Optomechanical coupling between a multilayer graphene mechanical resonator and a superconducting microwave cavity

Abstract

The combination of low mass density, high frequency, and high quality-factor of mechanical resonators made of two-dimensional crystals such as graphene 1-8 make them attractive for applications in force sensing/mass sensing, and exploring the quantum regime of mechanical motion. Microwave optomechanics with superconducting cavities 9-14 offers exquisite position sensitivity 10 and enables the preparation and detection of mechanical systems in the quantum ground state 15,16 . Here, we demonstrate coupling between a multilayer graphene resonator with quality factors up to 220,000 and a high-Q superconducting cavity. Using thermo-mechanical noise as calibration, we achieve a displacement sensitivity of 17 fm/ √ Hz. Optomechanical coupling is demonstrated by optomechanically induced reflection (OMIR) and absorption (OMIA) of microwave photons [17][18][19] . We observe 17 dB of mechanical microwave amplification 13 and signatures of strong optomechanical backaction. We extract the cooperativity C, a characterization of coupling strength, quantitatively from the measurement with no free parameters and find C = 8, promising for the quantum regime of graphene motion. Here, we present a multilayer graphene mechanical resonator coupled to a superconducting cavity. Using a deterministic all-dry transfer technique 22 and a novel microwave coupling design, we are able to combine these two without sacrificing the exceptional intrinsic properties of either. Although multilayer graphene has a higher mass than a monolayer, it could be advantageous for coupling to a superconducting cavity due to its lower electrical resistance. In Figure 2, we characterize the mechanical properties of the multilayer graphene resonator using a homodyne measurement scheme 9 . Here, the cavity is used as an interferometer to detect motion while injecting a microwave signal near ω c and exciting the mechanical resonator with an AC voltage applied to the gate. The mechanical resonance frequency is much larger than the cavity linewidth (ω m /κ ∼ 150), placing us in the sideband resolved limit, a prerequisite for ground state cooling. The cavity can also be used to detect the undriven motion, such as thermomechanical noise of the drum shown in the inset of Figure 2(a) corresponding to a mechanical mode temperature of 96 mK (see SI for additional details). The thermal motion peak serves as a calibration for the displacement sensitivity. While driving the cavity at its resonance and utilizing its full dynamic range before the electrical nonlinearity set in (-41 dBm injected power) we estimate a displacement sensitivity for mechanical motion of 17 fm/ √ Hz. Using a DC voltage applied to the gate electrode, we can also tune the frequency of the multilayer graphene resonator shown in Figure 2(b). The decrease in resonance frequency ω m for non-zero gate voltage is due to electrostatic softening of the spring constant and has been observed before 3 .In Figure 3, we demonstrate optomechanical coupling between the multilayer graphene mechanical resona...

Molybdenum-rhenium alloy based high-Q superconducting microwave resonators

“…Its highly disordered nature of MoRe makes it attractive for kinetic inductance detectors 8 . It makes highly transparent superconducting contacts with carbon nanotubes 22 and has been used to make contact with graphene in forming a high quality-factor superconducting opto-mechanical device 23 . Furthermore, a high upper critical magnetic field 6 makes it attractive for applications requiring magnetic field.…”

Optomechanics with a polarization nondegenerate cavity

“…[5] for a review. Also, the source of electromagnetic radiation varies greatly, ranging from the microwave [6,7] to the optical domain [8][9][10][11]. Each device and setup has its own advantages.…”

Monolayer graphene as dissipative membrane in an optical resonator

“…Hence, a graphene membrane will cause a position-dependent dissipation of the intra-cavity field, which is wavelengthindependent within the visible to near infra-red spectral range. In contrast to standard dispersive optomechanical coupling [12], a predominantly dissipative coupling between membrane and cavity field could allow for efficient laser cooling of the membrane's motion even outside the resolved sideband regime [17,18].Recently, graphene has been optomechanically coupled to superconducting microwave cavities [15] and to the evanescent field of an optical microsphere-resonator [19], however, in both cases the spatial structure of the electromagnetic field was not resolved in the coupling. Here we present an experimental study of a free-standing layer of graphene inside a Fabry-Perot resonator.…”

“…Owing to their low mass and high stiffness they promise higher vibrational frequencies [14,15] than SiN membranes, which is of great interest for future graphene-based optomechanical applications. Another key difference between membranes made of graphene and those made of SiN is the nature of the light-matter coupling.…”