22 results on '"Zhen Bi"'
Search Results
2. Birefringence-like spin transport via linearly polarized antiferromagnetic magnons
- Author
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Jiahao Han, Ran Cheng, Zhen Bi, Liang Fu, Luqiao Liu, Junxiang Xiang, Pengxiang Zhang, Yabin Fan, Taqiyyah S. Safi, and Joseph Finley
- Subjects
Physics ,Angular momentum ,Condensed matter physics ,Spins ,Spintronics ,Magnon ,Demagnetizing field ,Biomedical Engineering ,Bioengineering ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Magnetic field ,Antiferromagnetism ,Condensed Matter::Strongly Correlated Electrons ,General Materials Science ,Electrical and Electronic Engineering ,0210 nano-technology ,Spin-½ - Abstract
Antiferromagnets (AFMs) possess great potential in spintronics because of their immunity to external magnetic disturbance, the absence of a stray field or the resonance in the terahertz range1,2. The coupling of insulating AFMs to spin–orbit materials3–7 enables spin transport via AFM magnons. In particular, spin transmission over several micrometres occurs in some AFMs with easy-axis anisotropy8,9. Easy-plane AFMs with two orthogonal, linearly polarized magnon eigenmodes own unique advantages for low-energy control of ultrafast magnetic dynamics2. However, it is commonly conceived that these magnon modes are less likely to transmit spins because of their vanishing angular momentum9–11. Here we report experimental evidence that an easy-plane insulating AFM, an α-Fe2O3 thin film, can efficiently transmit spins over micrometre distances. The spin decay length shows an unconventional temperature dependence that cannot be captured considering solely thermal magnon scatterings. We interpret our observations in terms of an interference of two linearly polarized, propagating magnons in analogy to the birefringence effect in optics. Furthermore, our devices can realize a bi-stable spin-current switch with a 100% on/off ratio under zero remnant magnetic field. These findings provide additional tools for non-volatile, low-field control of spin transport in AFM systems. Easy-plane antiferromagnet materials promise low-energy control of ultrafast magnetic dynamics in future spintronics applications, but host magnons with vanishing angular momentum, which makes spin transport via magnons unlikely. Through interference of two linearly polarized propagating magnons, spin transport over micrometre distances is yet possible.
- Published
- 2020
3. Mechanistic influence on uniformity of sheet resistance of AlGaN/GaN HEMT grown on Si substrate with the graded AlGaN buffer layers
- Author
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Jinbang Ma, Yachao Zhang, Yifan Li, Tao Zhang, Yixin Yao, Qian Feng, Zhen Bi, Jincheng Zhang, and Yue Hao
- Subjects
Condensed Matter Physics ,Instrumentation ,Surfaces, Coatings and Films - Published
- 2022
4. Investigation on the relationship between dislocation type and the annihilation mechanism of GaN-on-Si
- Author
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Jinbang Ma, Yachao Zhang, Yifan Li, Yixin Yao, Tao Zhang, Qian Feng, Zhen Bi, Lansheng Feng, Jincheng Zhang, and Yue Hao
- Subjects
Mechanics of Materials ,Mechanical Engineering ,General Materials Science ,Condensed Matter Physics - Published
- 2022
5. Unconventional ferroelectricity in moiré heterostructures
- Author
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Takashi Taniguchi, Qiong Ma, William A. Tisdale, Nuh Gedik, Zhen Bi, Jing Kong, Raymond Ashoori, Sergio C. de la Barrera, Yang Zhang, Ming-Hao Liu, Pablo Jarillo-Herrero, Kenji Watanabe, Nannan Mao, Zhiren Zheng, Natasha Kiper, Su-Yang Xu, and Liang Fu
- Subjects
Multidisciplinary ,Materials science ,Condensed matter physics ,Graphene ,Superlattice ,Heterojunction ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Polarization (waves) ,01 natural sciences ,Ferroelectricity ,law.invention ,chemistry.chemical_compound ,chemistry ,Boron nitride ,law ,0103 physical sciences ,Displacement field ,010306 general physics ,0210 nano-technology ,Bilayer graphene - Abstract
