Invited Talks
Influence matrix approach to many-body dynamics and quantum impurity models
Dmitry Abanin (University of Basel)Dynamical properties of a many-body system are determined by its properties as a quantum bath: thesystems that thermalize act as an efficient bath, while integrable and many-body localized (MBL)
systems fail to do so. I will describe a new approach to quantum many-body dynamics, inspired by thenotion of the Feynman-Vernon influence functional (IF), which captures the properties of a quantum
bath. I will consider interacting spin systems, and formulate an equation satisfied by their influencefunctionals. Surprisingly, this equation can be solved exactly for a class of many-body systems –perfect dephasers – which act as Markovian baths on their subsystems. More generally, I will show
that, viewed as a fictitious wave function in the temporal domain, influence functional can be
described by tensor-network methods. The efficiency of this approach is based on the behavior of
temporal entanglement of the IF — a quantity that I will introduce — which remains low in very
different physical regimes, including fast thermalization, integrability, and many-body
localization. Switching gears, I will argue that IF approach provides an efficient method for nonequilibrium quantum impurity models, where electrons in the leads are non-interacting. I will illustrate
this by studying quenches in the Anderson impurity model. This theoretical framework further can benaturally applied in dynamical mean-field theory algorithms.

Quantum synchronization
Christoph Bruder (University of Basel)
Experimental progress in optomechanical systems, in trapped-ion setups, and in supercon- ducting
circuit-QED architectures has motivated the study of synchronization in quantum systems. In my talk I
would like to describe theoretical approaches to the synchronization problem for quantum oscillatorsand discuss some of the issues and open questions [1-4].
[1] N. Lörch, S.E. Nigg, A. Nunnenkamp, R.P. Tiwari, and C. Bruder, Phys. Rev. Lett. 118, 243602 (2017).
[2] A. Roulet and C. Bruder, Phys. Rev. Lett. 121, 053601 (2018).
[3] A. Roulet and C. Bruder, Phys. Rev. Lett. 121, 063601 (2018).
[4] M. Koppenhöfer, C. Bruder, and A. Roulet, Phys. Rev. Research 2, 023026 (2020).

Topology of gapless and gapped phases of quantum many-body systems
Akira Furusaki (RIKEN)

Topological pump of correlated systems
Yasuhiro Hatsugai (Tsukuba University)
We have recently discussed several topological pumps of correlated systems in relation to the bulkedge correspondence where symmetry protection and U(1) gauge invariance play crucial roles[1].
After explaining the development, a topological pump of the SU(Q) quantum chain will be discussed[2].
[1] Y. Kuno and Y. Hatsugai, Phys. Rev. Research 2, 042024(R)(2020), Phys. Rev. B 104, 045113, (2021), Phys.
Rev. B 104, 125146, (2021).
[2] Y. Hatsugai and Y. Kuno, arXiv:2210.xxxxx

Spin-orbital dynamics of localized electrons
Shintaro Hoshino (Saitama University)
We propose a general framework to analyze Mott insulators from first principles calculation data.
Based on the realistic multiorbital Hubbard model, the effective model for the localized electron are
derived by the second-order perturbation theory with respect to the inter-site hopping and aredescribed by SU($N$) generators. This realistic Kugel-Khomskii model is solved by means of themean-field theory, which is identical to the dynamical mean-field theory in the strong interaction limit.
We also apply the classical Monte Carlo with the SU(N) coherent state. The present scheme can beapplied to any Mott insulators with reasonable numerical cost.

Fate of Topological Edge States in Nonunitary/Nonlinear Floquet Systems
Norio Kawakami (Kyoto University)
We discuss topological transitions in nonunitary/nonlinear time evolution of Floquet systems. We firstinvestigate nonunitary Floquet topological phases driven by PT-symmetric quantum walks. We findPT-symmetry breaking for topological edge states between regions with different bulk topologicalproperties. This theoretical prediction is confirmed experimentally for single photons by temporally
alternating photon losses. We then explore a related topic, i.e. anomalous topological edge states in anonlinear Floquet system. The linear stability analysis elucidates that Floquet stationary edge states
experience a sort of transition between two regions: edge states having extremely long or short life
time. We characterize these transitions by Krein signatures, or equivalently the pseudo-Hermiticity
breaking.

