Joint ICTP/SISSA Statistical Physics Seminar, 6 May at 11:00am, by Yasir Iqbal

[CMSP Seminars Secretariat]

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Joint ICTP/SISSA Statistical Physics Seminar
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** * * Tuesday 6 May**2025, 11:00**am ***(CET)** * **
*Luigi Stasi Seminar Room **(Leonardo Building, first floor)***
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/Zoom: 
https://zoom.us/meeting/register/rwIL4MlHSpmze4NHETHAIw/<https://zoom.us/meeting/register/tJIsfuuhqjsrE9EZY2loNxNobg8Lf39NUVHJ>

Speaker:*Yasir Iqbal *(Indian Institute of Technology Madras)

Title: *Evidence for a ℤ2 Dirac spin liquid in the generalized 
Shastry-Sutherland model
*

Abstract:
We present a multimethod investigation into the nature of the recently 
reported quantum spin liquid (QSL) phase in the spin-1/2 Heisenberg 
antiferromagnet on the Shastry-Sutherland lattice. A comprehensive 
projective symmetry group classification of fermionic mean-field Ansätze 
on this lattice yields 46 U(1) and 80 ℤ2 states. Motivated by 
density-matrix renormalization group (DMRG) calculations suggesting that 
the Shastry-Sutherland model and the square-lattice J1-J2 Heisenberg 
antiferromagnet putatively share the same QSL phase, we establish a 
mapping of our Ansätze to those of the square lattice. This enables us 
to identify the equivalent of the square-lattice QSL (Z2Azz13) in the 
Shastry-Sutherland system. Employing state-of-the-art variational Monte 
Carlo calculations with Gutzwiller-projected wavefunctions improved upon 
by Lanczos steps, we demonstrate the excellent agreement of energies and 
correlators between a gapless (Dirac) ℤ2 spin liquid -- characterized by 
only few parameters -- and approaches based on neural quantum states and 
DMRG. Furthermore, the real-space spin-spin correlations are shown to 
decay with the same power law as in the J1-J2 square lattice model, 
which also hosts a ℤ2 Dirac spin liquid. Finally, we apply the recently 
developed Keldysh formulation of the pseudo-fermion functional 
renormalization group to compute the dynamical spin structure factor; 
these correlations exhibit the features expected due to Dirac cones in 
the excitation spectrum, thus providing strong independent evidence for 
a Dirac QSL ground state. Our finding of a d-wave pairing ℤ2 Dirac QSL 
is consistent with the recently observed signatures of QSL behavior in 
Pr2Ga2BeO7 and outlines predictions for future experiments.