Pub Date : 2024-09-03DOI: 10.1103/physrevapplied.22.034005
Mylène Sauty, Cameron W. Johnson, Tanay Tak, Wan Ying Ho, Yi Chao Chow, James S. Speck, Andreas K. Schmid, Claude Weisbuch, Jacques Peretti
Low-energy electron microscopy (LEEM) was performed on - samples during in situ cesium deposition. LEEM images of electron reflectivity recorded as a function of the incident electron energy at different coverages allowed to spatially resolve the evolution of the local work function (WF) during the activation process. While the average WF drops by more than 3 eV, the local WF remains quite uniform across the surface throughout the activation process. Maximum fluctuations of less than 0.2 eV were observed in the WF maps for coverage of a fraction of a monolayer. These fluctuations are mainly related to the surface topography, in particular, to the atomic steps’ structure, which replicates the substrate miscut. Apart from these weak spatial fluctuations, no clusters that would induce strong local WF contrast were observed at the scale of the 20-nm resolution of the measurements. These observations agree with the simple model of semiconductor activation to negative electron affinity that describes the formation of a dipole layer as responsible for the lowering of the WF. Additionally, at complete coverage, the WF becomes fully homogeneous over the surface, smoothing out features originating from defects and topography.
{"title":"Investigation of the cesium activation of GaN photocathodes by low-energy electron microscopy","authors":"Mylène Sauty, Cameron W. Johnson, Tanay Tak, Wan Ying Ho, Yi Chao Chow, James S. Speck, Andreas K. Schmid, Claude Weisbuch, Jacques Peretti","doi":"10.1103/physrevapplied.22.034005","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.034005","url":null,"abstract":"Low-energy electron microscopy (LEEM) was performed on <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>p</mi></math>-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mrow><mi>Ga</mi><mi mathvariant=\"normal\">N</mi></mrow></math> samples during <i>in situ</i> cesium deposition. LEEM images of electron reflectivity recorded as a function of the incident electron energy at different <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Cs</mi></math> coverages allowed to spatially resolve the evolution of the local work function (WF) during the activation process. While the average WF drops by more than 3 eV, the local WF remains quite uniform across the surface throughout the activation process. Maximum fluctuations of less than 0.2 eV were observed in the WF maps for <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Cs</mi></math> coverage of a fraction of a monolayer. These fluctuations are mainly related to the surface topography, in particular, to the atomic steps’ structure, which replicates the substrate miscut. Apart from these weak spatial fluctuations, no <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Cs</mi></math> clusters that would induce strong local WF contrast were observed at the scale of the 20-nm resolution of the measurements. These observations agree with the simple model of semiconductor activation to negative electron affinity that describes the formation of a dipole layer as responsible for the lowering of the WF. Additionally, at complete <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Cs</mi></math> coverage, the WF becomes fully homogeneous over the surface, smoothing out features originating from defects and topography.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-30DOI: 10.1103/physrevapplied.22.024076
Romaine Kerjouan, Michael Rosticher, Aurélie Pierret, Kenji Watanabe, Takashi Taniguchi, Sukhdeep Dhillon, Robson Ferreira, Daniel Dolfi, Mark Goerbig, Bernard Plaçais, Juliette Mangeney
The sharp Dirac cone of electronic dispersion confers to graphene a remarkable sensitivity to strain. It is usually encoded in scalar and pseudovector potentials, induced by the modification of hopping parameters, which have given rise to new phenomena at the nanoscale, such as giant pseudomagnetic fields and valley polarization. Here, we unveil the effect of these potentials on the quantum transport across a succession of strain-induced barriers. We use high-mobility -–encapsulated graphene, transferred over a large () crenelated - substrate. We show the emergence of a broad resistance ancillary peak at positive energy that arises from Klein-tunneling barriers induced by the tensile strain at the trench edges. Our theoretical study, in agreement with experiment, quantitatively highlights the balanced contributions of strain-induced scalar and pseudovector potentials on ballistic transport. Our results establish crenelated van der Waals heterostructures as a promising platform for strain engineering in view of applications and basic physics.
