Monopole Josephson effects in Dirac Spin Liquids

Friday Quantum Seminar

Gautam Nambiar (University of Maryland)
Friday, April 1, 2022 - 1:00pm
ATL 2324 and Virtual Via Zoom

Dirac Spin Liquids (DSLs) are gapless symmetric states in 2+1 dimensions with no magnetic order. They are featureless, yet interesting because their low energy physics is believed to be described by QED-3, an effective field theory in terms of gapless Dirac fermions coupled to an emergent U(1) gauge field. They also serve as a parent state for seemingly unrelated magnetically ordered states, where the ordered states arise from condensation of ``monopole excitations” of the DSL. Can such a description have experimentally observable consequences? For example, can we, in theory, induce and measure an emergent electric field inside a DSL? We answer this question in the affirmative by proposing an “Ordered state - DSL - Ordered state” Josephson junction setup. The ordered states can be viewed as condensates of monopoles which can tunnel between the two ordered states through the middle region of DSL. In this talk, we will go through various interesting consequences depending on the choice of ordered states and operations performed on them. One of them is a time-dependent emergent electric field inside the DSL. We propose a way to measure this optically via Raman scattering. In the second part of the talk, we will go back and take a closer look at the field theory operators, (such as monopoles and emergent flux), and describe our attempt to map them to microscopic spin operators.

(Pizza and refreshments will be served after the talk.)