Efficient density matrix renormalization group algorithm to study Y junctions with integer and half-integer spin
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2016-02-03Permanent link to this record
http://hdl.handle.net/10754/601364
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An efficient density matrix renormalization group (DMRG) algorithm is presented and applied to Y junctions, systems with three arms of n sites that meet at a central site. The accuracy is comparable to DMRG of chains. As in chains, new sites are always bonded to the most recently added sites and the superblock Hamiltonian contains only new or once renormalized operators. Junctions of up to N=3n+1≈500 sites are studied with antiferromagnetic (AF) Heisenberg exchange J between nearest-neighbor spins S or electron transfer t between nearest neighbors in half-filled Hubbard models. Exchange or electron transfer is exclusively between sites in two sublattices with NA≠NB. The ground state (GS) and spin densities ρr=⟨Szr⟩ at site r are quite different for junctions with S=1/2, 1, 3/2, and 2. The GS has finite total spin SG=2S(S) for even (odd) N and for MG=SG in the SG spin manifold, ρr>0(<0) at sites of the larger (smaller) sublattice. S=1/2 junctions have delocalized states and decreasing spin densities with increasing N. S=1 junctions have four localized Sz=1/2 states at the end of each arm and centered on the junction, consistent with localized states in S=1 chains with finite Haldane gap. The GS of S=3/2 or 2 junctions of up to 500 spins is a spin density wave with increased amplitude at the ends of arms or near the junction. Quantum fluctuations completely suppress AF order in S=1/2 or 1 junctions, as well as in half-filled Hubbard junctions, but reduce rather than suppress AF order in S=3/2 or 2 junctions.Citation
Efficient density matrix renormalization group algorithm to study Y junctions with integer and half-integer spin 2016, 93 (7) Physical Review BSponsors
M.K. thanks DST for support through Ramanujan Fellowship No. SR/S2/RJN-69/2012 and DST for funding computation facility through Grant No. SNB/MK/14-15/137. Z.G.S. thanks NSF for partial support of this work through the Princeton MRSEC (Grant No. DMR-0819860). S.R. thanks DST India for financial support.Publisher
American Physical Society (APS)Journal
Physical Review BISSN
2469-99502469-9969
Additional Links
http://link.aps.org/doi/10.1103/PhysRevB.93.075107ae974a485f413a2113503eed53cd6c53
10.1103/PhysRevB.93.075107