We report angle-resolved electron transmission measurements through freestanding graphene sheets in the energy range of 18 to 30 eV above the Fermi level. The measurements are carried out in a low-energy electron point source microscope, which allows simultaneously probing the transmission for a large angular range. The characteristics of low-energy electron transmission through graphene depend on its electronic structure above the vacuum level. The experimental technique described here allows mapping of the unoccupied band structure of freestanding two-dimensional materials as a function of the energy and probing angle, respectively, in-plane momentum. Our experimental findings are consistent with theoretical predictions of a resonance in the band structure of graphene above the vacuum level [V. U. Nazarov, E. E. Krasovskii, and V. M. Silkin, Phys. Rev. B 87, 041405 (2013)].

We report first principles investigations of the anomalous Hall effect (AHE) in Fe and Ni four-probe crossbar nanostructures where the boundary scattering is a very important mechanism for the predicted AHE resistance. The results allow us to understand nanoscopic AHE physics in terms of how quantized channels are scattered by boundaries to contribute to the AHE resistance, the spin orbit interaction (SOI) versus boundary scattering, the spin texture of the scattered channels, and the symmetry of the scattering matrices. From individual transport channels we find that electrons are pushed in the transverse direction deep inside the incoming probe by the SOI, and strongly scattered by the crossbar boundaries to negotiate corners and enter into voltage probes. The combined SOI and boundary scattering lead to opposite signs of the AHE resistance for Fe and Ni. The spin texture is largely collinear deep inside the probes, but is complicated after boundary scattering. The calculated AHE resistance satisfies an Onsager-like symmetry relation.

We provide a potential solution to the longstanding problem relating Fermi surface reconstruction to the number of holes contained within the Fermi surface volume in underdoped high $T_{\mathrm{c}}$ superconductors. On considering uniaxial and biaxial charge-density wave order, we show that there exists a relationship between the ordering wave vector, the hole doping, and the cross-sectional area of the reconstructed Fermi surface whose precise form depends on the volume of the starting Fermi surface. We consider a “large” starting Fermi surface comprising $1+p$ hole carriers, as predicted by band structure calculations, and a “small” starting Fermi surface comprising $p$ hole carriers, as proposed in models in which the Coulomb repulsion remains the dominant energy. Using the reconstructed Fermi surface cross-sectional area obtained in quantum oscillation experiments in ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{6+x}$ and ${\mathrm{HgBa}}_2{\mathrm{CuO}}_{4+x}$ and the established methods for estimating the chemical hole doping, we find the ordering vectors obtained from x-ray scattering measurements to show a close correspondence with those expected for the small starting Fermi surface. We therefore show the quantum oscillation frequency and charge-density wave vectors provide accurate estimates for the number of holes contributing to the Fermi surface volume in the pseudogap regime.

We study braiding statistics between quasiparticles and vortices in two-dimensional charge-$2m$ (in units of $e$) superconductors that are coupled to a ${\mathbb{Z}}_{2m}$ dynamical gauge field, where $m$ is any positive integer. We show that there exist $16m$ types of braiding statistics when $m$ is odd, but only $4m$ types when $m$ is even. Based on the braiding statistics, we obtain a classification of topological phases of charge-$2m$ superconductors—or formally speaking, a classification of symmetry-protected topological phases, as well as invertible topological phases, of two-dimensional gapped fermions with ${\mathbb{Z}}_{2m}^f$ symmetry. Interestingly, we find that there is no nontrivial fermionic symmetry-protected topological phase with ${\mathbb{Z}}_4^f$ symmetry.

