Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session X49: Characterizing Quantum Emitters Near SurfacesInvited Live
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Sponsoring Units: DCMP Chair: Annemarie Exarhos, Lafayette Coll |
Friday, March 19, 2021 8:00AM - 8:36AM Live |
X49.00001: Control of NV Center Kinetics and Coherence Invited Speaker: Kai-Mei Fu Single defects in crystals have become promising qubit candidates for quantum network applications due to the combination of long spin coherence times, strong optical coupling to spin states and a solid-state environment for device integration. Critical for harnessing the full potential of defect-based qubits will be controlling their formation and coherence properties. Here I discuss how single defect longitudinal studies can be utilized to directly obtain information on NV formation, disappearance and reorientation mechanisms [1]. The study enables an experimental estimation of the NV reorientation barrier as well as highlights the important role of other defects in NV kinetics, even in “ultra-pure” samples. In the second half of the talk I will focus on the effect of surfaces and implantation damage on the optical properties of NV centers formed by implantation and annealing, including centers integrated in devices [2], and a novel method toward separating the surface and radiation damage contributions to the observed optical spectral diffusion. |
Friday, March 19, 2021 8:36AM - 9:12AM Live |
X49.00002: Optical properties of quantum emitters hosted by van der Waals materials Invited Speaker: Gregory Fuchs Single quantum emitters in van der Waals materials are interesting as bright sources of single photons and potentially as a localized quantum sensors that are sensitive to their local environment at or near a surface. Defects in hexagonal boron nitride (h-BN) and strain-activated single photon emitters in WSe2 have emerged as two prominent examples. In this presentation I will focus on our efforts to understand the optical properties of these emitters. I’ll describe our studies of isolated h-BN defects as they relate to optical polarization, linewidth, host material origin, and activation mechanism. In strain-activated WSe2 quantum emitters, a prominent approach to creating localized strain is to drape WSe2 over a dielectric nanopillar substrate. I’ll describe our recent finding that wrinkles in h-BN/WSe2 bilayers lead to a cleaner optical spectrum and purer single-photon emission that of a nanopillar-based emitter. This work was done in collaboration with Raphaël Daveau, Kumarasiri Konthasinghe, Nick Jungwirth, Tom Vandekerckhove, Jaehong Choi, Nikhil Mathur, Arunabh Mukerjee, Chitraleema Chakraborty, Liangyu Qiu, Zefang Wang, Jie Shan, Kin Fai Mak, and A. Nick Vamivakas. |
Friday, March 19, 2021 9:12AM - 9:48AM Live |
X49.00003: Control of quantum emitters in van der Waals materials via strain and photonic structures Invited Speaker: Vinod Menon In this talk we will discuss our work on realizing quantum emitters in van der Waals (vdW) materials through strain engineering and coupling of these emitters to nanophotonic platforms. Specifically, we will discuss deterministic localization of quantum emitters in hexagonal boron nitride (hBN) via strain engineering and coupling of these emitters to silicon nitride microresonators to enhance their emission. In addition, we will also discuss quantum emitters in two-dimensional transition metal dichalcogenides (TMDs) enhanced via strain. The role of strain in exciton funneling versus defect state brightening will be discussed. |
Friday, March 19, 2021 9:48AM - 10:24AM Live |
X49.00004: Spin dynamics in 3D and 2D Invited Speaker: J. Wrachtrup Solid state spin systems show dynamic processes over a wide rage of timescales. With the invention of well-controlled spin structures, the phase behavior and spin dynamics can be controlled and changed in great detail. In the talk, I will discuss the spin dynamics in small scale spin clusters in 3D spin systems. I will then compare our findings to strictly 2D spin layers, exemplified by nuclear spins in hexagonal boron nitride monolayers. Furthermore, I will show the application of a quantum sensor to measure phases and structure of correlated electron materials. Prominent examples are measurements on two-dimensional spin systems showing ferro- or antiferromagnetic spin order. Phase transitions and novel phases by combining two-dimensional layers with different spin orders can be detected. |
Friday, March 19, 2021 10:24AM - 11:00AM Live |
X49.00005: Optical Polarization of Quantum Emitters in Hexagonal Boron Nitride Invited Speaker: Nicholas Jungwirth Isolated point defects in wide bandgap semiconductors are single photon sources with applications in quantum optics, precision sensing, and quantum information processing technologies. In this talk, I will discuss our progress on identifying and characterizing isolated defects in the Van der Waals material hexagonal boron nitride (h-BN). First, I will briefly introduce confocal fluorescence measurements of isolated defects in h-BN that exhibit single photon emission when excited by sub-bandgap energy light. The temperature dependence of the zero-phonon, single-photon emission from these defects is well-described by a lattice vibration model that considers coupling to low energy, in-plane acoustic phonons. Next, I will discuss the temperature-independent polarization selection rules of these zero-phonon lines (ZPLs) and compare our findings with the predictions of a Huang-Rhys model involving two electronic states. Our survey, which spans the spectral range ~550-740 nm, reveals that, in disagreement with a two-electronic-level model, the absorption and emission dipoles are often misaligned. We relate the dipole misalignment angle (Δθ) of a ZPL to its energy shift from the excitation energy (ΔE) and find that Δθ≈0° when ΔE is less than the maximum single-phonon energy in h-BN and that 0≦Δθ≦90° when ΔE exceeds the maximum single-phonon energy in h-BN. This observation indicates that a two-level Huang-Rhys model succeeds at describing excitations mediated by one phonon but fails at describing excitations requiring multiple phonons. We propose that excitations requiring multiple phonons are inefficient in h-BN and that ZPLs with large ΔE are excited indirectly via an intermediate electronic state. This hypothesis is corroborated by polarization measurements of an individual ZPL excited with two distinct wavelengths that indicate a single ZPL may be excited by multiple mechanisms. |
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