility to utilize supercurrents of spin in order to manipulate magnetic moments, which could find use in cryogenic spintronics. She has demonstrated that a central concept in spintronics known as magnetization switching has a superconducting analog and that it may be controlled via a minute external magnetic field. Moreover, she has managed to solve a complicated analytical problem and derived an expression for the supercurrent in such a system which shows highly anomalous behavior, including a finite flow of spin and charge even at zero phase difference. Kulagina has also submitted a manuscript to Physical Review showing how domain wall motion is manifested in multiferroic system. She has demonstrated how this motion can be controlled via a gate voltage and even induced via spin waves. Finally, she has published a third manuscript in the prestigious journal Nature Scientific Reports where she demonstrates that it is possible to create a spin current flowing without dissipation using only one single homogeneous ferromagnet. This is a groundbreaking result because it has been widely believed that magnetic inhomogeneities are a necessary requirement for generation of such currents.
Peder Galteland has studied phase-transitions in multi-component Bose-Einstein condensates with and without rotation. The focus has been on the effect of varying the strength of many-body interactions in the problem and how they determine the ground states of the system, as well as the competition between many-body ground states and spin.orbit interactions. The latter have the sailent feature of producing non-uniform ground states. The usefulness of studying such phenomena in such Bose-Einstein condensate, is that it allows for a realization of multi-component superfluids under extreme conditions, beyond what can be studied in ordinary condensed matter system known today. Our main findings are that a) strong inter-component many-body interactions leads to immiscibility and phase-separation of non-rotating BECs, b) stripes form in the vortex matter of these systems under rotation as a result of strong many-body interactions, leading to novel types of melting transitions in the condensates, and c) the effects of spin-orbit interactions are suppressed by many-body intercomponent interactions. We expect these results to have some ramifications also for fermionic systems, and thus for applications of for instance spin-orbit coupled strongly correlated systems in spintronics.

Applications related to the synthesis of electricity and magnetism are currently being actively pursued at the nanometer scale. The topics included in this research proposal mainly revolve around quantum mechanical effects related to transport of charge a nd spin of electrons, which is the source for most forms of electricity and magnetism. The study of charge- and spin-transport in systems
where multiple symmetries are broken also offers an important arena for research in terms of fundamental physics. We shall calculate fundamental properties of hybrid structures comprised of materials where magnetism, spin-orbit coupling, and/or superconductivity are present, with the objective to reveal possible
ways of controlling charge- and spin-currents in a well-de fined manner by external control parameters. This will be done both in the context of graphene, iron-pnictide superconductors, topological insulators, superconductor - ferromagnet structures, as well as transition metal ferromagnets. We shall also conside r magnetization dynamics for non-trivial magnetic textures in traditional ferromagnets as well as in graphene. The overarching theme in the project proposal is to illuminate the subtle
interplay between different types of emergent or broken symmetries whe n they appear simultaneously in condensed matter systems.

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3.1BILL. NOKtotal funding in the programme period586PROJECTShave received funding in the programme period3SOURCEShave financed the programme