Cryogenic Control of Spin Qubits
2DEG-Based Gate-Tunable Heat Switch for Ultra-Low Temperature Cooling of High-Impedance Devices
3:00 pm – 3:12 pmCooling nanoelectronic devices to temperatures below the base temperature of dilution refrigerators is challenging due to poor electron-phonon coupling at ultra-low temperatures. Furthermore, Wiedemann-Franz cooling becomes ineffective for devices with high impedance, limiting efficient cooling via cold electrons.
We present a gate-tunable heat switch designed to bypass this limitation by creating a secondary, low-resistance cooling path through a high-mobility two-dimensional electron gas (2DEG) with ultra-low ohmic contacts. In this approach, Coulomb blockade thermometer (CBT) islands are coupled to a microkelvin environment through the 2DEG, enabling efficient heat extraction via electron cooling. The gate modulates the 2DEG beneath the CBT: in the cooling phase, the gate is held grounded, keeping the heat switch closed and allowing heat flow, while in the measurement phase, the gate depletes the 2DEG, thermally and electrically isolating the device from the environment. By alternating between cooling and measurement steps, we observe CBT temperatures dropping from 6 mK to well below 2 mK, beyond the measurement range of the thermometer. This technique opens new possibilities for cooling high-impedance nanoelectronics to ultra-low temperatures.