Hi 张金龙, Thanks for posting to the mailing list.

 Recently, I want to calculate the conductance of Superconductor junction.

Let me take the p+ip topological superconductor as the example. Its Hamiltonian is like with \sigma, \tau is the Pauli matrix for spin and particle-hole.

It have particle-hole symmetry:  to g <http://www.baidu.com/link?url=CWxyHp8wHC7mUh2O8wf-aytHhEs_rlRsVxh0fzoMQxTDVixB1fxTsjtNOfSY1CDp9ZBM2c7Xqe5q-YxJQEquWYxqZEF3hL7Sjm9pEpQd58G>uarantee  . ************************** My question is how to write down the K (complex conjugate) operator?

I am not sure what you mean by "write down". You cannot write it down as a matrix; it's defined by its action on wavefunctions. I'm not even sure that I understand your question. What are you actually trying to do? Perhaps reading the tutorial on superconductivity will help: https://kwant-project.org/doc/1/tutorial/superconductors. The example in that tutorial shows how to tell a Builder that your system has particle-hole symmetry. Happy Kwanting, Joe