Microscopic investigation of chiral crystals
Hiroaki Kusunose (Meiji University)
We discuss the order parameter of chiral crystals and possible cross-correlated responses, based on
the symmetry-adapted multipole basis.

Theory of absorption in the frustrated 2D spin system SrCu2(BO3)2
Shin Miyahara (Fukuoka University)
The frustrated 2D spin system SrCu2(BO3)2 is realization of the Shastry-Sutherland model. Spin
excitation spectra have been investigated by ESR and IR and spin gap and bound states of two triples
excitations are observed. However, the origin and mechanism of the observations are still mystery.
We consider electromagnetic couplings in SrCu2(BO3)2 and show that the spin gap excitation and thebound states of two triplets are electro-active in the dimer singlets phase in the Shastry-Sutherlandmodel.

Unified framework on conductivities as a response to the time-dependent gauge field
Masaki Oshikawa (ISSP – University of Tokyo)
Conductivity is one of the most important characteristics of materials. Recently, nonlinear
conductivities are of increasing experimental and theoretical interest, but the subject is largely open.
In this talk I discuss our recent approach to the fundamentals of the nonlinear optical conductivities. A
system under the periodic boundary condition in one direction can be regarded as a "ring". A static
magnetic flux through the ring induces the quantum mechanical Aharonov-Bohm effect. Furthermore,increasing the flux over time induces a uniform electric field in the system. The uniform electric
conductivity can be regarded as the response of the system to the increase of the magnetic flux. Thisnot only allows a unified formulation of the "frequency sum rule" (f-sum rule).

Nonunitary Superconductivity in Complex Quantum Materials
Aline Ramires (PSI)
In this talk, I present a comprehensive discussion on nonunitary superconductivity in complex
quantum materials. Starting with a brief review of the notion of nonunitary superconductivity, I
discuss its spectral signatures in simple models with only the spin as an internal degree of freedom.
In complex materials with multiple internal degrees of freedom, there are many more possibilities forthe development of nonunitary order parameters. I provide examples focusing on d-electron systems
with two orbitals, applicable to a variety of materials. We discuss the consequences for thesuperconducting spectra, highlighting that gap openings of band crossings at finite energies can be
attributed to a nonunitary order parameter if this is associated with a finite superconducting fitness
measure. I speculate that nonunitary superconductivity in complex quantum materials is in fact very
common and can be associated with multiple cases of time-reversal symmetry breaking
superconductors.

Multiscale space-time ansatz for response functions of quantum systems
Hiroshi Shinaoka (Saitama University)
Response functions of quantum systems, which are central objects in theoretical calculations, live inhigh-dimensional space-time domains. The numerical treatment of these objects suffers from thecurse of dimensionality, which hinders the application of sophisticated many-body theories tointeresting problems. We propose a multiscale space-time ansatz for response functions of quantum
systems. The ansatz consists of two ingredients. The space-time dependence is mapped to auxiliary
qubit degrees of freedom describing exponentially different length scales. We further assume theseparation of length scales, which allows significant compression of numerical data and efficientcomputation such as Fourier transform. We numerically verify the validity of the ansatz for a variety ofsystems from equilibrium to non-equilibrium ones. Furthermore, we demonstrate numerical efficiency.

Nonlinear terahertz spectroscopy of superconductors: Higgs mode and beyond
Naoto Tsujio (University of Tokyo)
Recent advances in the nonlinear terahertz spectroscopy allows one to explore coherent dynamics
and collective excitations of superconductors in the energy scale of the superconducting gap. Amongsuch excitations exists the Higgs mode, an amplitude oscillation of the order parameter, which is acondensed-matter analog of Higgs particle in high-energy physics. I will talk about recent studies on
the Higgs mode and beyond using nonlinear terahertz spectroscopy.