We perform ab initio calculations of the coupling between electrons and small-momentum polar-optical phonons in monolayer transition-metal dichalcogenides of the $2H$ type: ${\mathrm{MoS}}_2,{\mathrm{MoSe}}_2,{\mathrm{MoTe}}_2,{\mathrm{WS}}_2$, and ${\mathrm{WSe}}_2$. The polar-optical coupling with longitudinal optical phonons, or Fröhlich interaction, is fundamentally affected by the dimensionality of the system. In a plane-wave framework with periodic boundary conditions, the Fröhlich interaction is affected by the spurious interaction between the two-dimensional (2D) material and its periodic images. To overcome this difficulty, we perform density functional perturbation theory calculations with a truncated Coulomb interaction in the direction perpendicular to the plane of the 2D material. We show that the two-dimensional Fröhlich interaction is much stronger than assumed in previous ab initio studies. We provide analytical models depending on the effective charges and dielectric properties of the materials to interpret our ab initio calculations. Screening is shown to play a fundamental role in the phonon-momentum dependency of the polar-optical coupling, with a crossover between two regimes depending on the dielectric properties of the material relative to its environment. The Fröhlich interaction is screened by the dielectric environment in the limit of small phonon momenta and sharply decreases due to stronger screening by the monolayer at finite momenta. The small-momentum regime of the ab initio Fröhlich interaction is reproduced by a simple analytical model, for which we provide the necessary parameters. At larger momenta, however, direct ab initio calculations of electron-phonon interactions are necessary to capture band-specific effects. We compute and compare the carrier relaxation times associated with the scattering by both LO and $A_1$ phonon modes. While both modes are capable of relaxing carriers on time scales under the picosecond at room temperature, their absolute importance and relative importance vary strongly depending on the material, the band, and the substrate.

We study a system of particles in two dimensions interacting via a dipolar long-range potential $D/r^3$ and subject to a square-lattice substrate potential $V\left(\mathbf{r}\right)$ with amplitude $V$ and lattice constant $b$. The isotropic interaction favors a hexagonal arrangement of the particles with lattice constant $a$, which competes against the square symmetry of the underlying substrate lattice. We determine the minimal-energy states at fixed external pressure $p$ generating the commensurate density $n=1/b^2={(4/3)}^{1/2}/a^2$ in the absence of thermal and quantum fluctuations, using both analytical techniques based on the harmonic and continuum elastic approximations as well as numerical relaxation of particle configurations. At large substrate amplitude $V>0.2e_D$, with $e_D=D/b^3$ the dipolar energy scale, the particles reside in the substrate minima and hence arrange in a square lattice. Upon decreasing $V$, the square lattice turns unstable with respect to a zone-boundary shear mode and deforms into a period-doubled zigzag lattice. Analytic and numerical results show that this period-doubled phase in turn becomes unstable at $V\approx 0.074e_D$ towards a nonuniform phase developing an array of domain walls or solitons; as the density of solitons increases, the particle arrangement approaches that of a rhombic (or isosceles triangular) lattice. At a yet smaller substrate value estimated as $V\approx 0.046e_D$, a further solitonic transition establishes a second nonuniform phase which smoothly approaches the hexagonal (or equilateral triangular) lattice phase with vanishing amplitude $V$. At small but finite amplitude $V$, the hexagonal phase is distorted and hexatically locked at an angle of $\phi \approx 3.8^{\circ }$ with respect to the substrate lattice. The square-to-hexagonal transformation in this two-dimensional commensurate-incommensurate system thus involves a complex pathway with various nontrivial lattice- and modulated phases.

We present a theoretical scheme to calculate the elastic constants of magnetic materials in the high-temperature paramagnetic state. Our approach is based on a combination of disordered local moments picture and ab initio molecular dynamics (DLM-MD). Moreover, we investigate a possibility to enhance the efficiency of the simulations of elastic properties using the recently introduced method: symmetry imposed force constant temperature-dependent effective potential (SIFC-TDEP). We have chosen cubic paramagnetic CrN as a model system. This is done due to its technological importance and its demonstrated strong coupling between magnetic and lattice degrees of freedom. We have studied the temperature-dependent single-crystal and polycrystalline elastic constants of paramagentic CrN up to 1200 K. The obtained results at T = 300 K agree well with the experimental values of polycrystalline elastic constants as well as the Poisson ratio at room temperature. We observe that the Young's modulus is strongly dependent on temperature, decreasing by $\sim 14\%$ from T = 300 K to 1200 K. In addition we have studied the elastic anisotropy of CrN as a function of temperature and we observe that CrN becomes substantially more isotropic as the temperature increases. We demonstrate that the use of Birch law may lead to substantial errors for calculations of temperature induced changes of elastic moduli. The proposed methodology can be used for accurate predictions of mechanical properties of magnetic materials at temperatures above their magnetic order-disorder phase transition.