{"title":"Quantum transport signature of strain-induced scalar and pseudovector potentials in a crenelated h-BN/graphene heterostructure","authors":"Romaine Kerjouan, Michael Rosticher, Aurélie Pierret, Kenji Watanabe, Takashi Taniguchi, Sukhdeep Dhillon, Robson Ferreira, Daniel Dolfi, Mark Goerbig, Bernard Plaçais, Juliette Mangeney","doi":"10.1103/physrevapplied.22.024076","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024076","url":null,"abstract":"The sharp Dirac cone of electronic dispersion confers to graphene a remarkable sensitivity to strain. It is usually encoded in scalar and pseudovector potentials, induced by the modification of hopping parameters, which have given rise to new phenomena at the nanoscale, such as giant pseudomagnetic fields and valley polarization. Here, we unveil the effect of these potentials on the quantum transport across a succession of strain-induced barriers. We use high-mobility <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>h</mi></math>-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>BN</mi></math>–encapsulated graphene, transferred over a large (<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>10</mn><mo>×</mo><mn>10</mn><mspace width=\"0.2em\"></mspace><mtext fontfamily=\"times\">μ</mtext><msup><mrow><mi mathvariant=\"normal\">m</mi></mrow><mn>2</mn></msup></math>) crenelated <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>h</mi></math>-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>BN</mi></math> substrate. We show the emergence of a broad resistance ancillary peak at positive energy that arises from Klein-tunneling barriers induced by the tensile strain at the trench edges. Our theoretical study, in agreement with experiment, quantitatively highlights the balanced contributions of strain-induced scalar and pseudovector potentials on ballistic transport. Our results establish crenelated van der Waals heterostructures as a promising platform for strain engineering in view of applications and basic physics.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224251","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-30DOI: 10.1103/physrevapplied.22.024075
Maximilian W. Feil, Magdalena Weger, Hans Reisinger, Thomas Aichinger, André Kabakow, Dominic Waldhör, Andreas C. Jakowetz, Sven Prigann, Gregor Pobegen, Wolfgang Gustin, Michael Waltl, Michel Bockstedte, Tibor Grasser
Fully processed SiC power MOSFETs emit light during switching of the gate terminal, while the drain and source terminals are both grounded. The emitted photons are caused by defect-assisted recombination of electrons and holes at the - interface, and can be detected through the SiC substrate. Here we present time-gated spectroscopic characterization of these interfacial point defects. Unlike in previous studies, the devices were opened in such a way that the drain contact remained electrically active. A separate examination of the photons emitted at the rising and falling transitions of the gate-source voltage enabled the extraction of two different spectral components. One of these components consists of a single transition with phonon replicas of a local vibrational mode with an astonishingly high energy of 220 meV—well above the highest phonon modes in -SiC and of 120 and 137 meV, respectively. On the basis of a quantum mechanical model, we successfully fitted its emission spectrum and assigned it to donor-acceptor-pair recombination involving a carbon-cluster-like defect. Other transitions were assigned to -assisted, -D, and nitrogen-aluminum donor-acceptor-pair recombination. Because of the relevance of these defects in the operation of SiC MOSFETs, these insights will contribute to improved reliability and performance of these devices.
{"title":"Time-gated optical spectroscopy of field-effect-stimulated recombination via interfacial point defects in fully processed silicon carbide power MOSFETs","authors":"Maximilian W. Feil, Magdalena Weger, Hans Reisinger, Thomas Aichinger, André Kabakow, Dominic Waldhör, Andreas C. Jakowetz, Sven Prigann, Gregor Pobegen, Wolfgang Gustin, Michael Waltl, Michel Bockstedte, Tibor Grasser","doi":"10.1103/physrevapplied.22.024075","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024075","url":null,"abstract":"Fully processed SiC power MOSFETs emit light during switching of the gate terminal, while the drain and source terminals are both grounded. The emitted photons are caused by defect-assisted recombination of electrons and holes at the <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>4</mn><mi>H</mi></math>-<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>([A-Z][a-z])([A-Z])</mi><mo>/</mo><msub><mi>([A-Z][a-z])([A-Z])</mi><mn>2</mn></msub></math> interface, and can be detected through the SiC substrate. Here we present time-gated spectroscopic characterization of these interfacial point defects. Unlike in previous studies, the devices were opened in such a way that the drain contact remained electrically active. A separate examination of the photons emitted at the rising and falling transitions of the gate-source voltage enabled the extraction of two different spectral components. One of these components consists of a single transition with phonon replicas of a local vibrational mode with an astonishingly high energy of 220 meV—well above the highest phonon modes in <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>4</mn><mi>H</mi></math>-SiC and <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>([A-Z][a-z])([A-Z])</mi><mn>2</mn></msub></math> of 120 and 137 meV, respectively. On the basis of a quantum mechanical model, we successfully fitted its emission spectrum and assigned it to donor-acceptor-pair recombination involving a carbon-cluster-like defect. Other transitions were assigned to <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>EH</mi><mrow><mrow><mn>6</mn><mo>/</mo><mn>7</mn></mrow></mrow></msub></math>-assisted, <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>EK</mi><mn>2</mn></msub></math>-D, and nitrogen-aluminum donor-acceptor-pair recombination. Because of the relevance of these defects in the operation of SiC MOSFETs, these insights will contribute to improved reliability and performance of these devices.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-30DOI: 10.1103/physrevapplied.22.024077