The constituent particles of matter can arrange themselves in various ways, giving rise to emergent phenomena that can be surprisingly rich and often cannot be understood by studying only the individual constituents. Discovering and understanding the emergence of such phenomena in quantum materials-especially those in which multiple degrees of freedom or energy scales are delicately balanced-is of fundamental interest to condensed-matter research1,2. Here we report on the surprising observation of emergent ferroelectricity in graphene-based moire heterostructures. Ferroelectric materials show electrically switchable electric dipoles, which are usually formed by spatial separation between the average centres of positive and negative charge within the unit cell. On this basis, it is difficult to imagine graphene-a material composed of only carbon atoms-exhibiting ferroelectricity3. However, in this work we realize switchable ferroelectricity in Bernal-stacked bilayer graphene sandwiched between two hexagonal boron nitride layers. By introducing a moire superlattice potential (via aligning bilayer graphene with the top and/or bottom boron nitride crystals), we observe prominent and robust hysteretic behaviour of the graphene resistance with an externally applied out-of-plane displacement field. Our systematic transport measurements reveal a rich and striking response as a function of displacement field and electron filling, and beyond the framework of conventional ferroelectrics. We further directly probe the ferroelectric polarization through a non-local monolayer graphene sensor. Our results suggest an unconventional, odd-parity electronic ordering in the bilayer graphene/boron nitride moire system. This emergent moire ferroelectricity may enable ultrafast, programmable and atomically thin carbon-based memory devices.
- Published
- 2020
6. Emergent fractons and algebraic quantum liquid from plaquette melting transitions
- Author
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Zhen Bi, Yizhi You, and Michael Pretko
- Subjects
High Energy Physics - Theory ,Physics ,Valence (chemistry) ,Condensed Matter - Mesoscale and Nanoscale Physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Condensed matter physics ,High Energy Physics::Lattice ,FOS: Physical sciences ,Quantum number ,Topological defect ,Condensed Matter - Strongly Correlated Electrons ,High Energy Physics - Theory (hep-th) ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Solid phases ,Condensed Matter::Strongly Correlated Electrons ,Algebraic number ,Quantum ,Fracton - Abstract
Paramagnetic spin systems with spontaneously broken spatial symmetries, such as valence bond solid (VBS) phases, can host topological defects carrying non-trivial quantum numbers, which enables the paradigm of deconfined quantum criticality. In this work, we study the properties of topological defects in valence plaquette solid (VPS) phases on square and cubic lattices. We show that the defects of the VPS order parameter, in addition to possessing non-trivial quantum numbers, have fracton mobility constraints deep in the VPS phase, which has been overlooked previously. The spinon inside a single vortex cannot move freely in any direction, while a dipolar pair of vortices with spinon pairs can only move perpendicular to its dipole moment. These mobility constraints, while they persist, can potentially inhibit the condensation of vortices and preclude a continuous transition from the VPS to the N\'eel antiferromagnet. Instead, the VPS melting transition can be driven by proliferation of spinon dipoles. For example, we argue that a $2d$ VPS can melt into a stable gapless phase in the form of an algebraic bond liquid with algebraic correlations and long range entanglement. Such a bond liquid phase yields a concrete example of the elusive $2d$ Bose metal with symmetry fractionalization. We also study $3d$ valence plaquette and valence cube ordered phase, and demonstrate that the topological defects therein also have fractonic dynamics. Possible nearby phases after melting the valence plaquettes or cubes are also discussed.
