TY  - JOUR
PB  - SciPost Foundation
DO  - 10.21468/SciPostPhys.4.6.044
TI  - Resonating valence bonds and spinon pairing in the Dicke model
PY  - 2018/06/30
UR  - https://www.scipost.org/SciPostPhys.4.6.044
JF  - SciPost Physics
JA  - SciPost Phys.
VL  - 4
IS  - 6
SP  - 044
A1  - Ganesh, R.
AU  - Theerthagiri, L.
AU  - Baskaran, Ganapathy
AB  - Resonating valence bond (RVB) states are a class of entangled quantum many body wavefunctions with great significance in condensed matter physics. We propose a scheme to synthesize a family of RVB states using a cavity QED setup with two-level atoms (with states $\vert 0 \rangle$ and $\vert 1 \rangle$) coupled to a common photon mode. In the lossy cavity limit, starting with an initial state of $M$ atoms excited and $N$ atoms in the ground state, we show that this setup can be configured as a Stern Gerlach experiment. A measurement of photon emission collapses the wavefunction of atoms onto an RVB state composed of resonating long-ranged singlets of the form $\frac{1}{\sqrt{2}}[\vert 0 1 \rangle - \vert 1 0 \rangle]$. Each emitted photon reduces the number of singlets by unity, replacing it with a pair of lone spins or `spinons'. As spinons are formed coherently in pairs, they are analogous to Cooper pairs in a superconductor. To simulate pair fluctuations, we propose a protocol in which photons are allowed to escape the cavity undetected. This leads to a mixed quantum state with a fluctuating number of spinon pairs -- an inchoate superconductor. Remarkably, in the limit of large system sizes, this protocol reveals an underlying quantum phase transition. Upon tuning the initial spin polarization ($M-N$), the emission exhibits a continuous transition from a dark state to a bright state. This is reflected in the spinon pair number distribution which can be tuned from sub-poissonian to super-poissonian regimes. This opens an exciting route to simulate RVB states and superconductivity.
ER  -

@Article{10.21468/SciPostPhys.4.6.044,
	title={{Resonating valence bonds and spinon pairing in the Dicke model}},
	author={R. Ganesh and L. Theerthagiri and G. Baskaran},
	journal={SciPost Phys.},
	volume={4},
	pages={044},
	year={2018},
	publisher={SciPost},
	doi={10.21468/SciPostPhys.4.6.044},
	url={https://scipost.org/10.21468/SciPostPhys.4.6.044},
}