Silver-Epoxy Microwave Filters and Thermalizers for Millikelvin Experiments

Abstract: We present Silver-epoxy filters combining excellent microwave attenuation with efficient wire thermalization, suitable for low temperature quantum transport experiments. Upon minimizing parasitic capacitances, the attenuation reaches >100 dB above ~150 MHz and - when capacitors are added - already above ~30 MHz. We measure the device electron temperature with a GaAs quantum dot and demonstrate excellent filter performance. Upon improving the sample holder and adding a second filtering stage, we obtain electron temperatures as low as 7.5 +/- 0.2 mK in metallic Coulomb blockade thermometers.