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 F36: Spin in Semiconductors for Quantum Information ScienceFocus Live
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Sponsoring Units: GMAG DMP FIAP DCOMP Chair: Gregory Fuchs, Cornell University |
Tuesday, March 16, 2021 11:30AM - 11:42AM Live |
F36.00001: Magnetism in V doped monolayer ZrS2 Greis Julieth, Zhao Tang, Gabe Lopez-Candales, Peihong Zhang Magnetism in 2D materials have attracted much research attention recently. In this work, we present density functional theory based electronic structure calculations of V doped monolayer ZrS2. Vanadium dopant introduces isolated in-gap intermediate states, facilitating the formation of local magnetic moment. These in-gap impurity states also suggest that magnetism may be controlled/tuned by electric gating or optical means. On the other hand, unlike 3d magnetism which is typically shorted ranged, the substantial long tails of 4d electrons also facilitate long range magnetic coupling. Dopant-concentration-dependent local magnetic moment formation and magnetic coupling are investigated. Effects of defect charge states on the magnetic properties are also investigated. |
Tuesday, March 16, 2021 11:42AM - 11:54AM Live |
F36.00002: Probing spin-polarized band structure of V-doped WSe2 Dinh Loc Duong, Jinbao Jiang, Lan-Anh T. Nguyen, KRISHNA PRASAD DHAKAL, Young-Hee Lee Controlling magnetic properties by tuning carrier concentration is a key feature of diluted ferromagnetic semiconductors, giving possibilities for multifunctional spintronic devices. Here, we report a giant Zeeman shift from the spin-polarized state in tungsten diselenide (WSe2) doped with a small amount of vanadium atoms (~0.15%) by investigating resonant magnetotunneling spectroscopy of a vertical graphite/V-WSe2/graphite heterojunction. The p-type character of the doping state is located near the valence band, substantially shifted under an external magnetic field at 7.8 meV/T with a giant g factor of approximately 135, an order of magnitude higher than that of other 2D magnetic semiconductors. The evidence of the spin-polarized band edges of V-doped WSe2 is also confirmed by circular-polarized photoluminescence. A deep understanding of the nature of the V-WSe2 system provides opportunities for future spintronics based on 2D van der Waals diluted ferromagnetic semiconductors. |
Tuesday, March 16, 2021 11:54AM - 12:06PM Live |
F36.00003: Probing zero-field splitting at spin-1 centers through dc magnetoresistance Stephen R McMillan, Michael Flatté Solid-state spins are promising candidates for quantum sensing and quantum information components due to remarkable spin coherence times. Electrical readout of single spins typically relies on Boltzmann distributed spin polarizations, which necessitate operation at low temperatures and/or high magnetic fields to improve the quality of the single-shot protocol [1]. Alternatively, coupling the coherent evolution with spin correlated transport via spin-polarized contact (or spin-polarized STM) is predicted to generate steady-state indicators of the coherent evolution in the low field (~mT) magnetoresistance without ac fields, even at room temperature [2]. These methods are not limited to spin-half states but can be applied to higher spin manifolds as well. We extend this method to the spin-1 neutral divacancy in 4H-SiC, where measurements of zero-field splittings on the order of GHz are resolvable using applied fields in the range of 50 mT as long as the carrier occupation time at the divacancy exceeds 1 ns. We acknowledge support for this work from DOE BES under Award Number DE-SC0016379. |
Tuesday, March 16, 2021 12:06PM - 12:18PM Live |
F36.00004: Scanning Tunneling Microscopy Studies of Fe on GaAs (110) Surface Rebekah Smith, Cuneyt Sahin, Michael Flatté, Jay A. Gupta The introduction of transition metal impurities into semiconductors allows for the study of magnetic phenomena in a multifunctional host material. Using scanning tunneling microscopy (STM) to study individual magnetic dopants allows for magnetic interactions to be probed on an atomic scale. Here we investigate the interaction of Fe adatoms with a host GaAs (110) surface using STM. A GaAs wafer was cleaved in situ at cryogenic temperatures to reveal a pristine (110) surface. Electron beam evaporation was used to deposit iron adatoms onto the GaAs (110) surface. Upon deposition, the Fe atoms replaced Ga atoms on the surface. STM was used to image the substituted Fe atoms in empty and filled electronic states and to probe the local density of states (LDOS) via differential conductance spectroscopy. The substituted iron show a range of topographic contrast, which is also reflected in the associated differential conductance spectroscopy. This contrast may reflect distinct charge/spin states. In addition, we present topographic images and differential conductance spectroscopy of Fe dimers as a function of spatial separation. We highlight the variations in spectroscopy as the separation distance between the iron atoms in the dimers change. |