Triple-q partial orders of electric quadrupoles in correlated materials
Hirokazu Tsunetsugu (ISSP - University of Tokyo)
I present our theoretical work on triple-q and other orders of electric quadruples in correlatedmaterials with a fcc lattice structure. We consider situations that a local ground state is a nonKramers doublet G3 and it has two-components of quadrupole degrees of freedom, which also couple
G3 with a singlet excited state. We have built a canonical microscopic model Hamiltonian for thosesystems and determined its mean-field phase diagram in the parameter space of two coupling
constants and temperature. One of the main results is a remarkable stability of triple-q partiallyordered phases in the high temperature region. We have analyzed their stability and instabilities
towards other ordered phases based on a phenomenological Landau theory. I also comment on aninteresting change of wavefunction’s geometrical phase upon varying the strength of quadrupole
interactions.

Nonreciprocal property and resultant optical response of superconductors
Hikaru Watanabe (University of Tokyo)
In this presentation, we present a theory of the nonreciprocal optical responses of parity-breaking
superconductors. Our results of superconducting and nonreciprocal optical responses capture themechanism similar to that in the normal state and importantly identify the anomalous mechanism. The
anomalous mechanism originates from what can appear only in the superconducting state, which wecall the nonreciprocal superfluid density and conductivity derivative.

Nonthermal electronic orders
Philipp Werner (University of Fribourg)
Recent pump-probe experiments suggest that electronic orders in correlated solids can be enhanced
or induced by nonequilibrium protocols. While the mechanisms are not always understood, theoreticalstudies have revealed relevant concepts such as entropy cooling or entropy trapping. Using thenonequilibrium generalization of dynamical mean field theory, different strategies for inducing
nonthermal electronic orders have been explored and these studies provide guiding principles for
future experiments. I will give an overview of the current theoretical results, with a focus on
nonthermal superconducting and excitonic states.

Contributed Talks
Elementary derivation of the stacking rules of invertible fermionic topological phases
in one dimension
Omer Mert Aksoy (PSI)
Invertible fermionic topological (IFT) phases are gapped phases of matter with nondegenerate groundstates on any closed spatial manifold. When open boundary conditions are imposed, nontrivial IFT
phases support gapless boundary degrees of freedom. Distinct IFT phases in one-dimensional spacewith an internal symmetry group Gf have been characterized by a triplet of indices ([(n,r)],[µ]). IFT
phases of matter form an Abelian group structure under the operation of ''stacking''. In this talk, I will
first give an operational definition of the indices ([(n,r)],[µ]) from the perspective of the boundary. I willthen show an elementary derivation of the stacking rules of IFT phases with any symmetry group Gf ,i.e., I will provide an explicit formula for ([(nÙ,rÙ)],[µÙ]) that is obtained from stacking two IFT phasescharacterized by the triplets of boundary indices ([(n1,r1],[µ1]) and ([(n2,r2],[µ2]).

Magnetoelectric classification of Skyrmions
Sayantika Bhowal (ETHZ)
We develop a general theory to classify magnetic skyrmions and related spin textures in terms of theirmagnetoelectric multipoles. Since magnetic skyrmions are now established in insulating materials,
where the magnetoelectric multipoles govern the linear magnetoelectric response, our classification
provides a recipe for manipulating the magnetic properties of skyrmions using applied electric fields.
We apply our formalism to skyrmions and anti-skyrmions of different helicities, as well as to magnetic
bimerons, which are topologically, but not geometrically, equivalent to skyrmions. We show that thenon-zero components of the magnetoelectric multipole and magnetoelectric response tensors are
uniquely determined by the topology, helicity and geometry of the spin texture. Therefore, we propose
straightforward linear magnetoelectric response measurements as an alternative to Lorentz
microscopy for characterizing insulating skyrmionic textures.

Thermal Ising Transition in the Spin-1/2 J1−J2 Heisenberg Model
Olivier Gauthé (EPFL)

The spin-1/2 Heisenberg model on the square lattice with nearest-neighbor coupling J1 and nextnearest coupling J2 (J1-J2 model) is a paradigmatic model of frustrated magnetism. Thirty years ago,
Chandra, Coleman and Larkin predicted the occurrence of a finite temperature phase transition in thismodel, however direct numerical evidence for the spin-1/2 case has been impossible to obtain so far.
Using finite-temperature tensor network algorithms, we provide the first unambiguous and direct
evidence of an Ising transition in the collinear phase of this model. We obtained consistent data thatexhibit a spontaneous breaking of the C4v symmetry, a very narrow specific heat peak and a diverging
correlation length all together.

