The chemical potential (μ) dependence of the topological susceptibility with two-color two-flavor QCD is studied. We find that at temperature T≈Tc/2, where Tc denotes the critical temperature at zero chemical potential, the topological susceptibility is almost constant throughout 0≤aμ≲1.0, while at T≈Tc, it decreases significantly from the μ=0 value in a high μ regime. In this work, we perform the simulation for μ/T≤16, which covers even the low temperature and the high chemical potential regime. In this regime, we in troduce a diquark source term, which is characterized by j, into the action. We also show our results for the phase diagram in a low temperature regime (T≈Tc/2), which is obtained after taking the j→0 limit of the diquark condensate and the Polyakov loop.
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