I am using Schwalbe lugano 700*25C for commuting, it's a almost brand new tyre with less than 500km. Recently I am starting to find some cuts around 1cm on my the tyre thread. Does anyone know what's the cause of a tyre cut? I inflate the tyre slightly above the max rated psi, is that part of the problem?
That looks like broken glass cut to me, you might find the remains of the sliver in the bottom of the cut. Over time that fragment will work inwards and eventually you will get a puncture.
That's left will be smaller than this, the sharp, flat edge that actually cut into your tyre then broke off:
One maintenance task some people do is to get a sharp metal object and dig all the little splinters of glass out of their tyres. That does reduce the number of punctures, but in my experience it saves ten minutes of puncture repair for every hour or two of picking bits out of the tyre. It's not worth it. Instead I use puncture resistant tyres, which are heavier and slower than ones like yours. I probably spend an extra hour riding for every ten minutes of puncture fixing avoided... but I ride partly for fitness so that doesn't bother me.