| Li Yan
Nature, 30 June 2022, Volume 606 Issue 7916
《Nature》 June 30, 2022, Volume 606, Issue 7916
PhysicsPhysics
Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs
lithium iron arsenic Medium ordered and tunable Majorana zero-energy modes
▲ Author: Meng Li, Geng Li, Lu Cao, Xingtai Zhou, Xiancheng Wang et al.
▲ Link:
https://www.nature.com/articles /s41586-022-04744-8
▲ Abstract:
Here we report the formation of ordered and tunable majorola in naturally strained stoichiometric LiFeAs (lithium iron arsenic) via scanning tunneling microscopy /spectroscopy Nano zero energy mode. We observe biaxial charge density wave (CDW) stripes along the iron-iron and arsenic-arsenic directions in the strained region. The vortices are fixed on the CDW stripes in the arsenic-arsenic direction, forming an ordered vortex array.
We found that more than 90% of the vortices are topological and have the characteristics of Majorana zero-energy modes at the vortex center, forming an ordered Majorana zero-energy mode array with a density similar to geometry Shape can be adjusted by external magnetic fields. It is worth noting that as the distance between adjacent vortices decreases, the multi-end dipoles begin to couple to each other.
Our discovery provides an ordered and controllable Majorana zero-energy mode array, providing an important high-quality research platform for realizing topological quantum computing .
▲ Abstract：
Here we report the formation of an ordered and tunable MZM lattice in naturally strained stoichiometric LiFeAs by scanning tunneling microscopy/spectroscopy. We observe biaxial charge density wave (CDW) stripes along the Fe–Fe and As–As directions in the strained regions. The vortices are pinned on the CDW stripes in the As–As direction and form an ordered lattice. We detect that more than 90 percent of the vortices are topological and possess the characteristics of isolated MZMs at the vortex centre, forming an ordered MZM lattice with the density and the geometry tunable by an external magnetic field. Notably, with decreasing the spacing of neighboring vortices, the MZMs start to couple with each other. Our findings provide a pathway towards tunable and ordered MZM lattices as a platform for future topological quantum computation.
Axial Higgs mode detected by quantum pathway interference in RTe3
Axial Higgs mode detected in RTe3
▲ Author: Yiping Wang, Ioannis Petrides, Grant McNamara et al .
▲ Link:
https ://www.nature.com/articles/s41586-022-04746-6
▲ Abstract:
Here we discover an axial Higger in the charge density wave (CDW) system RTe3 using quantum path interference Smo. In RTe3 (R = La, Gd), the electron ordered even bands have equal angular momentum or different angular momentum.
Therefore, the Raman scattering tensor associated with the Higgs mode contains symmetric and antisymmetric components, which are excited by two different but degenerate pathways. This results in constructive or destructive interference of paths depending on the polarization choice of the incident light and the Raman scattered light. The qualitative behavior of the Raman spectroscopy is captured by an appropriate tight-binding model including the axial Higgs mode.
The elucidation of the antisymmetric component is direct evidence that the Higgs mode contains an axial vector representation (i.e., pseudoangular momentum) and implies that charge density waves are unconventional.We therefore provide a method to measure the quantum properties of collective moduli without resorting to extreme experimental conditions.
▲ Abstract：
Here we discover an axial Higgs mode in the CDW system RTe3 using the interference of quantum pathways. In RTe3 (R = La, Gd), the electronic ordering couples bands of equal or different angular momenta. As such, the Raman scattering tensor associated with the Higgs mode contains both symmetric and antisymmetric components, which are excited via two distinct but degenerate pathways. This leads to constructive or destructive interference of these pathways, depending on the choice of the incident and Raman-scattered light polarization. Qualitative behavior of the Raman spectra is well captured by an appropriate tight-binding model, including an axial Higgs mode. Elucidation of the antisymmetric component is direct evidence that the Higgs mode contains an axial vector representation (that is, a pseudo-angular momentum) and hints that the CDW is unconventional. Thus, we provide a means for measuring quantum properties of collective modes without resorting to extreme experimental conditions.
