We consider supersymmetric surface defects in compactifications of
the 6d6d
minimal (D_{N+3},D_{N+3})(DN+3,DN+3)
conformal matter theories on a punctured Riemann surface. For the case
of N=1N=1
such defects are introduced into the supersymmetric index computations
by an action of the BC_1\,(\sim A_1\sim C_1)BC1(∼A1∼C1)
van Diejen model. We (re)derive this fact using three different field
theoretic descriptions of the four dimensional models. The three field
theoretic descriptions are naturally associated with algebras
A_{N=1}AN=1,
C_{N=1}CN=1,
and (A_1)^{N=1}(A1)N=1.
The indices of these 4d4d
theories give rise to three different Kernel functions for the
BC_1BC1
van Diejen model. We then consider the generalizations with
N>1N>1.
The operators introducing defects into the index computations are
certain A_{N}AN,
C_NCN,
and (A_1)^{N}(A1)N
generalizations of the van Diejen model. The three different
generalizations are directly related to three different effective gauge
theory descriptions one can obtain by compactifying the minimal
(D_{N+3},D_{N+3})(DN+3,DN+3)
conformal matter theories on a circle to five dimensions. We explicitly
compute the operators for the A_NAN
case, and derive various properties these operators have to satisfy as a
consequence of 4d4d
dualities following from the geometric setup. In some cases we are able
to verify these properties which in turn serve as checks of said
dualities. As a by-product of our constructions we also discuss a simple
Lagrangian description of a theory corresponding to compactification on
a sphere with three maximal punctures of the minimal
(D_5,D_5)(D5,D5)
conformal matter and as consequence give explicit Lagrangian
constructions of compactifications of this 6d SCFT on arbitrary Riemann
surfaces.