Quantum enhanced Josephson junction field-effect transistors for logic applications

•A new device structure of quantum enhanced JJFETs was proposed and demonstrated.•New JJFETs utilize sharp quantum phase transition of an excitonic insulator state.•New JJFETs are promising for low-energy, power-efficient microelectronics. Josephson junction field-effect transistors (JJFETs) have recently re-emerged as promising candidates for superconducting computing. For JJFETs to perform Boolean logic operations, the so-called gain factor αR must be larger than 1. In a conventional JJFET made with a classical channel material, due to a gradual dependence of superconducting critical current on the gate bias, αR is much smaller than 1. In this Letter, we propose a new device structure of quantum enhanced JJFETs in a zero-energy-gap InAs/GaSb heterostructure. We demonstrate that, due to an excitonic insulator quantum phase transition in this zero-gap heterostructure, the superconducting critical current displays a sharp transition as a function of gate bias, and the deduced gain factor αR ∼ 0.06 is more than 50 times that (∼0.001) reported in a classical JJFET. Further optimization may allow achieving a gain factor larger than 1 for logic applications.