ItemLandau Levels, Bardeen Polynomials, and Fermi Arcs in Weyl Semimetals: Lattice-Based Approach to the Chiral Anomaly(American Physical Society) Behrends, J.; Roy, S.; Kolodrubetz, Michael H.; Bardarson, J. H.; Grushin, A. G.; 0000-0001-5628-3300 (Kolodrubetz, M); Kolodrubetz, Michael H.Condensed matter systems realizing Weyl fermions exhibit striking phenomenology derived from their topologically protected surface states as well as chiral anomalies induced by electromagnetic fields. More recently, inhomogeneous strain or magnetization were predicted to result in chiral electric E₅ and magnetic B₅ fields, which modify and enrich the chiral anomaly with additional terms. In this Rapid Communication, we develop a lattice-based approach to describe the chiral anomaly, which involves Landau and pseudo-Landau levels and treats all anomalous terms on equal footing, while naturally incorporating Fermi arcs. We exemplify its potential by physically interpreting the largely overlooked role of Fermi arcs in the covariant (Fermi level) contribution to the anomaly and revisiting the factor of 1/3 difference between the covariant and consistent (complete band) contributions to the E₅·B₅ term in the anomaly. Our framework provides a versatile tool for the analysis of anomalies in realistic lattice models as well as a source of simple physical intuition for understanding strained and magnetized inhomogeneous Weyl semimetals. ©2019 American Physical Society. ItemFloquet Quantum Criticality(National Academy of Sciences) Berdanier, W.; Kolodrubetz, Michael; Parameswaran, S. A.; Vasseur, R.; 0000-0001-5628-3300 (Kolodrubetz, M); Kolodrubetz, MichaelWe study transitions between distinct phases of one-dimensional periodically driven (Floquet) systems. We argue that these are generically controlled by infinite-randomness fixed points of a strong-disorder renormalization group procedure. Working in the fermionic representation of the prototypical Floquet Ising chain, we leverage infinite randomness physics to provide a simple description of Floquet (multi)criticality in terms of a distinct type of domain wall associated with time translational symmetry-breaking and the formation of “Floquet time crystals.” We validate our analysis via numerical simulations of free-fermion models sufficient to capture the critical physics. ItemTopological Floquet-Thouless Energy Pump(Amer Physical Soc) Kolodrubetz, Michael H.; Nathan, Frederik; Gazit, Snir; Morimoto, Takahiro; Moore, Joel E.; 0000-0001-5628-3300 (Kolodrubetz, MH); Kolodrubetz, Michael H.We explore adiabatic pumping in the presence of a periodic drive, finding a new phase in which the topologically quantized pumped quantity is energy rather than charge. The topological invariant is given by the winding number of the micromotion with respect to time within each cycle, momentum, and adiabatic tuning parameter. We show numerically that this pump is highly robust against both disorder and interactions, breaking down at large values of either in a manner identical to the Thouless charge pump. Finally, we suggest experimental protocols for measuring this phenomenon. ItemAbsence of Thermalization in Finite Isolated Interacting Floquet Systems(Amer Physical Soc, 2018-10-22) Seetharam, Karthik; Titum, Paraj; Kolodrubetz, Michael; Refael, Gil; Kolodrubetz, MichaelConventional wisdom suggests that the long-time behavior of isolated interacting periodically driven (Floquet) systems is a featureless maximal-entropy state characterized by an infinite temperature. Efforts to thwart this uninteresting fixed point include adding sufficient disorder to realize a Floquet many-body localized phase or working in a narrow region of drive frequencies to achieve glassy nonthermal behavior at long time. Here we show that in clean systems the Floquet eigenstates can exhibit nonthermal behavior due to finite system size. We consider a one-dimensional system of spinless fermions with nearest-neighbor interactions where the interaction term is driven. Interestingly, even with no static component of the interaction, the quasienergy spectrum contains gaps and a significant fraction of the Floquet eigenstates, at all quasienergies, have nonthermal average doublon densities. We show that this nonthermal behavior arises due to emergent integrability at large interaction strength and discuss how the integrability breaks down with power-law dependence on system size.