Researchers have experimentally demonstrated the Josephson diode effect in a simple three-terminal Josephson device based on an InAs two-dimensional electron gas (2DEG) proximitized by an epitaxial aluminum layer.
This diode effect is a consequence of a synthetic realization of a Josephson current-phase relation (CφR) that contains higher harmonic terms with a phase difference provided by an applied magnetic field. The diode can be switched between positive and negative polarity by a small out-of-plane magnetic field or electrostatic gating. This work establishes that the Josephson diode effect can be realized in any material system exhibiting the conventional CφR.
Facts
- 💡 Josephson junctions (JJs) with non-reciprocal critical current can realize a superconducting diode, where the magnitude of the critical current depends on the bias direction.
- 💡 The researchers fabricated three-terminal Josephson devices on InAs 2DEG proximitized by an epitaxial aluminum layer.
- 💡 The three superconducting terminals of the device are labeled 1, 2, and 0, forming a Y-shaped junction.
- 💡 The diode effect is a consequence of the synthetic realization of a Josephson current-phase relation that contains higher harmonic terms with a phase difference provided by an applied magnetic field.
- 💡 The diode can be switched between positive polarity (positive-bias critical current larger than negative-bias critical current) and negative polarity (negative-bias critical current larger than positive-bias critical current) by a small out-of-plane magnetic field or electrostatic gating.
- 💡 The diode effect is independent of the material platform used and can be realized in any material system exhibiting the conventional current-phase relation.
- 💡 The diode efficiency factor can reach up to ~48% in the presented devices, and rectification of supercurrents has been demonstrated.
Researchers have demonstrated the realization of the Josephson diode effect in a three-terminal Josephson device based on an InAs two-dimensional electron gas (2DEG) proximitized by an epitaxial aluminum layer. The diode effect arises from a synthetic realization of a Josephson current-phase relation (CφR) that contains higher harmonic terms with a phase difference provided by an applied magnetic field. The devices consist of a Y-shaped junction with three superconducting terminals. By applying a small out-of-plane magnetic field or electrostatic gating, the diode can be switched between positive polarity (positive-bias critical current larger than negative-bias critical current) and negative polarity (negative-bias critical current larger than positive-bias critical current). The diode effect is not specific to the material system used in this study but can be realized in any material system exhibiting the conventional current-phase relation. The diode efficiency factor, which measures the asymmetry between positive and negative bias, reaches up to ~48% in the presented devices. Furthermore, the researchers demonstrate the rectification of supercurrents in the diode, where the device remains superconducting for one cycle of a square-wave current signal and has a finite voltage drop for the opposite cycle. This work opens up possibilities for the development of dissipationless electronics and gate-tunable building blocks of superconducting circuits.
Gate-tunable superconducting diode effect in a three-terminal Josephson device – nature communications
Mohit Gupta, Gino V. Graziano, Mihir Pendharkar, Jason T. Dong, Connor P. Dempsey, Chris Palmstrøm & Vlad S. Pribiag
FAQ
Q: What is the Josephson diode effect?
A: The Josephson diode effect refers to the phenomenon where a superconducting diode is created using Josephson junctions. In this effect, the magnitude of the critical current flowing through the diode depends on the direction of the bias.
Q: What is a three-terminal Josephson device?
A: A three-terminal Josephson device is a device that consists of three superconducting terminals labeled 1, 2, and 0. These terminals form a Y-shaped junction and are used to realize the Josephson diode effect.
Q: What is InAs?
A: InAs stands for Indium Arsenide, which is a semiconductor material commonly used in electronic devices and research experiments.
Q: What is a two-dimensional electron gas (2DEG)?
A: A two-dimensional electron gas (2DEG) refers to a system in which electrons are confined to move in a two-dimensional plane, typically at the interface between two materials.
Q: What does it mean for the 2DEG to be proximitized by an epitaxial aluminum layer?
A: Proximitization refers to the process of bringing a superconductor in close proximity to a normal material or semiconductor, resulting in induced superconducting properties in the latter. In this case, the epitaxial aluminum layer is brought in close proximity to the InAs 2DEG, inducing superconducting behavior in the 2DEG.
Q: What is a synthetic realization?
A: Synthetic realization refers to the creation or generation of a particular effect or phenomenon using controlled techniques or materials, as opposed to relying on the natural occurrence of that effect.
Q: What is the Josephson current-phase relation (CφR)?
A: The Josephson current-phase relation (CφR) describes the relationship between the supercurrent flowing through a Josephson junction and the phase difference across the junction.
Q: What are higher harmonic terms in the Josephson current-phase relation?
A: Higher harmonic terms refer to additional terms in the Josephson current-phase relation that go beyond the fundamental sinusoidal relationship. These terms introduce more complex behavior to the supercurrent and contribute to the Josephson diode effect.
Q: What is the role of the phase difference in the Josephson diode effect?
A: The phase difference, provided by an applied magnetic field, plays a crucial role in the Josephson diode effect. It contributes to the synthetic realization of the Josephson current-phase relation and affects the behavior of the supercurrent flowing through the diode.
Q: How can the diode be switched between positive and negative polarity?
A: The diode can be switched between positive and negative polarity by applying a small out-of-plane magnetic field or by using electrostatic gating. These external influences modify the critical current flowing through the diode in different bias directions.
Q: What is an out-of-plane magnetic field?
A: An out-of-plane magnetic field refers to a magnetic field that is perpendicular to the plane of the device or material under consideration. In the context of the Josephson diode, applying such a field can switch the diode between positive and negative polarity.
Q: What is electrostatic gating?
A: Electrostatic gating involves applying an electric field to control the behavior of charges in a device or material. In the context of the Josephson diode, electrostatic gating can also switch the diode between positive and negative polarity.