Fault-tolerant operation of a logical qubit in a diamond quantum processor Fault-tolerant operation of
▲ Author: M. H. Abobeih, Y. Wang, J. Randall, S. J. H. Loenen et al.
▲ Link:
https://www.nature.com/articles/s41586-022-048 19-6
▲ Summary:
Here we demonstrate fault-tolerant operation on logical qubits using spin qubits in a diamond quantum processor. Our approach is based on 5 qubits and a newly discovered protocol that can achieve fault tolerance using 7 qubits.
We encode logical qubits using a new protocol based on repeated multi-qubit measurements and show that it outperforms non-fault-tolerant encoding schemes. We then perform fault-tolerant operation of logic qubits through a complete set of single-qubit Clifford gates.
Finally, we demonstrate real-time processing of marker stabilizer measurements. Such measurements are the basis for error-tolerant quantum error correction. Although future improvements in fidelity and qubit number will be required to suppress logical error rates below physical error rates, our implementation of a fault-tolerant protocol at the logical qubit level is a step toward solid-state spin-based quantum information processing A crucial step.
▲ Abstract：
Here, we demonstrate fault-tolerant operations on a logical qubit using spin qubits in diamond. Our approach is based on the five-qubit code with a recently discovered flag protocol that enables fault tolerance using a total of seven qubits. We encode the logical qubit using a new protocol based on repeated multi-qubit measurements and show that it outperforms non-fault-tolerant encoding schemes. We then fault-tolerantly manipulate the logical qubit through a complete set of single-qubit Clifford gates. Finally, we demonstrate flagged stabilizer measurements with real-time processing of the outcomes. Such measurements are a primitive for fault-tolerant quantum error correction. Although future improvements in fidelity and the number of qubits will be required to suppress logical error rates below the physical error rates , our realization of fault-tolerant protocols on the logical-qubit level is a key step towards quantum information processing based on solid-state spins.
Material ScienceMaterial Science
Chiral molecular intercalation superlattices
Chiral molecular intercalation superlattice materials
▲ Author: Qi Qian, Huaying Ren, Jingyuan Zhou, Zhong Wan, Jingxuan Zhou et al.
▲ Link:
https://www.nature.com/articles/s41586-022-04846-3
▲ Abstract:
Here we report a A new type of chiral molecular intercalated superlattice material (CMIS), which can serve as a powerful solid-state chiral material platform to explore chirality-induced spin selectivity (CISS). CMIS is prepared by intercalating two-dimensional layered crystals (2DACs) (such as TaS2 and TiS2) and selected chiral molecules (such as R-α-methylbenzylamine and S-α-methylbenzylamine).
X-ray diffraction and transmission electron microscopy studies show that the superlattice structure has alternating crystal atomic layers and self-assembled chiral molecular layers. Circular dichroism studies show clear chirality-dependent signals between right-handed and left-handed CMIS.
In addition, by using the obtained CMIS as a spin filter layer, we constructed a spin tunneling electronic device with obvious chirality dependence, achieving a spin magnetoresistive ratio of more than 300% and a spin polarity of more than 60%. conversion rate.
▲ Abstract：
Here we report a new class of chiral molecular intercalation superlattices (CMIS) as a robust solid-state chiral material platform for exploring CISS. The CMIS were prepared by intercalating layered two-dimensional atomic crystals (2DACs) (such as TaS2 and TiS2) with selected chiral molecules (such as R-α-methylbenzylamine and S-α-methylbenzylamine). The X-ray diffraction and transmission electron microscopy studies demonstrate highly ordered superlattice structures with alternating crystalline atomic layers and self-assembled chiral molecular layers . Circular dichroism studies show clear chirality-dependent signals between right-handed (R-) and left-handed (S-) CMIS. Furthermore, by using the resulting CMIS as the spin-filtering layer, we create spin-selective tunnelling junctions with a distinct chirality-dependent tunnelling current, achieving a tunnelling magnetoresistance ratio of more than 300 per cent and a spin polarization ratio of more than 60 per cent.