Panu Hildén, Andriy Shevchenko
For many photonic devices, crosstalk between densely packed waveguides poses a major problem leading to unreliable or inefficient operation of the device. In this work, a general method for modeling the crosstalk, not only in straight waveguide arrays but also in curved ones, is introduced. The method is based on a matrix analysis of electromagnetic field coupling between closely spaced waveguides. As an example, we show how bending of waveguides in an array reduces the crosstalk. The approach can help overcome the crosstalk problem in a variety of photonic integrated devices, including phased waveguide arrays, arrayed waveguide gratings, optical multiplexers, and high-density interconnects between optical and electronic components.
{"title":"Matrix analysis of high-density arrayed waveguides: Crosstalk suppression by bending","authors":"Panu Hildén, Andriy Shevchenko","doi":"10.1103/physrevapplied.22.024077","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024077","url":null,"abstract":"For many photonic devices, crosstalk between densely packed waveguides poses a major problem leading to unreliable or inefficient operation of the device. In this work, a general method for modeling the crosstalk, not only in straight waveguide arrays but also in curved ones, is introduced. The method is based on a matrix analysis of electromagnetic field coupling between closely spaced waveguides. As an example, we show how bending of waveguides in an array reduces the crosstalk. The approach can help overcome the crosstalk problem in a variety of photonic integrated devices, including phased waveguide arrays, arrayed waveguide gratings, optical multiplexers, and high-density interconnects between optical and electronic components.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1103/physrevapplied.22.024073
Grégoire Pichard, Desiree Lim, Étienne Bloch, Julien Vaneecloo, Lilian Bourachot, Gert-Jan Both, Guillaume Mériaux, Sylvain Dutartre, Richard Hostein, Julien Paris, Bruno Ximenez, Adrien Signoles, Antoine Browaeys, Thierry Lahaye, Davide Dreon
We report on the trapping of single rubidium atoms in large arrays of optical tweezers comprising up to 2088 sites in a cryogenic environment at . Our approach relies on the use of microscope objectives that are in vacuum but at room temperature, in combination with windowless thermal shields into which the objectives are protruding to ensure a cryogenic environment for the trapped atoms. To achieve enough optical power for efficient trapping, we combine two lasers at slightly different wavelengths. We discuss the performance and limitations of our design. Finally, we demonstrate atom-by-atom rearrangement of an 828-atom target array using moving optical tweezers controlled by a field-programmable gate array.
{"title":"Rearrangement of individual atoms in a 2000-site optical-tweezer array at cryogenic temperatures","authors":"Grégoire Pichard, Desiree Lim, Étienne Bloch, Julien Vaneecloo, Lilian Bourachot, Gert-Jan Both, Guillaume Mériaux, Sylvain Dutartre, Richard Hostein, Julien Paris, Bruno Ximenez, Adrien Signoles, Antoine Browaeys, Thierry Lahaye, Davide Dreon","doi":"10.1103/physrevapplied.22.024073","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024073","url":null,"abstract":"We report on the trapping of single rubidium atoms in large arrays of optical tweezers comprising up to 2088 sites in a cryogenic environment at <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mn>6</mn><mspace width=\"0.2em\"></mspace><mtext>K</mtext></math>. Our approach relies on the use of microscope objectives that are in vacuum but at room temperature, in combination with windowless thermal shields into which the objectives are protruding to ensure a cryogenic environment for the trapped atoms. To achieve enough optical power for efficient trapping, we combine two lasers at slightly different wavelengths. We discuss the performance and limitations of our design. Finally, we demonstrate atom-by-atom rearrangement of an 828-atom target array using moving optical tweezers controlled by a field-programmable gate array.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1103/physrevapplied.22.024071
Akihiko Sekine, Mari Ohfuchi, Yoshiyasu Doi
The quantum transduction between microwave and optical photons is essential for realizing scalable quantum computers with superconducting qubits. Due to the large frequency difference between microwave and optical ranges, the transduction needs to be done via intermediate bosonic modes or nonlinear processes. So far, the transduction efficiency via the magneto-optic Faraday effect (i.e., the light-magnon interaction) in the ferromagnet YIG has been demonstrated to be as small as due to the weak magneto-optic coupling. Here, we take advantage of the fact that three-dimensional topological insulator thin films exhibit a topological Faraday effect that is independent of the sample thickness in the terahertz regime. This leads to a large Faraday rotation angle and therefore enhanced light-magnon interaction in the thin-film limit. We show theoretically that the transduction efficiency between microwave and terahertz photons can be greatly improved to by utilizing the heterostructures consisting of topological insulator thin films, such as and ferromagnetic insulator thin films, such as YIG.
