Article
Materials Science, Multidisciplinary
Zoltan Gyorgy, Andras Palyi, Gabor Szechenyi
Summary: The study investigates a bichromatic EDSR scheme, where two driving tones with different frequencies are used to connect the spin Larmor frequency with the sum of the two drive frequencies. The research suggests that this scheme could be beneficial for a shared-control spin qubit architecture by enabling simultaneous single-qubit gates.
Article
Multidisciplinary Sciences
Ryan M. Jock, N. Tobias Jacobson, Martin Rudolph, Daniel R. Ward, Malcolm S. Carroll, Dwight R. Luhman
Summary: This research demonstrates a method for controlling electron spin qubits on a silicon heterointerface through spin-orbit effects, without the need for complex nanofabrication equipment. The method offers high logic gate orthogonality and long qubit coherence time, while enabling fast control. The study also investigates charge noise in a silicon double quantum dot through dynamical decoupling experiments and evaluates qubit frequency drift and low-frequency noise.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
Chuyao Tong, Annika Kurzmann, Rebekka Garreis, Wei Wister Huang, Samuel Jele, Marius Eich, Lev Ginzburg, Christopher Mittag, Kenji Watanabe, Takashi Taniguchi, Klaus Ensslin, Thomas Ihn
Summary: The study reports experiments on coupled bilayer graphene double quantum dots, where the spin and valley states are precisely controlled, enabling the observation of two-electron combined blockade physics. The switching of selection rules is demonstrated by switching between different ground states with gate and magnetic-field tuning, showing either valley blockade or spin blockade depending on the ground state configuration.
PHYSICAL REVIEW LETTERS
(2022)
Article
Materials Science, Multidisciplinary
D. Krychowski, S. Lipinski
Summary: The study discusses spin polarized transport through a quantum dot coupled to ferromagnetic electrodes with noncollinear magnetizations using nonequilibrium Green functions in the finite-U slave boson mean field approximation. The difference in magnetization orientations of the electrodes opens off diagonal spin-orbital transmission and leads to spin-flip currents. The study also explores the impact of spin-orbit coupling, magnetization orientation, and gate voltage on tunneling magnetoresistance (TMR).
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2022)
Article
Physics, Multidisciplinary
Xinxin Cai, Elliot J. Connors, Lisa F. Edge, John M. Nichol
Summary: Electron spins in silicon quantum dots are excellent qubits due to their long coherence times, high gate fidelities, and compatibility with advanced semiconductor manufacturing techniques. In this study, we demonstrate that spin-valley coupling in Si enables coherent control of single and multi-electron spin states without oscillating electromagnetic fields. Our results establish spin-valley coupling as a promising mechanism for coherent control of qubits based on electron spins in semiconductor quantum dots.
Article
Multidisciplinary Sciences
Jae-Pil So, Ha-Reem Kim, Hyeonjun Baek, Kwang-Yong Jeong, Hoo-Cheol Lee, Woong Huh, Yoon Seok Kim, Kenji Watanabe, Takashi Taniguchi, Jungkil Kim, Chul-Ho Lee, Hong-Gyu Park
Summary: The study demonstrates electrically driven single-photon emitters located at positions induced by local strain gradients on a van der Waals heterostructure. These emitters exhibit excellent emission properties controlled by strain gradients, showcasing potential for integrated quantum light sources.
Article
Multidisciplinary Sciences
J. Yoneda, W. Huang, M. Feng, C. H. Yang, K. W. Chan, T. Tanttu, W. Gilbert, R. C. C. Leon, F. E. Hudson, K. M. Itoh, A. Morello, S. D. Bartlett, A. Laucht, A. Saraiva, A. S. Dzurak
Summary: The article demonstrates high-fidelity coherent transport of an electron spin qubit between quantum dots in isotopically-enriched silicon, with a reported polarization transfer fidelity of 99.97% and an average coherent transfer fidelity of 99.4%. The results suggest that this method can reduce the cost of fault-tolerant quantum processors and provide key elements for high-fidelity, on-chip quantum information distribution.
NATURE COMMUNICATIONS
(2021)
Article
Materials Science, Multidisciplinary
Junpeng Hou, Ya-Jie Wu, Chuanwei Zhang
Summary: The study investigates topological phase transitions driven by non-Hermiticity, showing that transitions from trivial to quantum spin Hall (QSH) insulators can be induced by varying non-Hermitian terms, and exceptional edge arcs exist in QSH phases. Two topological invariants are established for characterizing the non-Hermitian phase transitions, providing a powerful tool for exploring novel non-Hermitian topological matter and their device applications beyond Chern classes.