Electronic transport in graphene with out-of-plane disorder
Yifei Guan (EPFL)
Real-world samples of graphene often exhibit various types of out-of-plane disorder--ripples, wrinkles
and folds--introduced at the stage of growth and transfer processes. These complex out-of-plane
defects resulting from the interplay between self-adhesion of graphene and its bending rigidity
inevitably lead to the scattering of charge carriers thus affecting the electronic transport properties ofgraphene. We address the ballistic charge-carrier transmission across the models of out-of-plane
defects using tight-binding and density functional calculations while fully taking into account lattice
relaxation effects. The observed transmission oscillations in commensurate graphene wrinkles are
attributed to the interference between intra- and interlayer transport channels, while theincommensurate wrinkles show vanishing backscattering and retain the transport properties of flatgraphene. The suppression of backscattering reveals the crucial role of lattice commensuration on theelectronic transmission. Our results provide guidelines to controlling the transport properties ofgraphene in presence of this ubiquitous type of disorder.

Possible restoration of particle-hole symmetry in the 5/2 Quantized Hall State at small
magnetic field
Loic Herviou (EPFL)
Motivated by the experimental observation of a quantized 5/2 thermal conductance at filling n=5/2, aresult incompatible with both the Pfaffian and the Antipfaffian states, we have pushed the expansionof the effective Hamiltonian of the 5/2 quantized Hall state to third-order in the Landau level mixing
k=Ec / hwc , where Ec is the Coulomb energy and wc the cyclotron frequency. Exact diagonalizationsof this effective Hamiltonian show that the difference in overlap with the Pfaffian and the AntiPfaffian
induced at second-order is reduced by third-order corrections and disappears around k=0.5,
suggesting that these states are much closer in energy at smaller magnetic field than previously
anticipated. Furthermore, we show that in this range of k the finite-size spectrum is typical of aquantum phase transition, with a strong reduction of the energy gap and with level crossings between
excited states. These results point to the possibility of a quantum phase transition at smaller magnetic
field into a phase with an emergent particle-hole symmetry that would explain the measured 5/2
thermal conductance of the 5/2 quantized Hall state.

Magnetoelectric Cavity Magnonics in Skyrmion Crystals
Tomoki Hirosawa (Aoyama Gakuin University)
Recently, a strong coupling between magnons and microwave photons in a cavity has attracted muchattention. While previous works have focused on the magnetic coupling between magnons andphotons via the Zeeman effect, multiferroic materials host electromagnons that can be excited byoscillating electric fields. Here, we present a theory of magnetoelectric magnon-photon coupling incavities hosting noncentrosymmetric magnets. Analogously to nonreciprocal phenomena in multiferroics, the magnetoelectric coupling is time-reversal and inversion asymmetric. This asymmetry
establishes a means for exceptional tunability of magnon-photon coupling, which can be switched on
and off by reversing the magnetization direction.
Taking the multiferroic skyrmion-host Cu2OSeO3 as an example, we reveal the electrical activity ofskyrmion eigenmodes and propose it for magnon-photon splitting of ``magnetically dark'' elliptic
modes. Furthermore, we predict a cavity-induced magnon-magnon coupling between magnetoelectrically active skyrmion excitations. We discuss applications in quantum information processing by
proposing protocols for all-electrical magnon-mediated photon quantum gates, and a photonmediated SPLIT operation of magnons. Our study shows magnetoelectric cavity magnonics as anovel platform for realizing quantum-hybrid system.

