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Parameter: issus

Definition

It is a key control flag, which is used to determine whether we should measure the charge or spin susceptibility and which one we should measure.

Type

Integer

Default value

1

Component

Only for the GARDENIA, NARCISSUS, LAVENDER, CAMELLIA, and MANJUSHAKA components.

Behavior

We just use the following algorithm to judge which susceptibility should be calculated:

  • issus parameter is converted from a decimal representation to a binary representation at first. For example, 10$_{10}$ is converted to 1010$_{2}$, 15$_{10}$ is converted to 1111$_{2}$, etc.

  • Then we examine the bits from rightmost to leftmost one by one. If it is 1, then we do the calculation specified by this bit. If it is 0, then we ignore the calculation specified by this bit. For example, we just use the second bit (from right side to left side) to represent the calculation of spin-spin correlation function. Therefore, if issus parameter is 10$_{10}$ (1010$_{2}$), we will calculate the spin-spin correlation function since the second bit is 1. Supposing issus parameter is 13$_{10}$ (1101$_{2}$), we will not calculate it as the second bit is 0.

The following are the definitions of bit representation [p is the bit order (from right to left side)]:

  • p = 1, do nothing

  • p = 2, calculate spin-spin correlation function (in time space)

  • p = 3, calculate orbital-orbital correlation function (in time space)

  • p = 4, calculate spin-spin correlation function (in frequency space)

  • p = 5, calculate orbital-orbital correlation function (in frequency space)

  • p = 6, calculate $\langle k^2 \rangle - \langle k \rangle^2$

  • p = 7, calculate fidelity susceptibility matrix

  • p = 8, reserved

  • p = 9, reserved

Now let's consider a concrete example.

Supposed that issus = 469$_{10}$, then the corresponding binary representation is 111010101$_{2}$. And then we can easily obtain that:

  • p = 9, bit = 1

  • p = 8, bit = 1

  • p = 7, bit = 1

  • p = 6, bit = 0

  • p = 5, bit = 1

  • p = 4, bit = 0

  • p = 3, bit = 1

  • p = 2, bit = 0

  • p = 1, bit = 1

According to the previous definitions about the bit representation, we can conclude that the quantum impurity solvers should calculate the orbital-orbital correlation function (in time space and frequency space) and the fidelity susceptibility simultaneously.

For the CAMELLIA, LAVENDER, and MANJUSHAKA components, the bits at p = 2, 3, 4, and 5 are not ready.

Comment

The spin-spin correlation function will be written into the solver.schi.dat and solver.sfom.dat files. The orbital-orbital correlation function will be written into the solver.ochi.dat and solver.ofom.dat files. The kinetic energy fluctuation will be written into the solver.kmat.dat file. The fidelity susceptibility will be written into the solver.lmat.dat file.

The Green's function $G(\tau)$ and $G(i\omega_n)$, hybridization function $\Delta(\tau)$ and $\Delta(i\omega_n)$, and self-energy function $\Sigma(i\omega_n)$ will be calculated and output by the quantum impurity solvers in the iQIST software package implicitly. However, the susceptibilities and high-order correlation functions won't. You have to use the issus and isvrt parameters to active the related calculations.

See isvrt for more details.