Article
Energy & Fuels
Yue Sun, Yunbo Dong, Zhixuan Zhu, Lin Li, Caili Dai, Yining Wu, Mingwei Zhao
Summary: This study synthesized active carbon dots (S-CDs) through two-step hydrothermal reactions and demonstrated their potential in reducing injection pressure and improving oil recovery in unconventional reservoirs. The S-CDs were found to possess excellent aqueous dispersibility and resistance to high temperature and salinity, and exhibited effective control over interfacial tension, viscoelastic modulus, wettability alteration, and adsorption capacity. Core flooding tests showed significant reduction in injection pressure and increase in oil recovery rate with 0.05 wt% S-CD nanofluids compared to simulated formation water.
Article
Energy & Fuels
Yue Sun, Yunbo Dong, Zhixuan Zhu, Lin Li, Caili Dai, Yining Wu, Mingwei Zhao
Summary: Carbon-based nanoparticles, known as active carbon dots (S-CDs), were synthesized in this study for their potential in enhancing oil recovery by improving oil-water interfacial activity. The S-CDs exhibited excellent oil-water and oil-solid interfacial activity by controlling interfacial tension, viscoelastic modulus, wettability alteration, and adsorption capacity. Core flooding tests showed a significant reduction in injection pressure and an increase in oil recovery rate when using 0.05 wt% S-CD nanofluids compared to simulated formation water.
Article
Optics
Alvaro Rubio-Garcia, Angel L. Corps, Armando Relano, Rafael A. Molina, Francisco Perez-Bernal, Jose Enrique Garcia-Ramos, Jorge Dukelsky
Summary: This article studies a model of a quantum spin weakly coupled to a spin-polarized Markovian environment, and discovers a special Liouvillian spectral phase. The exceptional phase is composed of second-order exceptional points, and it leads to a slower evolution that cannot be described by exponential decay. This phase is separated from the normal phase by a critical line.
Article
Chemistry, Multidisciplinary
Robin T. K. Schock, Jonathan Neuwald, Wolfgang Moeckel, Matthias Kronseder, Luka Pirker, Maja Remskar, Andreas K. K. Huettel
Summary: It is demonstrated that adding a bismuth semimetal layer between the contact metal and the nanomaterial significantly improves the properties of the contacts, leading to better stability and less trap states.
ADVANCED MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Qiang Cheng, Qing-Feng Sun
Summary: This study investigates the energy spectra of Dirac fermions confined in the quantum dot formed in the graphene/transition metal dichalcogenides (TMD) system under a perpendicular magnetic field. The obtained spin-valley polarized spectra can be classified into three types based on the energy gap values and are strongly influenced by the pseudospin potential and valley-dependent spin-orbit coupling unique to the electronic structure of the graphene/TMD system. The energy spectra exhibit sudden jumps, degeneracy-splitting-recombination behaviors, and continuous changes due to the Berry phase jumps and continuous change of the Berry phase. The evolutions of the levels by adjusting the valley-dependent spin-orbit coupling and pseudospin potential are also studied. These findings suggest the possibility of controlling the specific spin-valley freedom of electrons in the graphene/TMD system using a quantum dot setup.
Article
Materials Science, Multidisciplinary
Ahmal Jawad Zafar, Aranyo Mitra, Vadym Apalkov
Summary: In this study, the electron dynamics of a graphene nanoring in the presence of an ultrashort optical pulse were theoretically investigated. It was found that circularly polarized pulses can induce valley polarization in the graphene nanoring, whereas no valley polarization is observed in a graphene monolayer. The magnitude of the valley polarization in the graphene nanoring depends on the system parameters.
Article
Chemistry, Physical
Charles Babin, Rainer Stoehr, Naoya Morioka, Tobias Linkewitz, Timo Steidl, Raphael Woernle, Di Liu, Erik Hesselmeier, Vadim Vorobyov, Andrej Denisenko, Mario Hentschel, Christian Gobert, Patrick Berwian, Georgy Astakhov, Wolfgang Knolle, Sridhar Majety, Pranta Saha, Marina Radulaski, Nguyen Tien Son, Jawad Ul-Hassan, Florian Kaiser, Joerg Wrachtrup
Summary: Optically addressable spin defects in silicon carbide (SiC) are a promising platform for quantum information processing, enabling high-fidelity spin qubit operations. However, degradation of spin-optical coherence after integration in nanophotonic structures poses a challenge for scalability towards large-scale quantum networks.
