Qiang Han

South China University of Technology

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Andrew J. Millis

Columbia University

Z. D. Wang

University of Electronic Science and Technology of China

Liyuan Zhang

Peking University

Dan-Bo Zhang

South China Normal University

Zhidan Li

Shenzhen University

Tian‐Long Xia

Renmin University of China

X.-G. Li

Collaborative Innovation Center of Advanced Microstructures

Yao Xiao-Hu

Tao Li

Shanghai Industrial Technology Institute

Liyuan Zhang

Southern University of Science and Technology

Cooperative Institutions

Chinese Academy of Sciences

University of Hong Kong

University of Science and Technology of China

Renmin University of China

Columbia University

University of Michigan–Ann Arbor

Nanjing University

University of Chinese Academy of Sciences

Stony Brook University

Hefei National Center for Physical Sciences at Nanoscale

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Monte Carlo study of thermal fluctuations and Fermi-arc formation ind-wave superconductors

Physical Review B (2011)

Yong‐Wei Zhong Tao Li Qiang Han

From the perspective of thermal fluctuations, we investigate the pseudogap phenomena in underdoped high-temperature curpate superconductors. We present a local update Monte Carlo procedure based on the Green's function method to sample the fluctuating pairing field. The Chebyshev polynomial method is applied to calculate the single-particle spectral function directly and efficiently. The evolution of Fermi arcs as a function of temperature is studied by examining the spectral function at Fermi energy as well as the loss of spectral weight. Our results signify the importance of the vortex-like phase fluctuation on the formation of Fermi arcs.

Pseudogap

10.1103/physrevb.84.024522

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Citations (9)

Flexoelectric effect on bandgap properties of periodic bi-directional-graded curved nanoshells

European Journal of Mechanics - A/Solids (2024)

Shanhong Lin Qiang Han Chunlei Li

Nanoshell

10.1016/j.euromechsol.2024.105504

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Topological properties of Mo2C and W2C superconductors

Physical review. B./Physical review. B (2020)

Ning-Ning Zhao Peng‐Jie Guo Xiao-Qin Lu Qiang Han Kai Liu

The topological electronic properties of orthorhombic-phase Mo$_{2}$C and W$_{2}$C superconductors have been studied based on first-principles electronic structure calculations. Our studies show that both Mo$_{2}$C and W$_{2}$C are three-dimensional strong topological insulators defined on curved Fermi levels. The topological surface states on the (001) surface of Mo$_{2}$C right cross the Fermi level, while those of W$_{2}$C pass through the Fermi level with slight electron doping. These surface states hold helical spin textures and can be induced to become superconducting via a proximity effect, giving rise to an equivalent $p+ip$ type superconductivity. Our results show that Mo$_{2}$C and W$_{2}$C can provide a promising platform for exploring topological superconductivity and Majorana zero modes.

10.1103/physrevb.101.195144

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Citations (15)

On the origin of the Fermi arc phenomenon in the underdoped cuprates: signature of KT-type superconducting transition

Journal of Physics Condensed Matter (2011)

Tao Li Qiang Han

The origin of the Fermi arc phenomenon in the pseudogap phase of the underdoped cuprates is studied in the thermal phase fluctuation scenario. An XY-type lattice model with a built in d-wave structure is introduced to describe the phase fluctuation effect in the cuprates. A sharp ridge-like structure in the spectral function A(k, ω = 0) is found to emerge abruptly above the Kosterlitz-Thouless (KT) transition temperature (T(KT)) on the underlying Fermi surface. This ridge-like structure in A(k, ω = 0) bears a close resemblance to the observed Fermi arc phenomenon in its temperature dependence and shape in the momentum space. These results provide yet more strong evidence for the KT transition nature of the superconducting transition in the underdoped cuprates.

Pseudogap

10.1088/0953-8984/23/10/105603

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Citations (3)

Unconventional Fulde-Ferrel-Larkin-Ovchinnikov states in spin-orbit coupled condensates: exact results

arXiv (Cornell University) (2011)

Qiang Han Jia Liu Dan-Bo Zhang Z. D. Wang

We find that a model Hamiltonian of s-wave superconductors in the presence of spin-orbit interactions and a Zeeman field is exactly solvable. Most intriguingly, based on the exact solutions, an unconventional type of Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) ground state is rigorously revealed, in which the center-of-mass momentum of the fermion pair is proportional to the Zeeman field. We also elaborate on the drifting effect of the Zeeman field on the spin-orbit-coupled Bose-Einstein condensate.

