v1.8.0

FiniteMPS v1.8.0

Diff since v1.7.2

• support adaptive step length for tanTRG
• support effective temperature in 1-DMRG to support annealing method
• modify implementation of noise in mul and axpby
• fix type mismatch error in spin-fermion mixed systems (e.g. Kondo lattice)

v1.7.2

FiniteMPS v1.7.2

Diff since v1.7.1

• modify noise algorithm in mul! and axpby!
• add spin bond operators in U1SU2Fermion and corresponding tests
• minor bug fix

Merged pull requests:

• add spin nematic correlator for U1Spin case S++-- (#14) (@phyjswang)

v1.7.1

FiniteMPS v1.7.1

Diff since v1.7.0

• fix bug: MethodError when adding 4-site correlations to ObservableTree.

v1.7.0

FiniteMPS v1.7.0

Diff since v1.6.1

A stable version after merging a sequence of commits in dev branch.

Closed issues:

• Unexpected Behavior in addIntr! When Handling Symmetric all-to-all Interactions (#11)

v1.6.1

FiniteMPS v1.6.1

Diff since v1.6.0

• fix MethodError for LocalOperator + LocalOperator
• update example

v1.6.0

FiniteMPS v1.6.0

Diff since v1.5.0

Breaking changes

• Rewrite addIntr! and addObs! and change the interface. For example, consider a hopping term, now the usage becomes

addIntr!(Root, (Fdag, F), (i, j), (true, true), strength; Z = Z)

where (true, true) means both operators are fermionic. Similarly,

addObs!(Tree, (Fdag, F), (i, j), (true, true); Z = Z)

for the calculation of single-particle correlations.

• Now a multi-site correlation with duplicated site indices can automatically reduce to a shorter term. For example, in the case of $U_1 \times SU_2$ symmetry, the pairing correlation $\langle \Delta_{12}^\dagger \Delta_{23}\rangle$ can be simply calculated via

addObs!(Tree, U1SUFermions.ΔₛdagΔₛ, (1, 2, 2, 3), (true, true, true, true); Z = U1SUFermions.Z)

• Support adding 3-site terms, e.g. chiral operator $S_i \cdot (S_j \times S_k)$ pinning field, to the Hamiltonian.

Merged pull requests:

• ensure MPS used in calObs! is canonicalized at the first site (#7) (@phyjswang)
• Add addIntr3! and U₁SU₂ operator SSS (#10) (@Asmendeus)

v1.5.0

FiniteMPS v1.5.0

Diff since v1.4.2

New Features

Support the computation of imaginary-time proxy (ITP)

ITP forms like $\langle A(\beta/2) B\rangle_\beta = Z^{-1}{\rm Tr}\{e^{-\beta H/2} A e^{-\beta H/2} B\}$, which can be directly obtained with the thermal density operator $e^{-\beta H/2}$ represented as MPO. We provide the following interfaces for users.

• A concrete type ImagTimeProxyGraph to describe the terms to be calculated.
• addITP2! and addITP4! for adding terms like $\langle A_i(\beta/2) B_j\rangle_\beta$ and $\langle A_i(\beta/2) B_j(\beta/2) C_k D_l \rangle_\beta$, respectively.
• merge! to compress the graph partially.
• calITP! for in-place calculation.

Detailed usage please see the documentation via ? in REPL.

Example

The following shows a sample code for the calculation of the single particle Green's function $\langle c_i^\dagger(\beta/2) c_j\rangle_\beta$ with $U_1\times SU_2$ symmetry.

G = ImagTimeProxyGraph(L)
for i in 1:L, j in i:L
    addITP2!(G, U1SU2Fermion.FdagF, (i, j), (:Fdag, :F); Z=U1SU2Fermion.Z)
end
merge!(G)
calITP!(G, rho)

where rho is a length-L MPO that represents $Z^{-1/2}e^{-\beta H/2}$. After this, the value of $\langle c_i^\dagger(\beta/2) c_j\rangle_\beta$ is stored at

G.Refs["FdagF"][(i, j)][]

There may exist bugs that have not yet been discovered, please check carefully with the results.

Other changes

• Update dependent packages such as TensorKit.jl and KrylovKit.jl.

Closed issues:

• ERROR: MethodError: Cannot convert an object of type ObservableTree{1} to an object of type Dict (#5)

v1.4.2

FiniteMPS v1.4.2

Diff since v1.4.1

fixed bugs

• throw an error when the step length in Krylov-based exponentiate is too large, which may lead to a dead loop in previous versions
• force to normalize the output state after DMRG sweep

new features

• add serial mode in calObs! for debugging
• add auto swap in addIntr4!, with which we can compute the 4-site correlation (i, j, k, l) with i > j or k > l now
• add U1U1tJFermion in LocalSpace, i.e. d=3 physical space in tJ model with $U_1$ (charge) $\times U_1$ (spin) symmetry

v1.4.1

FiniteMPS v1.4.1

Diff since v1.4.0

• fix ambiguous method error of convert in Julia v1.9

v1.4.0

FiniteMPS v1.4.0

Diff since v1.3.0

• fix the bug in ObservableTree which may give an incorrect sign for some 4-site fermionic correlations.
• note the type parameter of the tree nodes in ObservableTree is different from old versions.
• rewrite the implementation (method convert) for extracting the values stored in ObservableTree. The usage changes from

convert(Type, Tree::ObservableTree, name::NTuple{N, String})

to

convert(Type, Tree::ObservableTree)

where the supported Type contains Dict and NamedTuple. Passing in the name that corresponds to the correlation is no long needed.