- Published
- 2020
7. Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide
- Author
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Zhen Bi and Liang Fu
- Subjects
Electronic properties and materials ,Field (physics) ,Exciton ,Science ,Van Hove singularity ,FOS: Physical sciences ,General Physics and Astronomy ,02 engineering and technology ,Two-dimensional materials ,01 natural sciences ,General Biochemistry, Genetics and Molecular Biology ,Article ,Density wave theory ,symbols.namesake ,Condensed Matter - Strongly Correlated Electrons ,Electric field ,0103 physical sciences ,010306 general physics ,Physics ,Condensed Matter::Quantum Gases ,Condensed Matter - Materials Science ,Multidisciplinary ,Strongly Correlated Electrons (cond-mat.str-el) ,Spintronics ,Condensed matter physics ,Condensed Matter::Other ,Fermi level ,Materials Science (cond-mat.mtrl-sci) ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,Magnetic field ,symbols ,Condensed Matter::Strongly Correlated Electrons ,0210 nano-technology - Abstract
Artificial moir\'e superlattices in 2d van der Waals heterostructure is a new venue for realizing and controlling correlated electronic phenomena. Recently, twisted bilayer WSe$_2$ emerged as a new robust moir\'e system hosting a correlated insulator at moir\'e half-filling over a range of twist angle. In this work, we present a theory of this insulating state as an excitonic density wave due to intervalley electron-hole pairing. We show that exciton condensation is strongly enhanced by a van Hove singularity near the Fermi level. Our theory explains the remarkable sensitivity of the insulating gap to the vertical electric field. In contrast, the gap is weakly reduced by a perpendicular magnetic field, with quadratic dependence at low field. The different responses to electric and magnetic field can be understood in terms of pair-breaking versus non-pair-breaking effects in a BCS analog of the system. We further predict superfluid spin transport in this electrical insulator, which can be detected by optical spin injection and spatial-temporal imaging., Comment: 10 pages, 8 figures. To appear in Nature Communications
- Published
- 2019
8. Effects of the pretreatment of Si substrate before the pre-deposition of Al on GaN-on-Si
- Author
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Yachao Zhang, Yifan Li, Zhen Bi, Jincheng Zhang, Yue Hao, Jinbang Ma, Tao Zhang, Yixin Yao, and Qian Feng
- Subjects
Work (thermodynamics) ,Materials science ,Morphology (linguistics) ,Photoluminescence ,business.industry ,Surface finish ,Condensed Matter Physics ,Root mean square ,Full width at half maximum ,Quality (physics) ,Si substrate ,Optoelectronics ,General Materials Science ,Electrical and Electronic Engineering ,business - Abstract
In this work, we report a method that the Si substrate is pre-treated in the atmosphere of high temperature AlN before the depositon of Al to improve the quality of GaN-on-Si, which is studied by few people. Compared to the untreated sample, the pre-treated one exhibits smoother surface morphology with a root mean square roughness (RMS) value of 0.580 nm and the full width at half maximum (FWHM) of GaN (102) plane also decreases from 1484 arcsec to 1303 arcsec. Moreover, we give an explanation for the extra shoulder peaks in the photoluminescence (PL) spectrum. This enhancement of quality and surface morphology of GaN can be attributed to the improvement of surface flatness of Si substrate, which contributes to the conversion of AlN to two-dimensional growth mode, leading to a smoother surface of GaN. And the reason for the improvement of Si substrate is also investigated in this work.
- Published
- 2021
9. Superconductivity near a Ferroelectric Quantum Critical Point in Ultralow-Density Dirac Materials
- Author
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Jonathan Ruhman, Zhen Bi, and Vladyslav Kozii
- Subjects
Superconductivity ,Physics ,Quantum Physics ,cond-mat.supr-con ,Condensed matter physics ,Phonon ,Condensed Matter - Superconductivity ,QC1-999 ,FOS: Physical sciences ,General Physics and Astronomy ,Fermi energy ,Electron ,Renormalization group ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Superconductivity (cond-mat.supr-con) ,Critical point (thermodynamics) ,Quantum critical point ,Condensed Matter::Superconductivity ,0103 physical sciences ,Coulomb ,010306 general physics ,Astronomical and Space Sciences - Abstract
Author(s): Kozii, V; Bi, Z; Ruhman, J | Abstract: The experimental observation of superconductivity in doped semimetals and semiconductors, where the Fermi energy is comparable to or smaller than the characteristic phonon frequencies, is not captured by the conventional theory. In this paper, we propose a mechanism for superconductivity in ultralow-density three-dimensional Dirac materials based on the proximity to a ferroelectric quantum critical point. We derive a low-energy theory that takes into account both the strong Coulomb interaction and the direct coupling between the electrons and the soft phonon modes. We show that the Coulomb repulsion is strongly screened by the lattice polarization near the critical point even in the case of a vanishing carrier density. Using a renormalization group analysis, we demonstrate that the effective electron-electron interaction is dominantly mediated by the transverse phonon mode. We find that the system generically flows towards strong electron-phonon coupling. Hence, we propose a new mechanism to simultaneously produce an attractive interaction and suppress strong Coulomb repulsion, which does not require retardation. For comparison, we perform the same analysis for covalent crystals, where lattice polarization is negligible. We obtain qualitatively similar results, though the screening of the Coulomb repulsion is much weaker. We then apply our results to study superconductivity in the low-density limit. We find a strong enhancement of the transition temperature upon approaching the quantum critical point. Finally, we also discuss scenarios to realize a topological p-wave superconducting state in covalent crystals close to the critical point.
