Speaker
Prof.
Egor Babaev
Description
In the recent years the interest in multicomponent
superconductivity is growing due to discoveries of
multiband superconducting materials and renewed experimental
pursuit of the projected superconducting states of metallic
hydrogen and deuterium as well as some applications in the
physics of pulsars. In this talk I will overview two topics in
multicomponent superconductivity.
(i) Within the standard paradigm the magnetic properties of
superconductors are dictated by the mass of the gauge field
acquired via the Andersson-Higgs effect. I will discuss
that in multicomponent superconductors the fluctuating gauge
field can alter this physics by generation of
Faddeev-Skyrme-like terms which makes free energy of a
multicomponent superconductors mappable onto a version of
ostensibly unrelated Faddeev-Skyrme model. I will give a
number of examples how this leads to entirely novel
physics in multicomponent theories: non-exponential
localization and nonmonotonoc behavior of magnetic field
inside a superconductor with local electrodynamics,
topological excitations in the form of vortex loops which
energy is a non-monotonic function of the size of the defect
etc. I will argue that it should lead to new physics of
post-quench relaxation, new kind of superfluid turbulence
and other phenomena which have no counterparts in
single-component systems. (partially based on [1])
(ii) In contrast to single-component superconductors, which
are described at the level of Ginzburg-Landau theory by a
single Ginzburg-Landau parameter and are divided in type-I
and type-II classes, two-component systems in general
possesses three fundamental length scales and have been
shown to possess a separate "type-1.5" superconducting state
[2]. In that state, as a consequence of the extra
fundamental length scale, vortices attract one another at
long range but repel at shorter ranges, and therefore should
form clusters in low magnetic fields. In such clusters one
can define a negative interface energy inside a cluster and
at the same there one can define a positive interface energy
associated with the cluster's boundary. In particular I will
discuss that, in some temperature range, the type-1.5
superconductivity can exist in multiband materians even
when there is a substantial interband couplings such as
intrinsic Josephson coupling.
Based on:
[1]
Egor Babaev Phys. Rev. B 79, 104506 (2009)
Egor Babaev, Juha Jäykkä, Martin Speight Phys. Rev. Lett
103, 237002 (2009)
[2]
E. Babaev & J.M. Speight Phys.Rev. B 72 180502 (2005)
Johan Carlstrom, Egor Babaev, Martin Speight arXiv:1009.2196
E. Babaev, J. Carlstrom, J. M. Speight Phys. Rev. Lett. 105,
067003 (2010)