Tuesday, March 16, 2021 12:18PM - 12:54PM Live |
F36.00005: Spin relaxation in a silicon-based quantum dot qubit Invited Speaker: Viatcheslav Dobrovitski Electron spins in silicon-based quantum dots show much promise as qubits in future large-scale quantum computation platforms, and simple quantum algorithms have been already implemented. However, an important question remains unanswered, of whether this platform can operate in "hot" conditions, at the temperatures higher than 1 K. Besides fundamental interest, the operating temperature may severely limit the scaling capabilities, because of heat dissipation from the classical control electronics needed for operation of a many-qubit quantum processor. |
Tuesday, March 16, 2021 12:54PM - 1:06PM Live |
F36.00006: Spin-orbit interaction in InSb double quantum dots characterized using dispersive gate sensing Lin Han, Michael Chan, Damaz De Jong, Christian Prosko, Kongyi Li, Ghada Badawy, Erik P. A. M. Bakkers, Leo Kouwenhoven, Jonne Koski, Filip Malinowski, Wolfgang Pfaff We experimentally investigate the consequences of a strong spin orbit interaction in double quantum dot defined in an InSb nanowire. Utilizing dispersive gate sensing, we characterize the tunnel coupling and find the dispersive signal depends on electron charge parity as well as magnitude and direction of the external magnetic field. In particular, we identify the spin-orbit field direction for a number of interdot charge transitions involving different orbitals. We notice that the direction of spin-orbit field is similar for charge transitions corresponding to the same orbitals, but varies randomly between different orbitals, and generally is not perpendicular to the nanowire. |
Tuesday, March 16, 2021 1:06PM - 1:18PM Live |
F36.00007: First-principles calculations of copper vacancy centers in zinc sulfide Cuneyt Sahin, Michael Flatté Transition metal impurities and impurity-vacancy systems in wide-gap semiconductors provide a robust platform for realizing optoelectronic applications and a coherent, room-temperature interface between spins and photons. Here we calculate the electronic and structural properties of copper-vacancy complexes in zinc sulfide (ZnS) within the density functional theory. We fix the well-known band-gap problem using the hybrid functionals and calculate a band gap, which agrees excellently with the experimental value. Zinc is then substitutionally replaced with a copper atom, and the vacancy is formed at one of the neighboring sulfur atoms. We perform the ionic relaxations and calculate the defect formation energies for different charged states. The charge transition levels are also computed from the relaxed final energies, including supercell corrections due to finite-size effects. Finally, we calculate the density of states, orbital projected densities, and electronic band structures of the system to identify states located in the bandgap and determine the characteristics of the system. We show that ZnS with Cu-vacancies could be a promising system in which impurity spin and light interaction can be realized. |
Tuesday, March 16, 2021 1:18PM - 1:30PM Not Participating |
F36.00008: Generalization of the linked cluster expansion computational method for arbitrary pulse sequences Mathieu Ouellet, Danielle Bassett, Lee Bassett Solid-state electron-spin qubits suffer from dipolar interactions with their nuclear spin baths. The nuclear spin bath causes decoherence, but it can also serve as a resource of individually addressable nuclear-spin qubits that can be harnessed for quantum computational power. Since the bath is a large, open quantum system, the dynamical processes taking place within the bath and with the electron-spin qubits are challenging to simulate for general Hamiltonians and control sequences. We present a diagrammatic computational approach to evaluate the central electronic spin problem in the presence of non-Markovian bath dynamics for arbitrary electron spin control sequences. This approach lays the groundwork for new computational capabilities, including tracking various flip-flop processes and designing multiple-pulse dynamical control sequences that display the signature of those processes.We aim to use this computational framework to explore quantum dynamics in open quantum systems. |
Tuesday, March 16, 2021 1:30PM - 1:42PM Live |