Sine-square deformed mean-field theory
Masataka Kawano (TU Munich)
We propose an efficient and unbiased protocol for evaluating quantum states with any large-scale
emergent structures. There is a growing demand to understand such phases including magnetic
skyrmions, twisted bilayer graphene, and high-Tc cuprates with doping. However, all known methods
require a prior knowledge of their structure or period, and the results often depend on numericalconditions, making it difficult to understand the nature of these phases. Our protocol, sine-square
deformed mean-field theory, overcomes this issue. We use a sine-squared envelop function to
spatially deform a real-space Hamiltonian, rendering the quantum state insensitive to the mismatch of
the order and lattice, and the result for the thermodynamic limit is already obtained for a relatively
small size. We show how our proposed method works by applying it to hole-doped and spin-orbit
coupled strongly correlated electron systems.

Kagome chiral spin liquid in transition metal dichalcogenide moiré bilayers
Johannes Motruk (University of Geneva)
Bilayers of transition metal dichalcogenides (TMDs) have recently emerged as promising platforms tostudy strongly correlated electrons in two dimensions. In particular, the low-energy physics of thesesystems can be described by extended Hubbard models on the triangular lattice. At certain fillings andparameter regimes, generalized Wigner crystals can occur in which the translational invariance of thecharge distribution is spontaneously broken. In this work, we investigate TMD heterobilayers at afilling of 3/4 holes or electrons per moiré unit cell where these are almost entirely localized on a
kagome lattice. By expanding the tight-binding model describing the system, we derive an effective
spin model on this kagome lattice that includes up to third-neighbor Heisenberg and Dzyaloshinskii–
Moriya interactions. We then employ density matrix renormalization group simulations to explore thepossibilities of realizing quantum spin liquids in this model in experimentally realistic parameter
ranges and show how WSe2/WS2 heterobilayers can be tuned to exhibit a chiral spin liquid groundstate.

Topological strongly correlated superconductor CeRh2As2
Kosuke Nogaki (Kyoto University)
The recent discovery of superconductivity in CeRh2As2 clarified an unusual H-T phase diagram with
two superconducting phases and paved a new way to realize topological superconductivity [1]. In
CeRh2As2, the inversion symmetry is locally broken at the Ce sites. Surprisingly, the phase diagram
was predicted in theoretical work about locally noncentrosymmetric superconductors [2]. The
similarity of these phase diagrams between the experiment [1] and theory [2] suggests that the local
inversion symmetry breaking plays an essential role in CeRh2As2, and the superconducting phase in
the high magnetic field region is the pair-density-wave (PDW) state. The most crucial property of thePDW state is the odd-parity superconducting state with spin-singlet pairing. The character of the PDW
state suggests a possibility of topological superconductivity as spin-triplet superconductors are.
In the first half of this talk, using the group theory, we derived the Fermi-surface formula of Z2
invariants specifying the topological crystalline superconductivity protected by the nonsymmorphic
glide symmetry [3]. Furthermore, we conducted the first-principles calculation for the electronic
structure of CeRh2As2. Combining the results, we evaluate the Z2 invariants and found the topologicalcrystalline superconductivity [4].
Despite the above success, there are some issues to be resolved. First, the microscopic mechanismof superconductivity in CeRh2As2 has not been uncovered. The experimental observations indicatethat strong correlation effects impact the electronic state of CeRh2As2. Second, although theexperimentally observed phase diagrams resemble the theoretical prediction qualitatively, the parity
transition field of the experiment is more significant than that of the weak-coupling theory by a factorof five. This discrepancy has discouraged a conclusive interpretation [1,2].
In the second half of this talk, we discuss strong correlation effects in CeRh2As2. We find XY-typemagnetic fluctuation consistent with a recent NMR study [5]. Our theoretical results also show that theparity transition field is significantly enhanced by electron correlation effects in the superconducting
phase diagram. The obtained theoretical values of the parity transition field well reproduce theexperimental value [6].
[1] S. Khim et al., Science 373, 1012 (2021).
[2] T. Yoshida, M. Sigrist, and Y. Yanase, Phys. Rev. B 86, 134514 (2012).
[3] M. Sato, Phys. Rev. B 81, 220504(R) (2010).
[4] K. Nogaki, A. Daido, J. Ishizuka, and Y. Yanase, Phys. Rev. Res. 3, L032071 (2021).
[5] S. Kitagawa et al., J. Phys. Soc. Jpn. 91, 043702 (2022).
[6] K. Nogaki and Y. Yanase, Phys. Rev. B 106, L100504 (2022).