Orbit (dynamics)

10.48550/arxiv.1104.0614

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Citations (2)

Nuclear spin relaxation rate of disorderedpx+ipy-wave superconductors

Physical Review B (2004)

Qiang Han Z. D. Wang

Based on an effective Hamiltonian with the binary alloy disorder model defined in the triangular lattice, the impurity scattering effects on the density of states and especially on the spin-lattice relaxation rate $1∕{T}_{1}$ of ${p}_{x}+i{p}_{y}$-wave superconductors are studied by solving numerically the Bogoliubov--de Gennes equations. In the clean limit, the coherence peak of $1∕{T}_{1}$ is observed as expected. More intriguingly, for strong scattering potential, the temperature dependence of $1∕{T}_{1}$ exhibits the two different power-law behaviors near ${T}_{\mathrm{c}}$ and at low temperatures, respectively, which is qualitatively consistent with the nuclear quadrupolar resonance measurement of the newly discovered superconductor ${\mathrm{Na}}_{x}\mathrm{Co}{\mathrm{O}}_{2}∙y{\mathrm{H}}_{2}\mathrm{O}$ $(x=0.35)$. We argue that the disorder effect plays an important role in the thermodynamic properties of the ${p}_{x}+i{p}_{y}$-wave pairing state as indicated in this paper, as well as other superconducting states with unconventional pairing symmetries. Therefore further experimental exploration is expected to determine the actual pairing symmetry of this material.

Hamiltonian (control theory)

10.1103/physrevb.70.184504

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Citations (3)

Pseudogap and Fermi-arc evolution in the phase-fluctuation scenario

Physical Review B (2010)

Qiang Han Tao Li Z. D. Wang

Pseudogap phenomena and the formation of Fermi arcs in underdoped cuprates are numerically studied in the presence of phase fluctuations that are simulated by an $XY$ model. Most importantly the spectral function for each Monte Carlo sample is calculated directly and efficiently by the Chebyshev polynomials without having to diagonalize the fermion Hamiltonian, which enables us to handle a system large enough to achieve sufficient momentum/energy resolution. We find that the momentum dependence of the energy gap is identical to that of a pure $d$-wave superconductor well below the Kosterlitz-Thouless (KT) transition temperature $({T}_{\text{KT}})$ while displays an upturn deviation from $\text{cos}\text{ }{k}_{x}\ensuremath{-}\text{cos}\text{ }{k}_{y}$ with increasing temperature. An abrupt onset of the Fermi arcs is observed above ${T}_{\text{KT}}$ and the arc length exhibits a similar temperature dependence to the thermally activated vortex excitations.

Pseudogap

Hamiltonian (control theory)

Momentum (technical analysis)

10.1103/physrevb.82.052503

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Citations (15)

Length Dependent Material Properties of Carbon Nanotubes

Journal of Computational and Theoretical Nanoscience (2008)

Q. Wang Qiang Han Bo Wen

Carbon fibers

10.1166/jctn.2008.2590

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Citations (1)

Influences of atom vacancies on buckling properties of armchair single-walled carbon nanotubes shown by molecular dynamics simulation

Acta Physica Sinica (2008)

Hao Xin Qiang Han Yao Xiao-Hu

Molecular dynamics simulations are employed to simulate the axial compression of both perfect and defective armchair single-walled carbon nanotubes (SWCNTs). Three temperature conditions are considered. It is revealed that the vacancy defects in SWCNTs have remarkable influences on their buckling properties, especially at low temperature. It is noticed that the single vacancy defect leads to excessive stress concentration, as a result of which the local buckling occurs easily at the defective position. Thus, the (7, 7) tube with single vacancies seems inferior to that with double vacancies.

10.7498/aps.57.4391

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Citations (4)

EFFECT OF OXYGEN DOPING AND HIGH PRESSURE ON THE ELECTRONIC STRUCTURE OF HgBa₂CuO_4+δ AND SUPERCONDUCTIVITY

International Journal of Modern Physics B (2001)

Shuang Zhang Qiang Han Liyuan Zhang

The effects of oxygen doping (δ=0~0.19) and high pressure (P=0~5.07 GPa) on the electronic structure of HgBa 2 CuO 4+δ have been studied by the recursion method. The hole concentration of the CuO 2 layer increases monotonically as δ increases from 0 to 0.19. Each excess oxygen atom contributes about 1.9 holes to the CuO 2 layer. The pressure-induced charge transfer, dn/dP, decreases for increasing δ, vanishing at over-doping level, which is consistent with the δ-dependence of dT c /dP observed in experiments.

10.1142/s021797920100485x

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