A5103024871- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Semiconductor Quantum Structures and Devices
- Quantum, superfluid, helium dynamics
- Semiconductor materials and devices
- Ferroelectric and Negative Capacitance Devices
- Advancements in Semiconductor Devices and Circuit Design
- Graphene research and applications
- China's Socioeconomic Reforms and Governance
- Magnetic properties of thin films
- Social Capital and Networks
- Cold Atom Physics and Bose-Einstein Condensates
- Topological Materials and Phenomena
- Theoretical and Computational Physics
- Advanced Memory and Neural Computing
- Atomic and Subatomic Physics Research
- Surface and Thin Film Phenomena
- Interconnection Networks and Systems
- Embedded Systems Design Techniques
- Semiconductor materials and interfaces
- Magnetic Field Sensors Techniques
- Neuroscience and Neural Engineering
- VLSI and Analog Circuit Testing
- MXene and MAX Phase Materials
- Geophysics and Gravity Measurements
Fudan University
2019-2025
Shanghai Innovative Research Center of Traditional Chinese Medicine
2023
ShangHai JiAi Genetics & IVF Institute
2023
State Key Laboratory of ASIC and System
2022
University of California, Los Angeles
1997-2019
Princeton University
1989-1992
Massachusetts Institute of Technology
1989-1992
MIT Lincoln Laboratory
1992
Case Western Reserve University
1987-1991
AT&T (United States)
1990
In the high-magnetic-field low-disorder limit ground state at \ensuremath{\nu}=1/5 Landau-level filling is an incompressible quantum liquid. This determined by observing vanishing resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{x}\mathit{x}}$ as temperature T\ensuremath{\rightarrow}0. At factors below well in a narrow region above \ensuremath{\nu}=1/5, diverges exponentially contrasts T dependence any higher \ensuremath{\nu}. We conclude that liquid surrounded different phase. much...
The magnetotransport of double-quantum-well structures reveals a high-magnetic-field regime in which quantum Hall states at odd-integer \ensuremath{\nu} are missing, where is the number filled energy levels. In these double wells, \ensuremath{\nu}=odd originate from symmetric-antisymmetric gap. With increasing barrier thickness between two initially magnetic field destroys only \ensuremath{\nu}=1 state, then both and \ensuremath{\nu}=3 disappear. We attribute their destruction to onset...
We report the first experimental observation of a magnetic-field-induced transition from an Anderson insulator to quantum Hall conductor in two-dimensional electron gas (2DEG) system. With sufficiently strong disorder, 2DEG is with divergent resistance at B=0. The transformed into vanishing as T\ensuremath{\rightarrow}0 and quantized when lowest Landau level filled. observations demonstrate delocalization are consistent recently proposed global phase diagram.
This paper presents a sequence of studies on electronic transport in high-mobility, two-dimensional electron systems GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As heterostructures high magnetic fields at low Landau-level filling factors where the formation an solid has been postulated. It is extension our earlier work, summarizes findings, and compares these findings with results other investigations. We observe thermally activated insulating phase...
We show that adding a perpendicular polarizer to conventional spin torque memory element with an in-plane free layer and can significantly increase the write speed decrease energy of element. demonstrate operation such elements energies 0.4 pJ times 0.12 ns.
We have deterministically created a stable topological spin texture in magnetic tunnel junctions (MTJ) by using pulsed or microwave currents. The is characterized field-dependent intermediate resistance state and new resonance. Micromagnetic simulations show that the observations are consistent with nucleation of single skyrmion, facilitated spatially nonuniform stray field. unique resonance spectrum identified as skyrmion breathing mode diameter 75 nm estimated. This work shows possibility...
We present a study of the compressibility kappa two-dimensional hole system which exhibits metal-insulator phase transition at zero magnetic field. It has been observed that dkappa/dp changes sign critical density for transition. Measurements also indicate insulating is incompressible all values B. Finally, we show how evolves as field varied and construct diagram in density-magnetic plane this system.
We observe deep minima in the diagonal resistivity ${\ensuremath{\rho}}_{\mathrm{xx}}$ of a two-dimensional electron system GaAs at Landau-level filling factor \ensuremath{\nu}=(1/2 and (3/2. The anomalies saturate nonzero values as T\ensuremath{\rightarrow}0 persist up to temperatures \ensuremath{\sim}10 K. In spite strength features, no indication plateau development is visible Hall resistance ${\ensuremath{\rho}}_{\mathrm{xy}}$. These structures half-filling appear have their origin novel...
We present an experimental study of magnetoresistance a degenerate, two-dimensional electron gas with broad range localization length in the variable-range-hopping regime. At low magnetic fields, giant negative R(0)/R(H)\ensuremath{\sim}7 is observed and confirmed to be orbital mechanism origin. high shows contrasting transport behavior positive magnetoresistance. found transition from temperature independent occurs at field corresponding lowest Landau-level filling factor...