微波光子和光学光子之间的量子转换对于实现具有超导量子比特的可扩展量子计算机至关重要。由于微波和光学范围之间的频率差异很大，因此需要通过中间玻色子模式或非线性过程来实现量子转换。迄今为止，由于磁光耦合较弱，在铁磁体 YIG 中通过磁光法拉第效应（即光磁子相互作用）实现的转导效率 η 已被证明小至 η∼10-8-10-15 。在这里，我们利用了三维拓扑绝缘体薄膜在太赫兹机制下表现出与样品厚度无关的拓扑法拉第效应这一事实。这导致了较大的法拉第旋转角，从而增强了薄膜极限的光磁相互作用。我们从理论上证明，利用由拓扑绝缘体薄膜（如 Bi2Se3）和铁磁绝缘体薄膜（如 YIG）组成的异质结构，微波和太赫兹光子之间的传输效率可以大大提高到 η∼10-4。
{"title":"Microwave-to-optical quantum transduction utilizing the topological Faraday effect of topological-insulator heterostructures","authors":"Akihiko Sekine, Mari Ohfuchi, Yoshiyasu Doi","doi":"10.1103/physrevapplied.22.024071","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024071","url":null,"abstract":"The quantum transduction between microwave and optical photons is essential for realizing scalable quantum computers with superconducting qubits. Due to the large frequency difference between microwave and optical ranges, the transduction needs to be done via intermediate bosonic modes or nonlinear processes. So far, the transduction efficiency <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>η</mi></math> via the magneto-optic Faraday effect (i.e., the light-magnon interaction) in the ferromagnet YIG has been demonstrated to be as small as <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>η</mi><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>8</mn></mrow></msup><mo>−</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>15</mn></mrow></msup></math> due to the weak magneto-optic coupling. Here, we take advantage of the fact that three-dimensional topological insulator thin films exhibit a topological Faraday effect that is independent of the sample thickness in the terahertz regime. This leads to a large Faraday rotation angle and therefore enhanced light-magnon interaction in the thin-film limit. We show theoretically that the transduction efficiency between microwave and terahertz photons can be greatly improved to <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>η</mi><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> by utilizing the heterostructures consisting of topological insulator thin films, such as <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>Bi</mi><mn>2</mn></msub><msub><mi>Se</mi><mn>3</mn></msub></math> and ferromagnetic insulator thin films, such as YIG.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185316","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1103/physrevapplied.22.024072
Sho Nagase, Shoki Nezu, Koji Sekiguchi
The experimental realization of a spin-wave reservoir chip employing ferromagnetic permalloy thin films is presented. The novel device facilitates the interference of three spherical wave-excited surface mode spin waves within a rectangular waveguide via strategically positioned slits, enabling the detection of electrical signals from surface mode spin waves across all four observation antennas. Through the experiments conducted, it is confirmed that the device functions as a one-input, four-output reservoir capable of estimating external magnetic fields. Notably, the results demonstrate the device’s capacity to retain memory up to one step prior in short-term memory tasks, while confirming the effectiveness of spin-wave interference induced by Huygens slits in enhancing nonlinearity, as observed in parity-check tasks. Furthermore, the inclusion of additional detection antennas contributes to improved learning accuracy, highlighting the significant progress achieved by the spin-wave reservoir chip. These findings underscore substantial progress toward practical implementation, with promising avenues for further development and refinement, showing its remarkable ability to process signals at high speeds, even with 0.8-ns pulse sequences.