Phonon-Mediated Spin-Triplet Superconductivity in Chiral Crystals
Rikuto Oiwa (Meiji University)
We discuss possible phonon-mediated spin-triplet pairings unique to chiral crystals, on theirmicroscopic mechanisms and pairing symmetries.

Hidden projector embedding in the Affleck-Kennedy-Lieb-Tasaki model and the PXP
model
Keita Omiya (PSI – EPFL)
Quantum many-body scar (QMBS) is a new class of weak ergodicity-breaking. Some non-integrable
models host non-thermal eigenstates called scar states which violate eigenstate thermalization
hypothesis (ETH). Since the quench experiment using Rydberg atoms showed their existence, manymodels having scar states and several recipes to construct such models have been identified.
However, the Affleck-Kennedy-Lieb-Tasaki (AKLT) model and the PXP model, an effective model ofthe experiment, have eluded thorough understanding. In this talk, I show that both the AKLT modeland the PXP model can be expressed as a generalized Shiraishi-Mori form, which is a very common
construction of Hamiltonian hosting scar states once Hilbert space is suitably enlarged. I further showa wide class of constrained models could possess this structure.

Dissipation-engineered family of nearly dark states in many-body cavity-atomsystems
Lin Rui (ETHZ)

Three-level atomic systems coupled to light have the capacity to host dark states. We study a systemof V-shaped three-level atoms coherently coupled to the two quadratures of a dissipative cavity. Theinterplay between the atomic level structure and dissipation makes the phase diagram of the open
system drastically different from the closed one. In particular, it leads to the stabilization of acontinuous family of dark and nearly dark excited many-body states with inverted atomic populations
as the steady states. The multi-stability of these states can be probed via their distinct fluctuations
and excitation spectra, as well as the system's Liouvillian dynamics which are highly sensitive to ramp
protocols. Our model can be implemented experimentally by encoding the two higher-energy modes
in orthogonal density-modulated states in a bosonic quantum gas.

Building crystalline topological superconductors from Shiba lattices
Martina Ondina Soldini (University of Zurich)
Localized or propagating Majorana boundary modes are the key feature of topological superconductors. While being a rarity in natural compounds, the tailored manipulation of quantum matter offers
novel opportunities for their realization. Specifically, lattices of Shiba bound states that arise whenmagnetic adatoms are placed on the surface of a conventional superconductor can be used to create
topological bands within the superconducting gap of the substrate. Scanning tunneling microscopy
allows to experimentally create and probe adatom lattices with single atom precision to create
topological crystalline superconductors. Their topological character and boundary modes areprotected by the spatial symmetries of the adatom lattice. We developed a theoretical model for theexperimentally realized lattices and identified signatures in the experimental measurements
consistent with the realization of two types of mirror-symmetry protected topological superconductors:(i) with full bulk gap and topological edge as well as higher-order corner states and (ii) with symmetryprotected bulk nodal points. Our results show the immense versatility of Shiba lattices to design the
topology and sample geometry of 2D superconductors.

Theoretical study of twisted bilayer Bi2(Te,Se)3
Ikuma Tateishi (RIKEN)
Recently, moiré superlattice systems, such as twisted bilayer graphene, have been very actively studied.
In this presentation, we propose twisted bilayer Bi2(Te,Se)3 as a new moiré superlattice system and show a resultof our theoretical study on its novel topological properties. Untwisted Bi2(Te,Se)3 is one of the well-known
topological insulators, and it is reported that the topological invariant of a thin film Bi2(Te,Se)3 strongly depends
on the number of stacked layers. By driving the stacking-dependent phase transition with moiré superlattice
structure, we show a twisted bilayer Bi2(Te,Se)3 has topological insulator domains and normal insulator domains
in the moiré unit cell. We also show there are corresponding edge states at the domain boundaries, and they arequantized by a finite size effect of the boundaries and result in moiré flat bands. Moreover, in the moiré band
structure, we have obtained topological insulator phases with moiré scale edge states that emerge from thedomain-boundary edge states.

