# 调整成对量子粒子的键以创造无耗散的流动 精选

https://www.science.org/doi/10.1126/science.abg1110

Following a crossover

Superfluidity in fermionic systems occurs through the pairing of fermions into bosons, which can undergo condensation. Depending on the strength of the interactions between fermions, the pairs range from large and overlapping to tightly bound. The crossover between these two limits has been explored in ultracold Fermi gases. Liu et al. observed the crossover in an electronic system consisting of two layers of graphene separated by an insulating barrier and placed in a magnetic field. In this two-dimensional system, the pairs were excitons formed from an electron in one layer and a hole in the other. The researchers used magnetic field and layer separation to tune the interactions and detected the signatures of superfluidity through transport measurements. —JS

Abstract

In fermionic systems, superconductivity and superfluidity occur through the condensation of fermion pairs. The nature of this condensate can be tuned by varying the pairing strength, which is challenging in electronic systems. We studied graphene double layers separated by an atomically thin insulator. Under applied magnetic field, electrons and holes couple across the barrier to form bound magneto-excitons whose pairing strength can be continuously tuned by varying the effective layer separation. Using temperature-dependent Coulomb drag and counterflow current measurements, we were able to tune the magneto-exciton condensate through the entire phase diagram from weak to strong coupling. Our results establish magneto-exciton condensates in graphene as a model platform to study the crossover between two bosonic quantum condensate phases in a solid-state system.

http://www.blog.sciencetimes.com.cn/blog-212210-1321326.html

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