[LA-SiGMA] LASiGMA Seminar - Dr. Mario Cuoco, 3:30pm at Louisiana State University

[shelley lee]

Dear All,

 

Dr. Mario Cuoco of the University of Salerno will be giving a seminar
Wednesday, October 23rd,  at 3:30 pm in 1008B in the Digital Media Center at
the Louisiana State University. The title of his talk is "Spin-triplet
superconductors: interface to itinerant ferromagnets and magnetic edge
states "

 

Abstract:

This talk will introduce the physical properties of spin-triplet
superconductors [1] which will focus on two remarkable effects: i) the
spin-orbital coupling emerging at the interface with an itinerant
ferromagnet (FM) [2], ii) the occurrence of magnetic Andreev states at their
edge if the system allows for singlet pairing in a subdominant channel [3].
In a TSC-FM hetero-structure, the orientation of the FM moment relative to
the TSC vector order parameter is a crucial variable that controls the
physical behavior. In addition to the pair breaking, spin-flip reflection
processes at the interface with the FM scatter the triplet Cooper pairs
between the spin up and down condensates, setting up an effective
Josephson-like coupling between them. [4] The pair-breaking and spin
Josephson coupling both make significant contributions to the free energy of
a TSC-FM junction through the proximity effect, interface electronic
reconstruction, and the variation of the TSC gap. Although these
contributions depend upon the direction of the FM's exchange field, the two
effects do not necessarily act constructively. For a single-component p-wave
TSC, we find that the variation of the gap controls the orientation of the
FM's moment via the change in condensation energy. The stable configuration
is either parallel or perpendicular to the TSC vector order parameter,
depending on the alignment of the TSC gap with respect to the interface,
thus evidencing a unique form of spin-orbital coupling. The competing
orbital components of the chiral px+ipy state generate a non-unique behavior
and a first-order transition from the perpendicular to the parallel
configuration as the FM exchange field is increased. When the interface is
imperfect or spin active the scenario is different and other processes can
play the decisive role in setting the magnetic profile [5]. Concerning the
surface states of TSC, novel magnetic effects can occur if triplet and
singlet pairing get mixed and have a non-uniform spatial profile. The talk
will also show that a) a subdominant in-phase s-wave superconducting order
can exist near the edge of the sample; b) the in-phase s-wave component
gives a non-unitary superconducting state at the boundary; c) as a result,
the bound states are spin-polarized, leading to a finite surface
magnetization; d) spin current flows along the interface in this regime; e)
surface charge currents exhibit anomalous dependence on the magnetization
[3].

 

Biography:

Mario Cuoco has been a CNR researcher since 2002 and currently at the
CNR-SPIN Institute ("Superconductors, oxides and other Innovative materials
and devices") in Salerno (Italy). His research activity deals with the
investigation of systems with competing superconductivity and magnetism;
modelling and computation of electronic, magnetic and transport properties
of correlated systems, mainly oxides in bulk and hetero-structures.
(Co-)author of about 90 articles on peer review international journals. He
has contributed to research activities on transition metal oxides and
hetero-structures at large scale facilities: muon-spin spectroscopy, X-ray
absorption, angle resolved photoemission and neutron analyses. He has been
the scientific coordinator of the Regional Project about "Superconducting
states in metallic ferromagnets: mechanisms and patterns of mixed phases".
Awarded as Marie-Curie Research Fellow within the European program
"Improving Human Potential". He is the coordinator of the European FP7
RegPot project "MAMA (Multifunctional Advanced Materials and Nanoscale
Phenomena)" funded by the EC.

 

Please note, due to technical difficulties this seminar will ONLY be
available via abobe connect. Please click on the link provided:
<http://connect.lsu.edu/la-sigma/> http://connect.lsu.edu/la-sigma/

 

UNO - Liberal Arts Building 234

LATech - PML 1015, Center for Instructional Technology, at the Wyly Tower

 

Please see attached flyer and let me know if you have any questions.

 

Regards,

Shelley Lee

Project Coordinator

225-578-0465

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