{"title":"Spin-wave reservoir chips with short-term memory for high-speed estimation of external magnetic fields","authors":"Sho Nagase, Shoki Nezu, Koji Sekiguchi","doi":"10.1103/physrevapplied.22.024072","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024072","url":null,"abstract":"The experimental realization of a spin-wave reservoir chip employing ferromagnetic permalloy thin films is presented. The novel device facilitates the interference of three spherical wave-excited surface mode spin waves within a rectangular waveguide via strategically positioned slits, enabling the detection of electrical signals from surface mode spin waves across all four observation antennas. Through the experiments conducted, it is confirmed that the device functions as a one-input, four-output reservoir capable of estimating external magnetic fields. Notably, the results demonstrate the device’s capacity to retain memory up to one step prior in short-term memory tasks, while confirming the effectiveness of spin-wave interference induced by Huygens slits in enhancing nonlinearity, as observed in parity-check tasks. Furthermore, the inclusion of additional detection antennas contributes to improved learning accuracy, highlighting the significant progress achieved by the spin-wave reservoir chip. These findings underscore substantial progress toward practical implementation, with promising avenues for further development and refinement, showing its remarkable ability to process signals at high speeds, even with 0.8-ns pulse sequences.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1103/physrevapplied.22.024074
Muhammad Qasim Khan, Wenzheng Dong, Leigh M. Norris, Lorenza Viola
Characterizing temporally correlated noise and “non-Markovian” qubit dynamics is a key prerequisite for achieving noise-tailored error mitigation and optimal device performance. Quantum noise spectroscopy can provide quantitative estimation of the noise spectral features; however, in its current form it is highly vulnerable to implementation nonidealities, notably, state preparation and measurement (SPAM) errors. Further to that, existing protocols have been mostly developed for dephasing-dominated noise processes, with competing dephasing and relaxation effects being largely unaccounted for. We introduce quantum noise spectroscopy protocols inspired by spin-locking techniques that enable the characterization of arbitrary temporally correlated multiaxis noise on a qubit with fixed energy splitting, while remaining resilient to realistic static SPAM errors. By validating the performance of our protocol in both numerical simulation and on cloud-based IBM quantum processors, we demonstrate the successful separation and estimation of native noise spectrum components as well as SPAM error rates. We find that SPAM errors can significantly alter or mask important noise features, with spectra overestimated by up to 26.4% in a classical noise regime. Clear signatures of nonclassical noise are manifest in the reconstructed IBM-qubit dephasing spectra, once SPAM-error effects are compensated for. Our work provides a timely tool for benchmarking realistic sources of noise in qubit devices.
{"title":"Multiaxis quantum noise spectroscopy robust to errors in state preparation and measurement","authors":"Muhammad Qasim Khan, Wenzheng Dong, Leigh M. Norris, Lorenza Viola","doi":"10.1103/physrevapplied.22.024074","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024074","url":null,"abstract":"Characterizing temporally correlated noise and “non-Markovian” qubit dynamics is a key prerequisite for achieving noise-tailored error mitigation and optimal device performance. Quantum noise spectroscopy can provide quantitative estimation of the noise spectral features; however, in its current form it is highly vulnerable to implementation nonidealities, notably, state preparation and measurement (SPAM) errors. Further to that, existing protocols have been mostly developed for dephasing-dominated noise processes, with competing dephasing and relaxation effects being largely unaccounted for. We introduce quantum noise spectroscopy protocols inspired by spin-locking techniques that enable the characterization of arbitrary temporally correlated multiaxis noise on a qubit with fixed energy splitting, while remaining resilient to realistic static SPAM errors. By validating the performance of our protocol in both numerical simulation and on cloud-based IBM quantum processors, we demonstrate the successful separation and estimation of native noise spectrum components as well as SPAM error rates. We find that SPAM errors can significantly alter or mask important noise features, with spectra overestimated by up to 26.4% in a classical noise regime. Clear signatures of nonclassical noise are manifest in the reconstructed IBM-qubit dephasing spectra, once SPAM-error effects are compensated for. Our work provides a timely tool for benchmarking realistic sources of noise in qubit devices.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142185244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1103/physrevapplied.22.l021002
Shuanghai Wang, Kun He, Yongkang Xu, Zhuoyi Li, Jin Wang, Caitao Li, Xingze Dai, Jun Du, Yong-Lei Wang, Ronghua Liu, Xianyang Lu, Yongbing Xu, Liang He
In recent years, spin-orbit torque (SOT) generated by heavy metal (HM) has garnered increasing attention. However, SOT-magnetic random-access memory based on HM suffers from a low spin Hall angle and high current density. Here, we demonstrate that the critical switching-current density () in a multilayer structure of has been reduced by 79% compared with that of , achieving a value of 5.88 × . This value is considerably low among all reported values in the system literature. The reduction of is accompanied by enhanced dampinglike torque efficiency () and reduced coercive force (). A perfect linear correlation has been observed between and /, which supports the domain-wall depinning model of the SOT-induced magnetization reversal in this system. Crucially, this linearity extends to several metal dopants possessing the identical superlattice structure. This research offers insights into the future of low-power, high-density magnetic memory technology based on HM materials.
