Pinaki Sengupta

Bond-order-wave phase and quantum phase transitions in the one-dimensional extended Hubbard model

We use a stochastic series-expansion quantum Monte Carlo method to study the phase diagram of the one-dimensional extended Hubbard model at half-filling for small to intermediate values of the on-site U and nearest-neighbor V repulsions. We confirm the existence of a novel, long-range-ordered bond-order-wave (BOW) phase recently predicted by Nakamura [J. Phys. Soc. Jpn. 68, 3123 (1999)] in a small region of the parameter space between the familiar charge-density-wave (CDW) state for

Supersolids versus Phase Separation in Two-Dimensional Lattice Bosons

V\ensuremath{\gtrsim}U/2

Strong H...F hydrogen bonds as synthons in polymeric quantum magnets: structural, magnetic, and theoretical characterization of [Cu(HF2)(pyrazine)2]SbF6, [Cu2F(HF)(HF2)(pyrazine)4](SbF6)2, and [CuAg(H3F4)(pyrazine)5](SbF6)2.

and the state with dominant spin-density-wave (SDW) fluctuations for

Experimentally determining the exchange parameters of quasi-two-dimensional Heisenberg magnets

V\ensuremath{\lesssim}U/2.

Specific heat of quasi-two-dimensional antiferromagnetic Heisenberg models with varying interplanar couplings

We discuss the nature of the transitions among these states and evaluate some of the critical exponents. Further, we determine accurately the position of the multicritical point,

Characterization of the Antiferromagnetism in Ag(pyz)2(S2O8) (pyz = Pyrazine) with a Two-Dimensional Square Lattice of Ag2+ Ions

{(U}_{m}{,V}_{m})=(4.7\ifmmode\pm\else\textpm\fi{}0.1,2.51\ifmmode\pm\else\textpm\fi{}0.04)

Electric field modulation of the tetragonal domain orientation revealed in the magnetic ground state of quantum paraelectric EuTiO3

(in energy units where the hopping integral is normalized to unity), above which the two continuous SDW-BOW-CDW transitions are replaced by one discontinuous (first-order) direct SDW-CDW transition. We also discuss the evolution of the CDW and BOW states upon hole doping. We find that in both cases the ground state is a Luther-Emery liquid, i.e., the spin gap remains but the charge gap existing at half-filling is immediately closed upon doping. The charge and bond-order correlations decay with distance r as

Fractalization drives crystalline states in a frustrated spin system

{r}^{\ensuremath{-}{K}_{\ensuremath{\rho}}},

Interaction-Driven Metal-Insulator Transition in Strained Graphene.

where

Thermal Transport and Strong Mass Renormalization in NiCl(2)-4SC(NH(2))(2)

{K}_{\ensuremath{\rho}}