A5054492731- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Topological Materials and Phenomena
- Graphene research and applications
- Advanced Condensed Matter Physics
- Rare-earth and actinide compounds
- Superconducting Materials and Applications
- Iron-based superconductors research
- Surface and Thin Film Phenomena
- Superconductivity in MgB2 and Alloys
- Theoretical and Computational Physics
- Magnetic and transport properties of perovskites and related materials
- Quantum many-body systems
- Multiferroics and related materials
- Magnetic properties of thin films
- Quantum, superfluid, helium dynamics
- Quantum optics and atomic interactions
- Molecular Junctions and Nanostructures
- High-pressure geophysics and materials
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum Information and Cryptography
- Magneto-Optical Properties and Applications
- Inorganic Fluorides and Related Compounds
- Semiconductor Quantum Structures and Devices
- Advanced Chemical Physics Studies
National Tsing Hua University
2016-2025
Institute of Physics, Academia Sinica
2015-2024
National Center for Theoretical Sciences
2014-2023
National Center for Theoretical Sciences, Physics Division
2014-2023
Nanjing University
2001
National Chung Cheng University
1996
University of Virginia
1995
McCormick (United States)
1995
California Institute of Technology
1993
Purdue University West Lafayette
1979
Two-dimensional (2D) honeycomb lattices beyond graphene promise new physical properties such as quantum spin Hall effect. While there have been claims of growth (silicene, germanene, stanene), their existence needs further support and preparation characterization remain a difficult challenge. Our findings suggest that two distinct phases associated with the analog made germanium (Ge) instead carbon, can be grown on Ag(111) observed by scanning tunneling microscopy, low-energy electron...
A $\ensuremath{\pi}$-electron network in nanographite systems with zigzag edges exhibits strongly localized edge states, which are expected to have peculiar properties. We study effects of electron-electron interactions on ground-state properties ribbons and open-ended nanotubes by means the weak-coupling renormalization group density-matrix renormalization-group method. It is shown that ground state a spin-singlet Mott insulator finite charge spin gaps. also find states robust against...
We investigate the effects of next-nearest-neighbor ($t'$) and third-nearest-neighbor (t") hopping terms on superconductivity (SC) correlation in 2D hole-doped extended t-J model based variational Monte-Carlo (VMC), mean-field (MF) calculation, exact diagonalization (ED) method. Despite diversity methods employed, results all point to a consistent conclusion: While d-wave SC is slightly suppressed by t' t" underdoped regions, it greatly enhanced optimal overdoped regions. The T_c result upon...
Thermoelectric transport measurements of topological insulator Bi<sub>1.5</sub>Sb<sub>0.5</sub>Te<sub>1.7</sub>Se<sub>1.3</sub> nanowires reveal an enhancement the thermoelectric figure merit as compared with bulk specimen.
Measurements of spin excitations are essential for an understanding spin-mediated pairing superconductivity; and resonant inelastic X-ray scattering (RIXS) provides a considerable opportunity to probe high-energy excitations. However, whether RIXS correctly measures the collective doped superconducting cuprates remains under debate. Here we demonstrate distinct Raman- fluorescence-like Bi$_{1.5}$Pb$_{0.6}$Sr$_{1.54}$CaCu$_{2}$O$_{8+{\delta}}$ in mid-infrared energy region. Combining...
<title>Abstract</title> ARPES studies have established that the high<bold>-</bold><italic>T</italic><sub><italic>c</italic></sub> cuprates with single and double CuO<sub>2</sub> layers evolve from Mott insulator to pseudogap state a Fermi arc, on which superconducting (SC) gap opens. In four- six-layer cuprates, other hand, small hole pockets are formed in innermost planes, indicating antiferromagnetism. Here, we performed triple-layer...
Successful fabrication of α-FeTe/Bi 2 Te 3 provides a distinct platform from β-FeTe/Bi , enabling an exploration the interplay between magnetism and interface-induced superconductivity.
The reduced dynamics of a single qubit or two qubits coupled to an interacting quantum spin bath modeled by $XXZ$ chain is investigated. By using the method time-dependent density matrix renormalization group $(t\text{-DMRG})$, we go beyond uniform coupling central model and nonperturbatively evaluate induced decoherence entanglement. It shown that both entanglement strongly depend on phase underlying bath. We show in general, baths can induce for initially disentangled pair qubits....
Due to the weak spin-orbit interaction and peculiar relativistic dispersion in graphene, there are exciting proposals build spin qubits graphene nanoribbons with armchair boundaries. However, mutual interactions between electrons neglected most studies so far thus motivate us investigate role of electronic correlations nanoribbon by both analytical numerical methods. Here we show that inclusion repulsions leads drastic changes ground state turns ferromagnetic a range carrier concentrations....