近年来，重金属（HM）产生的自旋轨道力矩（SOT）越来越受到关注。然而，基于重金属的 SOT 磁性随机存取存储器存在自旋霍尔角低和电流密度高的问题。在这里，我们证明了 Ta/(Pt/Ta)4/Pt/Co/Ta 多层结构中的临界开关电流密度 (Ic) 与 Ta/Pt/Co/Ta 相比降低了 79%，达到了 5.88 × 106A/cm2。在 Pt/Co 系统的所有文献报道值中，该值是相当低的。Ic 值的降低伴随着阻尼扭矩效率（βD）的提高和矫顽力（Hc）的降低。在 Ic 和 Hc/βD 之间观察到了完美的线性关系，这支持了该系统中 SOT 诱导磁化反转的畴壁衰减模型。最重要的是，这种线性关系延伸到具有相同超晶格结构的几种金属掺杂物。这项研究为未来基于 HM 材料的低功耗、高密度磁存储器技术提供了启示。
{"title":"Lower switching-current density in Ta/(Pt/X)n/Pt/Co/Ta (X = Ta,Mn,Cu,V,Zr, Bi; n = 3, 4) multilayers based on a domain-wall-depinning model","authors":"Shuanghai Wang, Kun He, Yongkang Xu, Zhuoyi Li, Jin Wang, Caitao Li, Xingze Dai, Jun Du, Yong-Lei Wang, Ronghua Liu, Xianyang Lu, Yongbing Xu, Liang He","doi":"10.1103/physrevapplied.22.l021002","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.l021002","url":null,"abstract":"In recent years, spin-orbit torque (SOT) generated by heavy metal (HM) has garnered increasing attention. However, SOT-magnetic random-access memory based on HM suffers from a low spin Hall angle and high current density. Here, we demonstrate that the critical switching-current density (<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>I</mi><mi>c</mi></msub></math>) in a multilayer structure of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Ta</mi><mo>/</mo><mo stretchy=\"false\">(</mo><mi>Pt</mi><mo>/</mo><mi>Ta</mi><msub><mo stretchy=\"false\">)</mo><mn>4</mn></msub><mo>/</mo><mi>Pt</mi><mo>/</mo><mi>Co</mi><mo>/</mo><mi>Ta</mi></math> has been reduced by 79% compared with that of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Ta</mi><mo>/</mo><mi>Pt</mi><mo>/</mo><mi>Co</mi><mo>/</mo><mi>Ta</mi></math>, achieving a value of 5.88 × <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msup><mn>10</mn><mn>6</mn></msup><mspace width=\"0.2em\"></mspace><mrow><mrow><mi mathvariant=\"normal\">A</mi></mrow></mrow><mo>/</mo><msup><mi>cm</mi><mn>2</mn></msup></math>. This value is considerably low among all reported values in the <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><mi>Pt</mi><mo>/</mo><mi>Co</mi></math> system literature. The reduction of <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>I</mi><mi>c</mi></msub></math> is accompanied by enhanced dampinglike torque efficiency (<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>β</mi><mi>D</mi></msub></math>) and reduced coercive force (<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mi>c</mi></msub></math>). A perfect linear correlation has been observed between <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>I</mi><mi>c</mi></msub></math> and <math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>H</mi><mi>c</mi></msub></math>/<math display=\"inline\" overflow=\"scroll\" xmlns=\"http://www.w3.org/1998/Math/MathML\"><msub><mi>β</mi><mi>D</mi></msub></math>, which supports the domain-wall depinning model of the SOT-induced magnetization reversal in this system. Crucially, this linearity extends to several metal dopants possessing the identical superlattice structure. This research offers insights into the future of low-power, high-density magnetic memory technology based on HM materials.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-28DOI: 10.1103/physrevapplied.22.024070
Chuanxin Zhang, Fei Dai, Xue Jiang, Dean Ta
