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SUMMARY:Quantum Phases and Phase Transitions in Designer Spin Models
DTSTART;VALUE=DATE-TIME:20201126T060000Z
DTEND;VALUE=DATE-TIME:20201126T070000Z
DTSTAMP;VALUE=DATE-TIME:20210115T215103Z
UID:indico-event-7867@cern.ch
DESCRIPTION:We introduce a procedure to write down lattice models with spi
n-rotation invariant Hamiltonians for arbitrary spin-S\, which can be simu
lated efficiently without a sign problem in Quantum Monte Carlo studies. A
s the first application of our approach\, we design a square lattice S = 1
model that realizes a novel “Haldane nematic” phase. This phase break
s lattice rotational symmetry by the spontaneous formation of Haldane chai
ns\, while preserving spin rotations\, time reversal and lattice translati
ons. By supplementing our model with a two-spin Heisenberg interaction\, w
e present a study of the transition between N\\'eel and Haldane nematic ph
ases\, which we find to be of first order. As another application of our p
rocedure\, we study the N\\'eel to four-fold columnar valence bond solid (
cVBS) quantum phase transition in a sign free S=1 square lattice model. Ex
tensive numerical simulations of the square lattice S=1/2 N\\'eel-VBS tran
sition have found consistency with the DCP scenario with no direct evidenc
e for first order behavior. In contrast to the S=1/2 case\, in our quantum
Monte Carlo simulations for the S=1 model\, we present unambiguous eviden
ce for a direct conventional first-order quantum phase transition.\n\nhttp
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URL:https://indico.tifr.res.in/indico/conferenceDisplay.py?confId=7867
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