- Published
- 2019
10. Designing Flat Band by Strain
- Author
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Liang Fu, Zhen Bi, and Noah F. Q. Yuan
- Subjects
Condensed Matter - Materials Science ,Magic angle ,Materials science ,Strain (chemistry) ,Condensed matter physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Bilayer ,Scanning tunneling spectroscopy ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter::Mesoscopic Systems and Quantum Hall Effect ,01 natural sciences ,Condensed Matter - Strongly Correlated Electrons ,Transition metal ,0103 physical sciences ,010306 general physics ,0210 nano-technology ,Bilayer graphene ,Electronic properties - Abstract
We study the effects of heterostrain on moir\'e bands in twisted bilayer graphene and bilayer transition metal dichalcogenide (TMD) systems. For bilayer graphene with twist angle near $1^\circ$, we show that heterostrain significantly increases the energy separation between conduction and valence bands as well as the Dirac velocity at charge neutrality, which resolves several puzzles in scanning tunneling spectroscopy and quantum oscillation experiments at once. For bilayer TMD, we show that applying small heterostrain generally leads to flat moir\'e bands that are highly tunable., Comment: 10 pages, 11 figures
- Published
- 2019
11. A model for continuous thermal Metal to Insulator Transition
- Author
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Zhen Bi, Cenke Xu, and Chao-Ming Jian
- Subjects
High Energy Physics - Theory ,Quantum phase transition ,Physics ,Condensed matter physics ,Strongly Correlated Electrons (cond-mat.str-el) ,FOS: Physical sciences ,Insulator (electricity) ,01 natural sciences ,7. Clean energy ,Fick's laws of diffusion ,010305 fluids & plasmas ,Metal ,Condensed Matter - Strongly Correlated Electrons ,High Energy Physics - Theory (hep-th) ,visual_art ,Quantum critical point ,0103 physical sciences ,Thermal ,visual_art.visual_art_medium ,Condensed Matter::Strongly Correlated Electrons ,Symmetry breaking ,010306 general physics ,Majorana fermion - Abstract
We propose a $d-$dimensional interacting Majorana fermion model with quenched disorder, which gives us a continuous quantum phase transition between a diffusive thermal metal phase with a finite entropy density to an insulator phase with zero entropy density. This model is based on coupled Sachdev-Ye-Kitaev model clusters, and hence has a controlled large-$N$ limit. The metal-insulator transition is accompanied by a spontaneous time-reversal symmetry breaking. We perform controlled calculations to show that the diffusion constant jumps to zero discontinuously at the metal-insulator transition, while the time-reversal symmetry breaking order parameter increases continuously., Comment: 11 pages
- Published
- 2017
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12. Morphology control of ultrafine cuprous oxide powder and its growth mechanism
- Author
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Kang-gen Zhou, Zhen Bi, Yue-jun Wang, and Yan Cao
- Subjects
Supersaturation ,Morphology (linguistics) ,Inorganic chemistry ,Metals and Alloys ,Nucleation ,Oxide ,Geotechnical Engineering and Engineering Geology ,Condensed Matter Physics ,Morphology control ,Crystal ,Truncated octahedron ,chemistry.chemical_compound ,chemistry ,Octahedron ,Materials Chemistry - Abstract
Four shapes of Cu2O particles as sphere, cube, truncated octahedron and octahedron were prepared via glucose reduction of Cu(II) under alkaline condition. The products were characterized by XRD and SEM. The effects of the precursor (CuO, Cu(OH)2), reaction temperature and glucose concentration on morphology of Cu2O particles were investigated, and the mechanism of morphology control was discussed on the basic theory of crystal nucleation and growth. It is found that the Cu+ supersaturation is remarkably influenced by the precursor kind, reaction temperature and glucose concentration, and the morphology of Cu2O particles can be controlled by the Cu+ supersaturation.