The magnetic anisotropies of a patterned, exchange biased ${\mathrm{Fe}}_{50}{\mathrm{Mn}}_{50}\text{/}{\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ system are studied using ferromagnetic resonance, supplemented by Brillouin light scattering experiments and Kerr magnetometry. The exchange biased bilayer is partially etched into an antidot geometry so that the system approximates a ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ layer in contact with antidot structured ${\mathrm{Fe}}_{50}{\mathrm{Mn}}_{50}$. Brillouin light scattering measurements of the spin wave frequency dependence on the wave vector reveal a magnonic band gap as expected for a periodic modulation of the magnetic properties. Analysis of the ferromagnetic resonance spectra reveals eightfold and fourfold contributions to the magnetic anisotropy. Additionally, the antidot patterning decreases the magnitude of the exchange bias and modifies strongly its angular dependence. Softening of all resonance modes is most pronounced for the applied magnetic field aligned within ${10}^{\circ }$ of the antidot axis, in the direction of the bias. Given the degree to which one can tailor the ground state, the resulting asymmetry at low frequencies could make this an interesting candidate for applications such as selective/directional microwave filtering and multistate magnetic logic.

We consider a two-component Bose-Einstein condensate with and without synthetic “spin-orbit” interactions in two dimensions. Density and phase fluctuations of the condensate are included, allowing us to study the impact of thermal fluctuations and density-density interactions on the physics originating with spin-orbit interactions. In the absence of spin-orbit interactions, we find that intercomponent density interactions deplete the minority condensate. The thermally driven phase transition is driven by coupled density and phase-fluctuations, but is nevertheless shown to be a phase-transition in the Kosterlitz-Thouless universality class with close to universal amplitude ratios irrespective of whether both the minority- and majority condensates exist in the ground state, or only one condensate exists. In the presence of spin-orbit interactions we observe three separate phases, depending on the strength of the spin-orbit coupling and intercomponent density-density interactions: a phase-modulated phase with uniform amplitudes for small intercomponent interactions, a completely imbalanced, effectively single-component condensate for intermediate spin-orbit coupling strength and sufficiently large intercomponent interactions, and a phase-modulated and amplitude-modulated phase for sufficiently large values of both the spin-orbit coupling and the intercomponent density-density interactions. The phase that is modulated by a single $\mathit{q}$-vector only is observed to transition into an isotropic liquid through a strong depinning transition with periodic boundary conditions, which weakens with open boundaries.

The Bogomolnyi point separates superconductivity types I and II while itself hiding infinitely degenerate magnetic flux configurations, including very exotic states (referred to here as flux “monsters”). When the degeneracy is removed, the Bogomolnyi point unfolds into a finite, intertype domain in the phase diagram between types I and II. One can expect that in this case the flux monsters can escape their “prison” at the Bogomolnyi point, occupying the intertype domain and shaping its internal structure. Our calculations reveal that such exotic flux distributions are indeed stable in the intertype regime of thin superconductors made of a type-I material, where the Bogomolnyi degeneracy is removed by stray magnetic fields. They can be classified into three typical patterns that are qualitatively different from those in types I and II: superconducting islands separated by vortex chains; stripes/worms/labyrinths patterns; and mixtures of giant vortices and vortex clusters. Our findings shed light on the problem of the interchange between types I and II, raising important questions on the completeness of the textbook classification of the superconductivity types.

