Superconductivity and magnetism in Cu2+-based coordination polymer [Cu3C6S6]n

Cu-BHT exhibits perfect kagome lattice of Cu2+ and previous combined magnetization and specific heat results suggested the presence of strong spin fluctuations. If there are indeed spin fluctuations arising from the frustrated Cu2+ kagome lattice where superconductivity occurs below 0.25 K, one would expect that spin fluctuations may play an important role in driving the superconductivity. However, our previous neutron scattering measurements on 9 grams of Cu-BHT powder did not observe magnetic excitations in the energy range above 0.2meV at 300mK. Therefore, it is still unclear whether magnetic order (and fluctuations at lower energy) is absent below 2K and the superconducting pairing is associated with spin fluctuations. To resolve this issue, we proposed to explore the superconducting gap symmetry and magnetic order of Cu-BHT at low temperature 40mK-3K.