- Published
- 2010
13. A Back-Illuminated Vertical-Structure Ultraviolet Photodetector Based on an RF-Sputtered ZnO Film
- Author
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Zhen Bi, Xiaodong Yang, Dong Wang, Jingwen Zhang, Xun Hou, Xuming Bian, and Xin’an Zhang
- Subjects
Photocurrent ,Materials science ,business.industry ,Photoconductivity ,Photodetector ,Sputter deposition ,Condensed Matter Physics ,medicine.disease_cause ,Electronic, Optical and Magnetic Materials ,Responsivity ,Optics ,Materials Chemistry ,medicine ,Optoelectronics ,Electrical and Electronic Engineering ,Thin film ,business ,Ultraviolet ,Dark current - Abstract
A back-illuminated vertical-structure ZnO ultraviolet (UV) detector was fabricated using an indium-tin oxide (ITO) electrode. Ordered ITO and ZnO films were grown on a quartz substrate by radiofrequency sputtering. At 5 V bias, the dark current was 640 μA and the photocurrent was 16.8 mA under UV illumination (365 nm, 10 μW), indicating a high responsivity of 1616 A/W. The response time measurements showed a rise time of 71.2 ns and a decay time of 377 μs. The ZnO detector performed well and can be used in a focal-plane array for UV image detection.
- Published
- 2008
14. A High-Performance Ultraviolet Photoconductive Detector Based on a ZnO Film Grown by RF Sputtering
- Author
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Dong Wang, Xun Hou, Jingwen Zhang, Xuming Bian, Xin’an Zhang, Zhen Bi, and Weifeng zhang
- Subjects
Materials science ,Annealing (metallurgy) ,business.industry ,Photodetector ,Condensed Matter Physics ,medicine.disease_cause ,Electronic, Optical and Magnetic Materials ,Responsivity ,Optics ,Sputtering ,Physical vapor deposition ,Rise time ,Materials Chemistry ,medicine ,Optoelectronics ,Electrical and Electronic Engineering ,Thin film ,business ,Ultraviolet - Abstract
A high-performance metal-semiconductor-metal (MSM) ultraviolet photodetector was fabricated based on a ZnO film with Al interdigitated (IDT) electrodes. A c-axis-oriented ZnO film was grown on a SiO2/Si (100) substrate at room temperature by a reactive radiofrequency (RF) sputtering technique and then annealed at 900°C in pure O2 ambient for 1 h. The fabricated ZnO ultraviolet (UV) detector demonstrated a high responsivity of 2069 A/W when biased at 5 V, which could be attributed to the influence of the annealing process in pure O2 ambient. The response time measurement showed a rise time (10–90%) of 45.1 ns and a decay time (1 − 1/e) of 541 μs.
