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Dive into the research topics where Maria Hermanns is active.

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Featured researches published by Maria Hermanns.


Physical Review B | 2016

Classification of gapless Z2 spin liquids in three-dimensional Kitaev models

Kevin O'Brien; Maria Hermanns; Simon Trebst

Frustrated quantum magnets can harbor unconventional spin liquid ground states in which the elementary magnetic moments fractionalize into new emergent degrees of freedom. While the fractionalization of quantum numbers is one of the recurring themes in modern condensed matter physics, it often remains a challenge to devise a controlled analytical framework tracking this phenomenon. A notable exception is the exactly solvable Kitaev model, in which spin degrees of freedom fractionalize into Majorana fermions and a Z2 gauge field. Here we discuss the physics of fractionalization in three-dimensional Kitaev models and demonstrate that the itinerant Majorana fermions generically form a (semi)metal which, depending on the underlying lattice structure, exhibits Majorana Fermi surfaces, nodal lines or topologically protected Weyl nodes. We show that the nature of these Majorana metals can be deduced from an elementary symmetry analysis of the projective time-reversal and inversion symmetries for a given lattice. This allows us to comprehensively classify the gapless spin liquids of Kitaev models for the most elementary tricoordinated lattices in three dimensions. We further expand this classification by addressing the effects of time-reversal symmetry breaking and additional interactions.


Physical Review B | 2011

Bulk-Edge Correspondence in the Entanglement Spectra

Anushya Chandran; Maria Hermanns; Nicolas Regnault; B. Andrei Bernevig

Li and Haldane conjectured and numerically substantiated that the entanglement spectrum of the reduced density matrix of ground-states of time-reversal breaking topological phases (fractional quantum Hall states) contains information about the counting of their edge modes when the ground-state is cut in two spatially distinct regions and one of the regions is traced out. We analytically substantiate this conjecture for a series of FQH states defined as unique zero modes of pseudopotential Hamiltonians by finding a one to one map between the thermodynamic limit counting of two different entanglement spectra: the particle entanglement spectrum, whose counting of eigenvalues for each good quantum number is identical (up to accidental degeneracies) to the counting of bulk quasiholes, and the orbital entanglement spectrum (the Li-Haldane spectrum). As the particle entanglement spectrum is related to bulk quasihole physics and the orbital entanglement spectrum is related to edge physics, our map can be thought of as a mathematically sound microscopic description of bulk-edge correspondence in entanglement spectra. By using a set of clustering operators which have their origin in conformal field theory (CFT) operator expansions, we show that the counting of the orbital entanglement spectrum eigenvalues in the thermodynamic limit must be identical to the counting of quasiholes in the bulk. The latter equals the counting of edge modes at a hard-wall boundary placed on the sample. Moreover, we show this to be true even for CFT states which are likely bulk gapless, such as the Gaffnian wavefunction.


Physical Review Letters | 2015

Weyl spin liquids.

Maria Hermanns; Kevin O'Brien; Simon Trebst

The fractionalization of quantum numbers in interacting quantum many-body systems is a central motif in condensed-matter physics with prominent examples including the fractionalization of the electron in quantum Hall liquids or the emergence of magnetic monopoles in spin-ice materials. Here, we discuss the fractionalization of magnetic moments in three-dimensional Kitaev models into Majorana fermions (and a Z_{2} gauge field) and their emergent collective behavior. We analytically demonstrate that the Majorana fermions form a Weyl superconductor for the Kitaev model on the recently synthesized hyperhoneycomb structure of β-Li_{2}IrO_{3} when applying a magnetic field. We characterize the topologically protected bulk and surface features of this state, which we dub a Weyl spin liquid, including thermodynamic and transport signatures.


Reviews of Modern Physics | 2017

Quantum Hall physics : Hierarchies and conformal field theory techniques

Thors Hans Hansson; Maria Hermanns; S. H. Simon; Susanne Viefers

The fractional quantum Hall effect, being one of the most studied phenomena in condensed matter physics during the past 30 years, has generated many ground-breaking new ideas and concepts. Very ear ...


Physical Review B | 2015

Spin-orbit physics ofj=12Mott insulators on the triangular lattice

Michael Becker; Maria Hermanns; Bela Bauer; Markus Garst; Simon Trebst

The physics of spin-orbital entanglement in effective


Physical Review B | 2014

Quantum spin liquid with a Majorana Fermi surface on the three-dimensional hyperoctagon lattice

Maria Hermanns; Simon Trebst

j=\frac{1}{2}


Physical Review B | 2011

Haldane Statistics in the Finite Size Entanglement Spectra of Laughlin States

Maria Hermanns; A. Chandran; Nicolas Regnault; B. Andrei Bernevig

Mott insulators, which have been experimentally observed for various


Physical Review B | 2008

Quantum Hall wave functions on the torus

Maria Hermanns; Juha Suorsa; Emil J. Bergholtz; Thors Hans Hansson; Anders Karlhede

5d


Physical Review Letters | 2007

Microscopic theory of the quantum Hall hierarchy.

Emil J. Bergholtz; Thors Hans Hansson; Maria Hermanns; Anders Karlhede

transition-metal oxides, has sparked an interest in Heisenberg-Kitaev (HK) models thought to capture their essential microscopic interactions. Here, we argue that the recently synthesized


Journal of Statistical Mechanics: Theory and Experiment | 2014

Entanglement spectrum and entanglement Hamiltonian of a Chern insulator with open boundaries

Maria Hermanns; Yann Salimi; Masudul Haque; Lars Fritz

{\mathrm{Ba}}_{3}{\mathrm{IrTi}}_{2}{\mathrm{O}}_{9}

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Simon Trebst

University of California

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