Quantum phase transitions play an important role in shaping the diagram of high-temperature cuprate superconductors. These cuprates possess intertwined orders which interact strongly with superconductivity. However, evidence for quantum critical point associated charge order superconducting remains elusive. Here, we reveal short-range and spectral signature fluctuations La2−xSrxCuO4 (LSCO) near optimal doping using high-resolution resonant inelastic x-ray scattering. On performing...
A graphene nanoribbon with armchair edges is known to have no edge state. However, if the in quantum spin Hall state, then there must be helical states. By folding a ribbon into ring and threading it by magnetic flux, we study persistent charge currents tight-binding limit. It found that, for broad ribbon, current approaches finite value independent of radius ring. For narrow inter-edge coupling between states could open Dirac gap reduce overall currents. Furthermore, enhancing Rashba...
The recently synthesized silicene as well theoretically discussed germanene are examples of buckled honeycomb structures. structures allow one to manipulate asymmetry between two underlying sublattices Here by taking a prototype lattices, we explore magnetism induced breaking sublattice symmetry through saturating chemical bonds on one-side the lattice. It is shown that when fractions saturated, narrow bands always exist at half filling. Furthermore, generally support flat band...
We develop a large-N method for the problem of homogeneous turbulence. The spherical (N\ensuremath{\rightarrow}\ensuremath{\infty}) limit yields Kraichnan's direct interaction approximation equations. Implications real turbulence (N=1) are discussed. In particular, we argue that renormalization-group results obtained by setting expansion parameter y=4 incorrect, and Kolmogorov exponent \ensuremath{\zeta} has nontrivial dependence on N, with...
Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in ${\mathrm{TbMn}}_{2}{\mathrm{O}}_{5}$ arises from an internal field determined by ${\stackrel{\ensuremath{\rightarrow}}{S}}_{\stackrel{\ensuremath{\rightarrow}}{q}}\ifmmode\times\else\texttimes\fi{}{\stackrel{\ensuremath{\rightarrow}}{S}}_{\ensuremath{-}\stackrel{\ensuremath{\rightarrow}}{q}}$ with...
Based on resonant soft x-ray magnetic scattering, we report that ${\mathrm{LiCu}}_{2}{\mathrm{O}}_{2}$ exhibits a large interchain coupling which suppresses quantum fluctuations along spin chains, and quasi-2D short-range order prevails at temperatures above the transition. These observations unravel fact ground state of possesses long-range 2D-like incommensurate rather than being gapped liquid as expected from nature spin-$\frac{1}{2}$ chains. In addition, $c$ axis is found to be essential...
We generalize the dynamical large-$N$ multichannel Schwinger-boson approach to study quantum phase transition of a two-dimensional Kondo-Heisenberg model, relevant for heavy electron systems, close an antiferromagnetic Kondo destruction critical point. By breaking up singlet into charge fermion (holon) and bosonic spinon, we identify characterize from antiferromagnetically ordered state Kondo-dominated paramagnetic state, attribute jump in holon shift breakdown. calculate transport...
X-ray circular dichroism, arising from the contrast in absorption between opposite photon helicities, serves as a spectroscopic tool to measure magnetization of ferromagnetic materials and identify handedness chiral crystals. Antiferromagnets with crystallographic chirality typically lack magnetic dichroism because time-reversal symmetry, yet exhibit weak natural dichroism. Here, observation giant Ni L
In this study, a series of Bi1.5Sb0.5Te1.7Se1.3 (BSTS) flakes 80-nm to 140-μm in thickness was fabricated investigate their metallic surface states. We report the observation surface-dominated transport these topological insulator BSTS nanoflakes. The achievement can be attributed high mobility (∼3000 cm2/V s) and low bulk (12 s). Up 90% total conductance, channel estimated based on dependence electrical conductance result Shubnikov-de Hass oscillations 200-nm BSTS. nature nontrivial Dirac...
The total spectral weight $S$ of the emergent low-energy quasiparticles in high-temperature superconductors (HTSCs) is explored by x-ray absorption spectroscopy. In order to examine applicability Hubbard model, regimes that cover from zero doping overdoping are investigated. contrast results mean-field theory, we found deviates linear dependence on level $p$. slope versus $p$ changes continuously throughout whole range with no sign saturation up $p=0.23$. Therefore, picture Zhang-Rice...
We examine possible low-temperature phases of a repulsively Rydberg-dressed Fermi gas in three-dimensional free space. It is shown that the collective density excitations develop roton minimum, which softened at wave vector smaller than when particle above critical value. The mean field calculation shows that, unlike insulating states often observed conventional condensed matters, self-assembled metallic state emerges low temperatures. In particular, supports surface and body-centered-cubic...
The spectra observed in angle-resolved photoemission spectroscopy measurements are examined together with the resonance peak neutron scattering, based on slave-boson approach to $t\ensuremath{-}{t}^{\ensuremath{'}}\ensuremath{-}J$ model. We show that peak/dip/hump features arise from scattering of electrons by collective spin excitations which, at same time, give rise mode. doping dependences and dispersions positions shown be consistent experiments. recently...