From ec7993eff371d803cc1442fafe570702c7d25f3e Mon Sep 17 00:00:00 2001
From: Pablo San-Jose <lekand@gmail.com>
Date: Thu, 28 Nov 2024 08:56:24 +0100
Subject: [PATCH] More general Quantica.gaps

---
 src/observables.jl | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/observables.jl b/src/observables.jl
index c5b472a4..40ccd5bf 100644
--- a/src/observables.jl
+++ b/src/observables.jl
@@ -760,7 +760,7 @@ end
 # gap(::Hamiltonian, µ = 0, ...) -> minimum gap in the bands around µ
 #region
 
-function gaps(h::Hamiltonian{T,<:Any,1}, µ = 0, ϕstore = missing; atol = eps(T)) where {T}
+function gaps(h::Hamiltonian{T,<:Any,1}, µ = 0, ϕstore = missing; atol = eps(T), nev = 1, kw...) where {T}
     g = greenfunction(h, GS.Schur())
     λs = schur_eigvals(g, µ)
     cϕs = λs .= -im .* log.(λs) # saves one allocation
@@ -771,9 +771,11 @@ function gaps(h::Hamiltonian{T,<:Any,1}, µ = 0, ϕstore = missing; atol = eps(T
     rϕs = real.(cϕs)
     iϕs = chopsmall.(abs.(imag.(cϕs)), atol)
     ϕstore === missing || copy!(ϕstore, cϕs)
-    solver = ES.ShiftInvert(ES.ArnoldiMethod(nev = 1), µ)
+    solver = ES.ShiftInvert(ES.ArnoldiMethod(; nev, kw...), µ)
     n = flatsize(h)
-    Δs = [iszero(iϕ) || rank(h(rϕ)-µ*I; tol=atol) < n ? zero(T) : abs(first(energies(spectrum(h, rϕ; solver)))-µ) for (rϕ, iϕ) in zip(rϕs, iϕs)]
+    Δs = [iszero(iϕ) || rank(h(rϕ)-µ*I; tol=atol) < n ?
+        zero(T) :
+        abs(minimum(x->abs(x-µ), energies(spectrum(h, rϕ; solver)))-µ) for (rϕ, iϕ) in zip(rϕs, iϕs)]
     return Δs
 end