Designer Ge quantum dots Coulomb blockade thermometry

A Coulomb blockade (CB) thermometer has been experimentally demonstrated based on the temperature dependence of a Ge quantum-dot (QD) single-hole transistor (SHT). The Ge-QD SHT features distinctive current peaks/plateaus, sharp differential conductance (G_D) dips up to temperature 120K. The full-width-at-half minimum, V_1/2, of the G_D dips directly scale with temperature following the material parameter-independent equation of eV_1/2 ~ 5.44k_BT, providing the primary thermometric quantity. Also the depths of the G_D dips increases with 1/k_BT as expected from CB theory of ΔG_D/G_D0 = E_C/6k_BT. This experimental demonstration indicates that our Ge-QD SHT offers an effective building block for ultrasensitive CB primary thermometers with the detection temperature as high as 115K.