We report on the six-dimensional (6D) structural refinement of three members of the i-$R$-Cd quasicrystals ($R$ = Gd, Dy, Tm) via synchrotron x-ray diffraction from single-grain samples, and show that this series is isostructural to the i-${\mathrm{YbCd}}_{5.7}$ quasicrystal. However, our refinements suggest that the $R$ occupancy on the Yb icosahedron sites within the Tsai-type atomic cluster is approximately 80%, with the balance taken up by Cd. Similarities between the i-$R$-Cd series and i-${\mathrm{ScZn}}_{7.33}$, and their differences with i-${\mathrm{YbCd}}_{5.7}$ and i-${\mathrm{Ca}}_{15}{\mathrm{Cd}}_{85}$, indicate that there are at least two subclasses of Tsai-type icosahedral quasicrystals. We further show from x-ray resonant magnetic scattering (XRMS) measurements on a set of closely related ${\mathrm{Tb}}_{1-x}{\mathrm{Y}}_x{\mathrm{Cd}}_6$ 1/1 approximants that the dilution of the magnetic $R$ ions on the icosahedron within the Tsai-type cluster by nonmagnetic Y disrupts the commensurate magnetic ordering in the approximant phase.

Below $T_N=1.1$ K, the $XY$ pyrochlore ${\mathrm{Er}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ orders into a $k=0$ noncollinear, antiferromagnetic structure referred to as the ${\psi }_2$ state. The magnetic order in ${\mathrm{Er}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ is known to obey conventional three-dimensional (3D) percolation in the presence of magnetic dilution, and in that sense is robust to disorder. Recently, however, two theoretical studies have predicted that the ${\psi }_2$ structure should be unstable to the formation of a related ${\psi }_3$ magnetic structure in the presence of magnetic vacancies. To investigate these theories, we have carried out systematic elastic and inelastic neutron scattering studies of three single crystals of ${\mathrm{Er}}_{2-x}{\mathrm{Y}}_x{\mathrm{Ti}}_2{\mathrm{O}}_7$ with $x=0$ (pure), $0.2 \left(10\%\mathrm{Y}\right)$ and 0.4 ($20\% \mathrm{Y}$), where magnetic ${\mathrm{Er}}^{3+}$ is substituted by nonmagnetic ${\mathrm{Y}}^{3+}$. We find that the ${\psi }_2$ ground state of pure ${\mathrm{Er}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ is significantly affected by magnetic dilution. The characteristic domain selection associated with the ${\psi }_2$ state, and the corresponding energy gap separating ${\psi }_2$ from ${\psi }_3$, vanish for ${\mathrm{Y}}^{3+}$ substitutions between $10\% \mathrm{Y}$ and $20\% \mathrm{Y}$, far removed from the three-dimensional percolation threshold of $\sim 60\% \mathrm{Y}$. The resulting ground state for ${\mathrm{Er}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ with magnetic dilutions from $20\% \mathrm{Y}$ up to the percolation threshold is naturally interpreted as a frozen mosaic of ${\psi }_2$ and ${\psi }_3$ domains.

The hyperkagome iridate, ${\mathrm{Na}}_4{\mathrm{Ir}}_3{\mathrm{O}}_8$, has been regarded as a promising candidate material for a three-dimensional quantum spin liquid. Here the three-dimensional network of corner-sharing triangles forms the hyperkagome lattice of ${\mathrm{Ir}}^{4+}$ ions. Due to strong spin-orbit coupling, the local moments of ${\mathrm{Ir}}^{4+}$ ions are described by the pseudospin $j_{\mathrm{eff}}=1/2$ Kramers doublet. The Heisenberg model on this lattice is highly frustrated, and quantum/classical versions have been studied in earlier literature. In this work, we derive a generic local-moment model beyond the Heisenberg limit for the hyperkagome iridate by considering multiorbital interactions for all the $t_{2g}$ orbitals and spin-orbit coupling. The lifting of massive classical degeneracy in the Heisenberg model by various spin-anisotropy terms is investigated at the classical level, and the resulting phase diagram is presented. We find that different anisotropy terms prefer distinct classes of magnetically ordered phases, often with various discrete degeneracy. The implications of our results for recent $\mu \mathrm{SR}$ and NMR experiments on this material and possible quantum spin liquid phases are discussed.