- Published
- 2007
15. Classification and description of bosonic symmetry protected topological phases with semiclassical nonlinear sigma models
- Author
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Zhen Bi, Alex Rasmussen, Cenke Xu, and Kevin Slagle
- Subjects
Physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Sigma model ,Group cohomology ,FOS: Physical sciences ,Sigma ,Semiclassical physics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Condensed Matter Physics ,Topology ,Cohomology ,Electronic, Optical and Magnetic Materials ,Condensed Matter - Strongly Correlated Electrons ,Nonlinear system ,Lattice (order) ,Homogeneous space - Abstract
In this paper we systematically classify and describe bosonic symmetry protected topological (SPT) phases in all physical spatial dimensions using semiclassical nonlinear Sigma model (NLSM) field theories. All the SPT phases on a $d-$dimensional lattice discussed in this paper can be described by the same NLSM, which is an O(d+2) NLSM in $(d+1)-$dimensional space-time, with a topological $\Theta-$term. The field in the NLSM is a semiclassical Landau order parameter with a unit length constraint. The classification of SPT phases discussed in this paper based on their NLSMs is consistent with the more mathematical classification based on group cohomology. Besides the classification, the formalism used in this paper also allows us to explicitly discuss the physics at the boundary of the SPT phases, and it reveals the relation between SPT phases with different symmetries. For example, it gives many of these SPT states a natural "decorated defect" construction., Comment: 16 pages
- Published
- 2015
16. Construction and Field Theory of Bosonic Symmetry Protected Topological states beyond Group Cohomology
- Author
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Zhen Bi and Cenke Xu
- Subjects
Physics ,Strongly Correlated Electrons (cond-mat.str-el) ,Group cohomology ,FOS: Physical sciences ,Condensed Matter Physics ,Topology ,Symmetry protected topological order ,Electronic, Optical and Magnetic Materials ,Topological defect ,Condensed Matter - Strongly Correlated Electrons ,Effective field theory ,Order (group theory) ,Equivariant cohomology ,Field theory (psychology) ,Symmetry (geometry) - Abstract
We construct a series of bosonic symmetry protected topological (BSPT) states beyond group cohomology classification using "decorated defects" approach. This construction is based on topological defects of ordinary Landau order parameters, decorated with the bosonic short range entangled (BSRE) states in $(4k+3)d$ and $(4k+5)d$ space-time (with $k$ being nonnegative integers), which do not need any symmetry. This approach not only gives these BSPT states an intuitive physical picture, it also allows us to derive the effective field theory for all these BSPT states beyond group cohomology., 7 pages
- Published
- 2015
17. Glancing-incidence X-ray analysis of ZnO thin films and ZnO/ZnMgO heterostructures grown by laser-MBE
- Author
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Weifeng zhang, Q.Y. Xu, Jingwen Zhang, Yongning He, Wang Hong-bo, Zhen Bi, Xun Hou, and Xiaodong Yang
- Subjects
Photoluminescence ,Materials science ,Analytical chemistry ,Heterojunction ,Surface finish ,Condensed Matter Physics ,Laser ,law.invention ,Inorganic Chemistry ,X-ray reflectivity ,law ,Materials Chemistry ,Thin film ,Layer (electronics) ,Molecular beam epitaxy - Abstract
In this paper, we report on glancing-incidence X-ray analysis (GIXA) of ZnO thin films, ZnO/ZnMgO and ZnO/Au heterostructures grown by laser molecular beam epitaxy (L-MBE) on c-plane Al2O3 substrates. The surface and interface sensitivity of X-ray reflectivity (XRR) has been exploited to evaluate the surfaces and interfaces of ZnO-based structures. The presence of smooth interfaces is responsible for the observation of intensity oscillation in XRR, which is well correlated to the clear Pendellosung fringes in high-resolution X-ray diffraction (HRXRD) measurements. In addition, the simulation of XRR data yields reliable and precise information of the layer thickness, the surface and interface roughness of each layer. The correlation of a smooth surface and high optical and structural quality is substantiated by time-integrated photoluminescence (TIPL) and XRD measurements of ZnO/ZnMgO heterostructure and ZnO thin films. The intense exciton-related emission, in contrast to a negligible deep-level radiation and the high c-axis orientation of ZnO films, indicates good optical and structural properties due to the superior surface and interface quality of our samples. (c) 2005 Elsevier B.V. All rights reserved.