Correction
Engineering, Electrical & Electronic
Alina Mrenca-Kolasinska, Krzysztof Kolasinski, Bartlomiej Szafran
SEMICONDUCTOR SCIENCE AND TECHNOLOGY
(2022)
Article
Multidisciplinary Sciences
Bartlomiej Rzeszotarski, Alina Mrenca-Kolasinska, Francois M. Peeters, Bartlomiej Szafran
Summary: The transconductance and effective Lande g* factors for a quantum point contact defined in silicene by the electric field of a split gate are investigated. The strong spin-orbit coupling in buckled silicene reduces the g* factor for in-plane magnetic field, but enhances it for perpendicular magnetic field. The main contribution to the Zeeman splitting comes from the intrinsic spin-orbit coupling defined by the Kane-Mele form of interaction.
SCIENTIFIC REPORTS
(2021)
Article
Materials Science, Multidisciplinary
Alina Mrenca-Kolasinska, Peter Rickhaus, Giulia Zheng, Klaus Richter, Thomas Ihn, Klaus Ensslin, Ming-Hao Liu
Summary: Researchers have developed a self-consistent quantum capacitance model to study the electrostatics of large-angle twisted bilayer graphene (tBLG) and have extended it to other graphene systems. They have also proposed a new experiment that utilizes the decoupling effect to control the bandgap in bilayer graphene.
Article
Physics, Applied
Edyta N. Osika, Sacha Kocsis, Yu-Ling Hsueh, Serajum Monir, Cassandra Chua, Hubert Lam, Benoit Voisin, Michelle Y. Simmons, Sven Rogge, Rajib Rahman
Summary: This study proposes a method to couple microwave photons to atomically precise donor spin-qubit devices in silicon using the hyperfine interaction intrinsic to donor systems and an electrically induced spin-orbit coupling. The research shows that strong spin-photon coupling can be achieved in realistic device conditions without the need for an external magnetic field gradient through characterization and estimation of the 1P-1P system.
PHYSICAL REVIEW APPLIED
(2022)
Article
Chemistry, Multidisciplinary
Matthew B. Donnelly, Mushita M. Munia, Joris G. Keizer, Yousun Chung, A. M. Saffat-Ee Huq, Edyta N. Osika, Yu-Ling Hsueh, Rajib Rahman, Michelle Y. Simmons
Summary: Controlling electron tunneling is crucial in the design and operation of semiconductor nanostructures, especially in quantum computing devices. This study successfully combines scanning tunneling microscopy lithography and tight-binding non-equilibrium Green's function (TB-NEGF) modeling to accurately describe the dependence of tunnel junction resistance on junction length, achieving satisfactory results. The use of TB-NEGF formalism in accurately modeling highly doped, atomically precise tunnel junctions in silicon is confirmed, and this model has potential for improving device performance at the nanoscale.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Tanmay Thakur, Bartlomiej Szafran
Summary: We studied vortices in Wigner molecules formed in the laboratory frame induced by anisotropy of the external potential or electron effective mass. The behavior of the vortices is influenced by the anisotropy of the electron effective mass. In anisotropic systems, the ground state vortex structure undergoes continuous evolution with varying magnetic field, while in isotropic systems, it changes rapidly at angular momentum transitions. The additional vortices first appear on the edges of the confined system far from the axis of a linear Wigner molecule in fractional quantum Hall conditions.
SCIENTIFIC REPORTS
(2023)
Article
Physics, Applied
M. Amir Bazrafshan, Farhad Khoeini, Bartlomiej Szafran
Summary: This work examines the electronic and transport properties of phosphorene nanorings in two perpendicular directions (zigzag and armchair directions) with zigzag metallic source and drain leads. The study shows that system parameters such as the radius of the rings, the width of the leads, and the external potential affect the electronic transport. Results indicate the existence of a transport energy gap that can be adjusted by the width of the leads and the radius of the nanoring. The wider leads are more sensitive to changes in the inner radius, and the transport along the armchair direction is more tunable than along the zigzag direction. The effects of external potentials on conductance are more significant than geometric parameters.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Nanoscience & Nanotechnology
Juan I. Climente, Bartlomiej Szafran
Summary: Calculations reveal that the photophysics of HgTe nanoplatelets are largely governed by the Gamma(6) - Gamma(8) band coupling, leading to a size-dependent energy spectrum and charge distribution. The thick HgTe NPLs with small band gap and large exciton binding energy suggest the potential for an excitonic insulator phase.