Skyrmions in twisted bilayer graphene
Glenn Wagner (University of Zurich)
Twisted bilayer graphene has attracted much attention due to the correlated insulators and thesuperconductivity observed in experiments. A recent proposal by Khalaf et al. links the two: The
lowest-energy excitations of the insulating ground state are skyrmion excitations which carry one unitof charge, the excitations attract one another to form bound charge-2e objects which can thencondense to form a superconductor. I will present results from a microscopic Hartree-Fock calculationthat show that such a mechanism is a viable candidate for the superconductivity observed inexperiments.

Universal properties of dissipative Tomonaga-Luttinger liquids with and without
internal symmetry
Kazuki Yamamoto (Kyoto University)
In recent years, open quantum systems have been actively studied both experimentally andtheoretically, as exemplified by driven-dissipative many-body systems and non-Hermitian (NH)quantum systems. In particular, high controllability of ultracold atoms has enabled observations ofnovel quantum phases unique to open quantum systems. Such experimental progress has facilitatedinvestigations of NH quantum systems.
In this presentation, we demonstrate universal properties of dissipative Tomonaga-Luttinger (TL)
liquids with and without internal symmetry by deriving correlation functions and performing finite-size
scaling analysis. We first analyze a non-Hermitian XXZ spin chain as a prototypical correlated modelin one-dimensional open quantum systems [1]. Our calculation is based analytically on the field
theory with bosonization, the finite-size scaling approach in conformal field theory (CFT), and theBethe-ansatz solution, and numerically on the density-matrix renormalization group analysis
generalized to non-Hermitian systems (NH-DMRG). Importantly, we uncover that the model belongs
to the universality class characterized by the complex-valued TL parameter in the massless regime
with weak dissipation.
Then, we study universal scaling relations for dissipative TL liquids with SU(N) spin symmetry byusing asymptotic Bethe-ansatz solutions and conformal CFT in one-dimensional non-Hermitian
quantum many-body systems with SU(N) symmetry [2]. We uncover that the spectrum of dissipative
TL liquids with SU(N) spin symmetry is described by the sum of one charge mode characterized by acomplex generalization of c = 1 U(1) Gaussian CFT, and N −1 spin modes characterized by level-1
SU(N) Kac-Moody algebra with the conformal anomaly c = N −1, and thereby dissipation only affects
the charge mode as a result of spin-charge separation in one-dimensional non-Hermitian quantum
systems. The derivation is based on a complex generalization of Haldane’s ideal-gas description,
which is implemented by the SU(N) Calogero-Sutherland model with inverse-square long-range
interactions.
[1] K. Yamamoto, M. Nakagawa, M. Tezuka, M. Ueda, and N. Kawakami, Phys. Rev. B 105, 205125(2022)[2] K. Yamamoto and N. Kawakami, arXiv:2207.04395

Doping asymmetry and layer-selective metal-insulator transition in trilayer K3+xC60
Changming Yue (University of Fribourg)
Thin films provide a versatile platform to tune electron correlations and explore new physics instrongly correlated materials. Epitaxially grown thin films of the alkali-doped fulleride K3+xC60, forexample, exhibit intriguing phenomena, including Mott transitions and superconductivity, de- pending
on dimensionality and doping. Surprisingly, in the trilayer case, a strong electron-hole doping
asymmetry has been observed in the superconducting phase, which is absent in the threedimensional bulk limit. Using density-functional theory plus dynamical mean-field theory, we show that
this doping asymmetry results from a substantial charge reshuffling from the top layer to the middle

layer. While the nominal filling per fullerene is close to n = 3, the top layer rapidly switches to an n = 2
insulating state upon hole doping, which implies a doping asymmetry of the super- conducting gap.
The interlayer charge transfer and layer-selective metal-insulator transition result from the interplay
between crystal field splittings, strong Coulomb interactions, and an effectively negative Hundcoupling. This peculiar charge reshuffling is absent in the monolayer system, which is an n = 3 Mott
insulator, as expected from the nominal filling.
Ref: Changming Yue, Yusuke Nomura, Philipp Werner, Phys. Rev. Lett. 129, 066403 (2022)