Cryogen-free dilution refrigerator system for studies of superconductor - quantum Hall hybrid samples
Abstract
The past few years have seen an explosive growth of interest to the topological states of matter. Some of these states could host exotic excitations, different from the familiar electrons and holes. The excitations, which include so called ÒMajorana fermionsÓ and non-abelian ÒanyonsÓ, have topological properties that protect them against perturbations from the environment. Usual plagues of semiconductor electronics, such as electron scattering by impurities or lattice vibrations, have little effect on such entities. As a result of this robustness, control over topological excitations would potentially enable Òtopologically protectedÓ quantum computation, which would be immune to environmental decoherence. One of the proposed routes for creating the topological excitations is to couple the more conventional topological materials with superconductivity. Since the quantum Hall effect is a prototypical topological state, multiple theoretical predictions exist about topological excitations that could exist at the quantum Hall - superconductor interfaces. However, for many years, these two effects have been viewed as mutually exclusive. In a recent work, the PIÕs group reported on the first observation of a supercurrent through the quantum Hall state. The team was working with ultra-clean graphene (single atomic monolayer of graphite) encapsulated between two layers of hexagonal boron nitride (BN). The latter material is known to be a particular good choice for shielding graphene from ambient conditions Ð it is chemically stable and has a layered structure very similar to graphite, with half of the carbon atoms substituted by either boron or nitrogen. The demonstrated successful coupling of the two systems brings the dream of the topological quantum computing one step closer to reality. To conduct further research in this area, the PI requests funds for purchasing a cryogen-free dilution refrigerator with a base temperature of 10-15 mK and magnetic fields up to 10 Tesla. These temperatures are 2 to 3 times lower than the base temperature achieved by the PIÕs current instrumentation and thus will allow the PIÕs laboratory to conduct the ambitious scientific program outlined in this proposal. The PI plans to fully dedicate the proposed system to measuring superconductor Ð quantum Hall hybrid samples. The cryogen-free dilution refrigerator will allow graduate students to spend more time working on the challenging low-noise electronic measurements at cryogenic temperatures, contributing to their professional growth.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 16, 2018
- Source ID
- W911NF1710197
Entities
People
- Gleb Finkelstein
Organizations
- Army Contracting Command
- Duke University
- United States Army