F36.00009: Radio-Frequency manipulation of strongly interacting electron-nuclear spin systems. Pablo Zangara, Daniela Pagliero, Jacob Henshaw, Ashok Ajoy, Rodolfo Hector Acosta, Neil Manson, Jeffrey A Reimer, Alexander Pines, Carlos Meriles We use optical spin pumping of NV-hosting diamond to investigate the impact of a continuous radio-frequency (RF) drive on the generation of 13C spin polarization. Since this DNP mechanism is based on electron spin cross relaxation, we particularly address the manipulation of hybrid electron-nuclear (1) spin states. We focus on strongly hyperfine-coupled carbons and experimentally show that sufficiently strong RF excitation during optical spin pumping can invert the sign of the observed nuclear polarization. With the aid of numerical modeling, we interpret this as a consequence of electron-nuclear spin mixing, allowing us to drive RF forbidden transitions between different electron spin manifolds. We interprete this as a form of competition between ‘cross effect’ and ‘solid effect’ in an effective four-level system where initialization derives from NV optical pumping, not temperature. The system response to variable magnetic fields allows us to discuss how this process emerges from a subtle interplay between the number of nuclei featuring a given hyperfine coupling and the type and relative concentrations of paramagnetic defects present in the sample. |
Tuesday, March 16, 2021 1:42PM - 1:54PM Live |
F36.00010: Quantum-impurity relaxometry of magnons in thin films: role of chirality Avinash Rustagi, Iacopo Bertelli, Toeno van der Sar, Pramey Upadhyaya Quantum impurity (QI) relaxometry - measuring the relaxation rate of an impurity spin due to its coupling with magnetic noise - has recently emerged as a sensitive, local, and non-invasive technique for probing condensed matter systems including magnetic materials. Chirality plays a central role in developing a predictive theoretical model for QI-relaxometry of magnons in thin films where the QI (e.g. Nitrogen-vacancy (NV) center) and magnons act as the sensor and generator of chiral magnetic noise, respectively. Here, we present this theory highlighting the role of chirality and show that our theory 1) is in excellent quantitative agreement with recent NV-relaxometry experiments, and 2) predicts crossover between the two NV ESR relaxation rates as a key signature of the chiral coupling between the NV and magnons which is corroborated by new experiments on Nickel thin films interfaced with NV QI. |
Tuesday, March 16, 2021 1:54PM - 2:06PM Live |
F36.00011: Nanoscale features of magnetic dopants in 2D systems with spin-orbit interaction Adonai Rodrigues da Cruz, Michael Flatté The combination of spin-orbit coupling with broken spatial inversion symmetry in semiconductors (e.g. zinc-blende quantum-wells and surfaces) and localized spin states originated from a single magnetic dopant is a promising system to realize future semiconductor spintronics devices. |
Tuesday, March 16, 2021 2:06PM - 2:18PM Live |
F36.00012: Spin-orbit mediated modulation of defect-phonon coupling in transition metal dichalcogenides Chitraleema Chakraborty, Christopher Ciccarino, Prineha Narang The formation of defects is unavoidable in 2D materials with currently available growth techniques. Nevertheless, a myriad of modern optoelectronic and nanophotonic devices leverages on functionalities like single-photon emission from point defects in solid-state materials. In parallel, advances in atomic-resolution imaging techniques provide opportunities to directly create, manipulate, and characterize defects on the atomic scale in 2D materials. Therefore, we present theoretical calculations and analysis of quantum defects in 2D materials. We study the electron-phonon interactions of electronic transitions in defects and quantify their optical efficiency by calculating the Huang-Rhys factor1. This presents a pathway for maximizing their optical efficiency and provides a deterministic choice for defect creation at the atomic scale using scanning probe techniques. |
Tuesday, March 16, 2021 2:18PM - 2:30PM Live |
F36.00013: Electron ground state g-factor in embedded InGaAs quantum dots: An atomistic study Mustafa Kahraman, Ceyhun Bulutay We present atomistic computations within an empirical pseudopotential framework for the electron s-shell ground state g-tensor of embedded InGaAs quantum dots (QDs). A large structural set consisting of geometry, size, molar fraction and strain variations is worked out. The tensor components are observed to show insignificant discrepancies even for the highly anisotropic shapes. The family of g-factor curves associated with these parameter combinations coalesce to a single universal one when plotted as a function of the gap energy, thus confirming a recent assertion using a completely different electronic structure. Moreover, our work extends its validity to alloy QDs with various shapes and finite confinement that allows for penetration to the host matrix as in actual samples. Our set of results for practically relevant InGaAs QDs can help to accomplish through structural control, g-near-zero, or other targeted g values for spintronic or electron spin resonance-based direct quantum logic applications. |
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