The conduction properties of a two-dimensional array electrons on helium film supported by dielectric substrate are reported. system undergoes metal-insulator transition at the melting point as imperfections pin lattice phase. frequency and field dependence finite-frequency conductivity noise characteristics analogous to those sliding charge-density waves.
In a two-dimensional electron system with two occupied subbands, the experimentally determined phase diagram in density-magnetic field plane exhibits rich topological features. Ringlike structures are observed at even integer filling factors diagram. Even identical quantized Hall resistance values as those given by ordinary quantum effect due to Landau level quantization, activation energies of these states within rings much smaller. These ring cannot be accounted for simple single particle...
The temperature dependences of the upper critical field ${\mathit{H}}_{\mathit{c}2}$(T) were measured over a broad range for both ${\mathrm{K}}_{3}$${\mathrm{C}}_{60}$ and ${\mathrm{Rb}}_{3}$${\mathrm{C}}_{60}$ superconductors. We found ${\mathit{H}}_{\mathit{c}2}$(0) to be 28 T 38 corresponding Ginzburg-Landau coherence length 34 30 \AA{}. H-T phase diagrams do not show qualitative difference from behavior conventional type-II superconductor.
In a two-subband $\mathrm{Ga}\mathrm{As}∕\mathrm{Al}\mathrm{Ga}\mathrm{As}$ two-dimensional electron system, the phase diagram of longitudinal resistivity ${\ensuremath{\rho}}_{xx}$ in density and magnetic field plane exhibits an intriguing structure centered at filling factor $\ensuremath{\nu}=4$ which is strikingly different from ringlike structures lower fields. Thermal activation measurements reveal anticrossing gap on each boundary where intersubband Landau levels with parallel or...
Transport measurements on gated GaAs/Al${}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterostructures over a wide range of electron densities are reported. Experimental observations the crossover from weak to strong localization compared with theoretical predictions. Agreement is found between lengths obtained hopping transport at low density and scaling theory estimate classical Drude conductivity high density.
We report measurements of the disorder-driven phase transition from a quantum Hall liquid to insulator at \ensuremath{\nu}=1/3 and \ensuremath{\nu}=2 observed in two-dimensional electron gas. The data show good scaling behavior over wide range densities temperatures with an exponent 1/zx\ensuremath{\sim}0.43 for both 2, where z is dynamical x correlation length exponent. critical conductance found be...
Resistively detected nuclear magnetic resonance (NMR) is observed inside the ringlike structure, with a quantized Hall conductance of 6e(2)/h, in phase diagram two-subband electron system. The NMR signal persists up to 470 mK and absent other states same conductance. spin-lattice relaxation time T1, found decrease rapidly towards ring center. A strong dynamic polarization by biasing current has also been only ring. These observations are consistent assertion region being ferromagnetic state...
NbOx-based devices exhibit intriguing promise for beyond-CMOS applications due to their dynamic threshold switching (TS) and negative differential resistance (NDR) behaviors. However, an in-depth study on the degradation scheme of such a device is absent. In this work, we investigate behavior, i.e., shift voltages ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {th}}$...
By tracking the delocalized states of two-dimensional hole gas in a $p$-type ${\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{A}\mathrm{l}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$ heterostructure as function magnetic field, we mapped out phase diagram density--magnetic-field plane. We found that energy state from lowest Landau level flattens field tends toward zero. This finding is different for electron system an $n$-type where diverge $B$ goes to zero indicating presence only...
Temperature dependence of the longitudinal and Hall resistances is studied in regime localization-delocalization transition. We carry out measurements scaling exponent $\ensuremath{\kappa}$ Landau level mixing region at several filling factors. The localization $\ensuremath{\gamma}$ extracted using an approach based on variable-range hopping theory. values are found to be universal independent factor our sample. can conclude that although change degeneracy a quantum state, value remains same...
Resistively detected nuclear magnetic resonance (RD-NMR) has been used to investigate a two-subband electron system in regime where quantum Hall pseudospin ferromagnet (QHPF) states are prominently developed. It reveals that the easy-axis QHPF state around total filling factor $\ensuremath{\nu}=4$ can be by RD-NMR measurement. Approaching one of Landau-level (LL) crossing points, signal strength and nuclear-spin-relaxation rate $1/{T}_{1}$ enhance significantly, signature low-energy spin...
We focus on the magnetotransport study of a two-subband GaAs/AlGaAs two-dimensional electron system in regime where there are four closely spaced energy levels, with filling factor around $\ensuremath{\nu}=4$. As we increase in-plane magnetic field, found that conventional pseudospin quantum Hall ferromagnetic states SU(2) symmetry collapsed rapidly into an unexpected state SU(4) symmetry. Within narrow tilting range angle $0.5\ifmmode^\circ\else\textdegree\fi{}$, activation increases as...