Hypocrystalline ceramic aerogels for thermal insulation at extreme conditions
Hypocrystalline ceramic aerogels for thermal insulation at extreme conditions
Ceramic airgel
▲ Author: Jingran Guo, Shubin Fu, Yuanpeng Deng, Xiang Xu et al.
▲ Link:
https://www.nature.com/articles/s41586-022-04784-0
▲ Summary:
in Here, we report a zigzag-structured subcrystalline zircon nanofiber aerogel with exceptional thermomechanical stability and ultralow thermal conductivity at high temperatures.
airgel has a near-zero Poisson’s ratio (3.3 × 10−4) and a near-zero thermal expansion coefficient (1.2 × 10−7/°C), which ensures excellent structural flexibility and thermal Mechanical behavior. They demonstrate extremely low strength degradation (less than 1%) and extremely high thermal stability under severe thermal shock and high operating temperatures (up to 1300 degrees Celsius).
By wrapping residual carbon species in subcrystalline zircon fibers, we significantly reduced thermal radiation heat transfer and achieved one of the lowest high-temperature thermal conductivity coefficients in ceramic aerogels to date, 104 mW at 1000 degrees Celsius. m-1 K -1. The combination of thermomechanical and thermal insulating properties provides an attractive material system for robust insulation in extreme conditions.
▲ Abstract：
Here we report a multiscale design of hypocrystalline zircon nanofibrous aerogels with a zig-zag architecture that leads to exceptional thermomechanical stability and ultralow thermal conductivity at high temperatures. The aerogels show a near-zero Poisson's ratio (3.3 × 10 −4) and a near-zero thermal expansion coefficient (1.2 × 10−7 per degree Celsius), which ensures excellent structural flexibility and thermomechanical properties. They show high thermal stability with ultralow strength degradation (less than 1 per cent) after sharp thermal shocks, and a high working temperature (up to 1,300 degrees Celsius). By deliberately entrapping residue carbon species in the constituent hypocrystalline zircon fibers, we substantially reduce the thermal radiation heat transfer and achieve one of the lowest high-temperature thermal conductivities among ceramic aerogels so far—104 milliwatts per meter per kelvin at 1,000 degrees Celsius. The combined thermomechanical and thermal insulating properties offer an attractive material system for robust thermal insulation under extreme conditions. 0 dynamic weakening fault Intermittent laboratory earthquakes in mud
▲ Author: V. Rubino, N. Lapusta & A. J. Rosakis
▲ Link:
https://www.nature.com/articles/s41586-022-04749-3
▲ Summary:
is here , through laboratory experiments, we show that spontaneously propagating dynamic ruptures navigate fault zones with fine rock fault gouge through complex, intermittent slip processes and violent frictional evolution. This includes repeated cessation of rupture propagation caused by friction intensification at lower slip rates, and dynamic seismic re-nucleation caused by significantly rapid weakening of friction at higher slip rates consistent with flash heating.
The spontaneous repeated weakening and strengthening of friction in fine rock fault gouge highlights the fundamental dependence of friction on slip rate and related processes, such as shear heating, localization and delocalization of shear, and expansion and expansion of shear layers. Compaction. Our findings extend experimental support for the concept that coseismic weakening may allow earthquake ruptures to breach stable fault zones, which has important implications for studying seismic hazards.
▲ Abstract：
Here, using lab experiments, we show that spontaneously propagating dynamic ruptures navigate a fault region with fine rock gouge through complex, intermittent slip processes with dramatic friction evolution. These include repeated arrest of rupture propagation caused by friction strengthening at lower slip rates and dynamic earthquake re-nucleation enabled by pronounced rapid friction weakening at higher slip rates consistent with flash heating. The spontaneous repeated weakening and strengthening of friction in fine rock gouge highlights the fundamental dependence of friction on slip rate and associated processes, such as shear heating, localization and delocalization of shear, and dilation and compaction of the shear layer. Our findings expand experimental support of the concept that co-seismic weakening may enable earthquake rupture to break through stable fault regions, with substantial implications for seismic hazard.
