



02435nas a2200193   4500008004100000245011400041210006900155260001400224300001100238490000800249520181700257100002102074700002402095700001902119700002102138700001902159700002602178856003702204       2021                        eng d00aTorus Spectroscopy of the Gross-Neveu-Yukawa Quantum Field Theory: Free Dirac versus Chiral Ising Fixed Point0 aTorus Spectroscopy of the GrossNeveuYukawa Quantum Field Theory   c3/15/2021  a1251280 v1033 a<p>We establish the universal torus low-energy spectra at the free Dirac fixed point and at the strongly coupled chiral Ising fixed point and their subtle crossover behaviour in the Gross-Neuveu-Yukawa field theory with nD=4 component Dirac spinors in D=(2+1) dimensions. These fixed points and the field theories are directly relevant for the long-wavelength physics of certain interacting Dirac systems, such as repulsive spinless fermions on the honeycomb lattice or π-flux square lattice. The torus energy spectrum has been shown previously to serve as a characteristic fingerprint of relativistic fixed points and is a powerful tool to discriminate quantum critical behaviour in numerical simulations. Here, we use a combination of exact diagonalization and quantum Monte Carlo simulations of strongly interacting fermionic lattice models, to compute the critical torus energy spectrum on finite-size clusters with periodic boundaries and extrapolate them to the thermodynamic limit. Additionally, we compute the torus energy spectrum analytically using the perturbative expansion in ε=4&minus;D, which is in good agreement with the numerical results, thereby validating the presence of the chiral Ising fixed point in the lattice models at hand. We show that the strong interaction between the spinor field and the scalar order-parameter field strongly influences the critical torus energy spectrum and we observe prominent multiplicity features related to an emergent symmetry predicted from the quantum field theory. Building on these results we are able to address the subtle crossover physics of the low-energy spectrum flowing from the chiral Ising fixed point to the Dirac fixed point, and analyze earlier flawed attempts to extract Fermi velocity renormalizations from the low-energy spectrum.</p>1 aSchuler, Michael1 aHesselmann, Stephan1 aWhitsitt, Seth1 aLang, Thomas, C.1 aWessel, Stefan1 aLäuchli, Andreas, M.  uhttps://arxiv.org/abs/1907.0537302064nas a2200181   4500008004100000245007100041210006900112260001300181520150800194100001901702700001901721700001801740700001601758700002401774700002201798700002501820856003701845       2020                        eng d00aTransport and dynamics in the frustrated two-bath spin-boson model0 aTransport and dynamics in the frustrated twobath spinboson model  c7/7/20203 a<p>We study the strong coupling dynamics as well as transport properties of photons in the two-bath spin-boson model, in which a spin-1/2 particle is frustratingly coupled to two independent Ohmic bosonic baths. Using a combination of numerical and analytical methods, we show that the frustration in this model gives rise to rich physics in a very wide range of energies. This is in contrast to the one-bath spin-boson model, where the non-trivial physics occurs at an energy scale close to the renormalized spin frequency. The renormalized spin frequency in the two-bath spin-boson model is still important, featuring in different observables, including the non-equiblirum dynamics of both the spin and the baths along with the elastic transport properties of a photon. The latter however reveals a much more complex structure. The elastic scattering displays non-monotonic behavior at high frequencies, and is very different in the two channels: intra- and inter-bath scattering. The photon can also be inelastically scattered, a process in which it is split into several photons of smaller energies. We show that such inelastic processes are highly anisotropic, with the outgoing particles being preferentially emitted into only one of the baths. Moreover, the inelastic scattering rate is parameterically larger than in the one-bath case, and can even exceed the total elastic rate. Our results can be verified with state-of-the-art circuit and cavity quantum electrodynamics experiments.&nbsp;</p>1 aBelyansky, Ron1 aWhitsitt, Seth1 aLundgren, Rex1 aWang, Yidan1 aVrajitoarea, Andrei1 aHouck, Andrew, A.1 aGorshkov, Alexey, V.  uhttps://arxiv.org/abs/2007.03690