Recent content by yuanyuan5220

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    Graduate Hamiltonian with position spin coupling

    I am solving a Hamiltonian including a term \begin{equation}(x\cdot S)^2\end{equation} The Hamiltonian is like this form: \begin{equation} H=L\cdot S+(x\cdot S)^2 \end{equation} where L is angular momentum operator and S is spin operator. The eigenvalue for \begin{equation}L^2 ...
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    Graduate Low dimensional anticommutation example

    this is one example of dirac algebra, and can be generalized to clifford algebra.
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    Graduate Why isn't there a Time operator in QM?

    two papers arXiv: 0710.1128 Supplementary material to Heavy electrons and the symplectic symmetry of spin arXiv: 0810.5144 Symplectic N and time reversal in frustrated magnetism
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    Graduate Physical interpretation of unitary transformation

    the action S or hamiltonian invariant under transformations corresponds to the symmetry of the system. these transformations may be continuous( U(1), SU(2)) or discrete. while the state may not retain these symmetry--symmetry breaking.
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    Graduate LLG Equation + Spin Torque, A simple derivation

    recommend one paper on stability analysis of LLG equation with spin-polarized current prb, 76, 054414 (2007)
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    Graduate LLG Equation + Spin Torque, A simple derivation

    Hope the following link useful to you http://docs.google.com/fileview?id=0B4k0T2TYaCC2YWZiNmRlMDYtMzUwOC00YWZlLThmMzgtNzk1ZDUxYTExNzAz&hl=en Eq.(57)-Eq.(60)
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    Graduate Critical exponents for the Heisenberg AFM spin-1/2 chain

    i remember the <S_z(x)S_z(0)>=x^(1/2) For these 1d spin problems, such as xxz model and the Heisenberg model in magnetic field, the standard method is bosonization. Hope these help!
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    Graduate Ground State Energy: What Regulates & Why is it Constant?

    The ground state energy is a relative quantity. It is often defined as zero. what concerns us is the symmetry and gap.
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    Graduate Quantum field theory of condensed matter

    Recommend one book Quantum Field Theory of Many-Body Systems by Xiao-gang Wen
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    Graduate Is the Ground State Energy of the Two-Dimensional XX Model Known?

    Jordan-wigner transformation is useful for 1/2 spin system i don't remember the Hamiltonian of xx model, but for 2 d system, seems difficult to sovle it exactly. some numerical methods, like lanczos algorithm ,VMC... try some old archives in prl and prb at 1980s...
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    Graduate The Role of Phonons in High Temperature Superconductivity

    The 2-dimensional 1/2 spin Heisenberg model is the key problem in the copper oxide superconductor. For the 1-D 1/2 spin antiferromagnetic Heisenberg model, it has been exactly solved by bethe ansatz. And the low-energy excitation can be analyzed be many methods, such as Bosonizaiton, RG... In...