Article
Materials Science, Multidisciplinary
Tanmay Thakur, Bartlomiej Szafran
Summary: This study investigates the Wigner crystallization of electron systems in phosphorene quantum dots with circular and elongated geometries. The findings show that the large effective masses in phosphorene promote electron charge separation in relatively small quantum dots. The anisotropy of the effective mass allows for the formation of Wigner molecules with lower symmetry. It is also observed that circular quantum dots exhibit single-electron islands for two and four confined electrons, but not for three trapped carriers. The study discusses the spectral signatures of Wigner crystallization and the characteristics of systems with Wigner molecule states.
Article
Materials Science, Multidisciplinary
Edyta N. Osika, Samuel K. Gorman, Serajum Monir, Yu-Ling Hsueh, Marcus Borscz, Helen Geng, Brandur Thorgrimsson, Michelle Y. Simmons, Rajib Rahman
Summary: Recent research has shown that high-fidelity readout of singlet-triplet qubits can be achieved in silicon-based multidonor quantum dot systems using shelving and latched readout techniques. Shelving readout requires a calibration step to account for time-varying nuclear spin polarization, while latched readout maintains non-zero readout visibility even in the presence of nuclear spin flips.
Article
Materials Science, Multidisciplinary
Bartlomiej Szafran
Summary: A variational approach was used to study the localization of a neutral exciton in a two-dimensional crystal. The results showed that when the potential step was small, the exciton occupied a larger area than the nominal width of the junction, and the localization position was linearly related to the potential step size.
Article
Materials Science, Multidisciplinary
Tanmay Thakur, Bartlomiej Szafran
Summary: The Aharonov-Bohm effect on a confined electron ground state in a quantum ring defined electrostatically within the phosphorene monolayer is studied. The strong anisotropy of effective masses in phosphorene quenches ground-state oscillations, but an elliptic deformation can compensate for this effect. By determining the appropriate ratio of semiaxes, the spectrum becomes identical to that of a circular quantum ring.
Article
Materials Science, Multidisciplinary
Archana Tankasala, Benoit Voisin, Zachary Kembrey, Joseph Salfi, Yu-Ling Hsueh, Edyta N. Osika, Sven Rogge, Rajib Rahman
Summary: This study investigates the two-electron states and exchange couplings for a phosphorous donor pair in silicon. The researchers used an atomistic full configuration interaction method to analyze donor separations and found three distinct donor separation regimes. The study also assessed the validity of simplified methods and examined the effects of donor depth on exchange couplings.
Article
Materials Science, Multidisciplinary
Shiang-Bin Chiu, Alina Mrenca-Kolasinska, Ka Long Lei, Ching-Hung Chiu, Wun-Hao Kang, Szu-Chao Chen, Ming-Hao Liu
Summary: Graphene, with its similar dispersion relation to photons, has great potential for applications in electron optics. By varying the carrier density with external gates, it is possible to create electron waveguides similar to optical fibers, and by confining the carriers in bipolar junctions, transverse guiding modes can be formed. Waveguides created by gating graphene with carbon nanotubes (CNTs) can produce sharp conductance plateaus and have potential applications in Aharonov-Bohm and two-path interferometers, as well as carrier injection in graphene. The versatility of CNT-induced waveguides allows for various possibilities in manipulating electrons in graphene-based devices.
Article
Materials Science, Multidisciplinary
Fahimeh Norouzi, Mohsen Farokhnezhad, Mahdi Esmaeilzadeh, Bartlomiej Szafran
Summary: The study shows that spin filtering occurs in borophene nanoribbons exposed to a nonlocal exchange magnetic field, with the spin direction of transmitted electrons being controlled by adjusting the energy of incoming electrons with an external backgate voltage. Additionally, armchair borophene nanoribbons exhibit half-metallic properties in the presence of both a transverse electric field and a nonlocal exchange field.
