The Super Cryogenic Dark Matter Search experiment ( SuperCDMS ) at the Soudan Underground Laboratory studied energy loss associated with defect formation in germanium crystals at mK temperatures using in situ ^ { 210 } Pb sources .
We examine the spectrum of ^ { 206 } Pb nuclear recoils near its expected 103 keV endpoint energy and determine an energy loss of \left ( 6.08 \pm 0.18 \right ) % , which we attribute to defect formation .
From this result and using TRIM simulations , we extract the first experimentally determined average displacement threshold energy of \left ( 19.7 ^ { +0.6 } _ { -0.5 } \right ) eV for germanium .
This has implications for the analysis thresholds of future germanium-based dark matter searches .