- Published
- 2005
18. Anyon and loop braiding statistics in field theories with a topologicalΘterm
- Author
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Yi-Zhuang You, Zhen Bi, and Cenke Xu
- Subjects
Physics ,Sigma model ,Anyon ,Semiclassical physics ,Condensed Matter Physics ,Topology ,01 natural sciences ,Topological quantum computer ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,Condensed Matter - Strongly Correlated Electrons ,Phase factor ,Nonlinear system ,Formalism (philosophy of mathematics) ,0103 physical sciences ,Statistics ,010306 general physics - Abstract
We demonstrate that the anyon statistics and three-loop statistics of various 2d and 3d topological phases can be derived using semiclassical nonlinear Sigma model field theories with a topological $\Theta$-term. In our formalism, the braiding statistics has a natural geometric meaning: The braiding process of anyons or loops leads to a nontrivial field configuration in the space-time, which will contribute a braiding phase factor due to the $\Theta$-term., Comment: 4 pages, 3 figures
- Published
- 2014
19. Line defects in three-dimensional symmetry-protected topological phases
- Author
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Zhen Bi, Cenke Xu, and Alex Rasmussen
- Subjects
Physics ,Line defects ,Condensed Matter - Strongly Correlated Electrons ,Theoretical physics ,Strongly Correlated Electrons (cond-mat.str-el) ,0103 physical sciences ,FOS: Physical sciences ,Symmetry (geometry) ,010306 general physics ,Condensed Matter Physics ,01 natural sciences ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials - Abstract
A 3d symmetry protected topological phase, by definition must have symmetry protected nontrivial boundary states, namely its 2d boundary must be either gapless or degenerate. In this work we demonstrate that once we couple a 3d SPT phase to a lattice dynamical Z2 gauge field, in many cases the Z2 vison loop excitation (line defect) can be viewed as a "1d boundary" of the 3d SPT phase, and this line defect is guaranteed to have gapless or degenerate spectrum, which is also protected by the symmetry of the SPT phase., Comment: 5 pages, 2 figures
- Published
- 2014
20. Fabrication and optical properties of spear-like ZnO nanostructures by chemical vapor deposition
- Author
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Ya'nan Hu, Zhen Bi, Xin’an Zhang, Xuming Bian, Xun Hou, Dong Wang, Gaoming Li, and Jingwen Zhang
- Subjects
Materials science ,Nanostructure ,Photoluminescence ,Mechanical Engineering ,Analytical chemistry ,Chemical vapor deposition ,Condensed Matter Physics ,Nanomaterials ,Field emission microscopy ,Mechanics of Materials ,General Materials Science ,Emission spectrum ,Luminescence ,Powder diffraction - Abstract
Novel spear-like ZnO nanowires with a length of 2 μm and a width of 0.26 μm were synthesized on p-Si (100) substrates by chemical vapor deposition (CVD) method without catalysts. The crystal structures and morphographies of the products were characterized by X-ray powder diffraction (XRD) and high resolution field emission scanning electron microscope (FE-SEM). Energy dispersive X-ray spectrum (EDS) demonstrated that the spear-like microstuctures consist of element Zn and O. It indicated that the shapes of the products strongly depend on the growth conditions. The optical properties of spear-like ZnO nanostructures were investigated by temperature-depended photoluminescence (PL) measurements and all of the observed emission lines were well fitted by the Varshni formula.
- Published
- 2009
21. ERRATA: π0 DECAY AT CRITICAL TEMPERATURE
- Author
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Johann Rafelski and Pin-Zhen Bi
- Subjects
Physics ,Nuclear and High Energy Physics ,Condensed matter physics ,General Physics and Astronomy ,Astronomy and Astrophysics - Published
- 1992
22. The soliton solutions of the (1+1)-dimensional real ϕ4field at finite temperature
- Author
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Ru-keng Su, Pin-zhen Bi, and Guang-jiong Ni
- Subjects
Coupling ,Physics ,Field (physics) ,Condensed matter physics ,One-dimensional space ,General Physics and Astronomy ,Statistical and Nonlinear Physics ,Symmetry (physics) ,Square root ,Quantum mechanics ,Coherent states ,Soliton ,Limit (mathematics) ,Mathematical Physics - Abstract
Proposes a method based on the concepts of coherent state and the approach of the real time Green function to investigate the spontaneous breaking of symmetry in a (1+1)-dimensional phi 4 field as well as its restoration at finite temperatures. A critical temperature Tc is found at which the kink-like soliton disappears. In the weak coupling limit, the soliton mass Es mod T=Tc=(1/3 square root 3)Es mod T=0 and the critical temperature Tc=(2/3 square root 3)Es mod T=0.
- Published
- 1983
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