Acoustic orbital angular momentum (OAM) beams hold potential for underwater communications, particle manipulation, and biomedical applications. However, adapting air-based OAM technologies to the underwater environment presents unique challenges. In the underwater environment, the medium cannot be considered acoustically soft, and commonly used ultrasound frequencies have shorter wavelengths compared with air, necessitating new design approaches. Conventional underwater ultrasonic lens design methods often rely on simplified models that neglect nonlocal interactions and diffraction within the structure, therefore leading to suboptimal performance. We introduce a novel nonlocal inverse design method by integrating the full-wave models with the nondominated sorting genetic algorithm II (NSGA-II). This approach diverges from conventional phase-based design by optimizing the physical structure of the lens to account for nonlocal interactions within the material. We experimentally demonstrate the performance when generating high-purity OAM beams underwater. Our experimental results show that this method can generate high-purity OAM beams underwater, achieving over 90% purity for the OAM beams of topological charges from m = 1 to m = 4. This is a significant improvement compared with traditional methods, which typically reach 70–89% purity. These findings highlight the practical applicability of our method for nonlocally designing the ultrasonic lens, paving the way for advancements in beam performance for various applications.
声轨道角动量（OAM）光束在水下通信、粒子操纵和生物医学应用方面具有潜力。然而，将基于空气的 OAM 技术应用于水下环境面临着独特的挑战。在水下环境中，介质不能被视为声学上的软介质，而且常用的超声波频率与空气相比波长较短，因此必须采用新的设计方法。传统的水下超声透镜设计方法往往依赖于简化模型，忽略了结构内部的非局部相互作用和衍射，因此导致性能不理想。我们通过将全波模型与非支配排序遗传算法 II（NSGA-II）相结合，引入了一种新的非局部反向设计方法。这种方法不同于传统的基于相位的设计，而是通过优化透镜的物理结构来考虑材料内部的非局部相互作用。我们通过实验证明了这种方法在水下产生高纯度 OAM 光束时的性能。实验结果表明，这种方法可以在水下生成高纯度的 OAM 光束，拓扑电荷从 m = 1 到 m = 4 的 OAM 光束纯度超过 90%。与传统方法相比，这是一个重大改进，传统方法的纯度通常为 70%-89%。这些发现凸显了我们非局部设计超声透镜方法的实用性，为提高各种应用的光束性能铺平了道路。
{"title":"Nonlocal inverse design of an ultrasonic lens for underwater manipulation of orbital angular momentum","authors":"Chuanxin Zhang, Fei Dai, Xue Jiang, Dean Ta","doi":"10.1103/physrevapplied.22.024070","DOIUrl":"https://doi.org/10.1103/physrevapplied.22.024070","url":null,"abstract":"Acoustic orbital angular momentum (OAM) beams hold potential for underwater communications, particle manipulation, and biomedical applications. However, adapting air-based OAM technologies to the underwater environment presents unique challenges. In the underwater environment, the medium cannot be considered acoustically soft, and commonly used ultrasound frequencies have shorter wavelengths compared with air, necessitating new design approaches. Conventional underwater ultrasonic lens design methods often rely on simplified models that neglect nonlocal interactions and diffraction within the structure, therefore leading to suboptimal performance. We introduce a novel nonlocal inverse design method by integrating the full-wave models with the nondominated sorting genetic algorithm II (NSGA-II). This approach diverges from conventional phase-based design by optimizing the physical structure of the lens to account for nonlocal interactions within the material. We experimentally demonstrate the performance when generating high-purity OAM beams underwater. Our experimental results show that this method can generate high-purity OAM beams underwater, achieving over 90% purity for the OAM beams of topological charges from <i>m</i> = 1 to <i>m</i> = 4. This is a significant improvement compared with traditional methods, which typically reach 70–89% purity. These findings highlight the practical applicability of our method for nonlocally designing the ultrasonic lens, paving the way for advancements in beam performance for various applications.","PeriodicalId":20109,"journal":{"name":"Physical Review Applied","volume":null,"pages":null},"PeriodicalIF":4.6,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142224165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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