This paper reports the investigation of the magnetic hyperfine field $B_{hf}$ in a series of rare-earth ($R$) cadmium intermetallic compounds $R\mathrm{Cd}$ and ${\mathrm{GdCd}}_2$ measured by perturbed angular correlation (PAC) spectroscopy using ${}^{111}\mathrm{In}/{}^{111}\mathrm{Cd}$ as probe nuclei at Cd sites as well as first-principles calculations of $B_{hf}$ at Cd sites in the studied compounds. Vapor–solid state reaction of $R$ metals with Cd vapor and the ${}^{111}\mathrm{In}$ radioisotope was found to be an appropriate route of doping rare-earth cadmium compounds with the PAC probe ${}^{111}\mathrm{In}/{}^{111}\mathrm{Cd}$. The observation that the hyperfine parameters depend on details of the sample preparation provides information on the phase preference of diffusing ${}^{111}\mathrm{In}$ in the rare-earth cadmium phase system. The ${}^{111}\mathrm{Cd}$ hyperfine field has been determined in the compounds $R\mathrm{Cd}$ for the $R$ constituents Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, and Er, in several cases as a function of temperature. For most $R$ constituents, the temperature dependence $B_{hf}\left(T\right)$ of ${}^{111}\mathrm{Cd}$:$R\mathrm{Cd}$ is consistent with ferromagnetic order of the compound. DyCd, however, presents a remarkable anomaly: a finite magnetic hyperfine field is observed only in the temperature interval 35 K $\le T \le$ 80 K which indicates a transition from ferromagnetic order to a spin arrangement where all $4f$-induced contributions to the magnetic hyperfine field at the Cd site cancel. First-principles calculation results for DyCd show that the ($\pi , \pi$, 0) antiferromagnetic configuration is energetically more favorable than the ferromagnetic. The approach used in the calculations to simulate the $R\mathrm{Cd}$ system successfully reproduces the experimental values of $B_{hf}$ at Cd sites and shows that the main contribution to $B_{hf}$ comes from the valence electron polarization. The de Gennes plot of the hyperfine field $B_{hf}$ of ${}^{111}\mathrm{Cd}$:$R\mathrm{Cd}$ vs the $4f$-spin projection $(g-1)J$ reflects a decrease of the strength of indirect $4f-4f$ exchange across the $R$ series. Possible mechanisms are discussed and the experimental results indicate that the indirect coupling is provided by the intra-atomic $4f-5d$ exchange and interatomic $5d-5d$ interaction between the spin-polarized $5d$ electrons of neighboring $R$ atoms. The ratio of the hyperfine fields of GdCd and ${\mathrm{GdCd}}_2$ scales with the number of nearest Gd neighbors. In the paramagnetic phases of the $R\mathrm{Cd}$ compounds, the PAC spectra indicate the presence of a broad distribution of weak quadrupole interactions suggesting a perturbation of the cubic CsCl symmetry of the Cd site, most probably due to chemical disorder of the $R$ and Cd sublattices. A substantial interchange of $R$ and Cd atoms is also reflected in the temperature dependence of the linewidth of the magnetic hyperfine interaction in the magnetically ordered phase of $R\mathrm{Cd}$ and ${\mathrm{GdCd}}_2$. Its critical increase towards the order temperature is evidence for a distribution of the order temperature with a width of about 10 K.

We present an investigation of the magnetic-field-temperature phase diagram of ${\mathrm{Cu}}_2{\mathrm{OSeO}}_3$ based on dc magnetization and ac susceptibility measurements covering a broad frequency range of four orders of magnitude, from very low frequencies reaching 0.1 Hz up to 1 kHz. The experiments were performed in the vicinity of $T_c=58.2$ K and around the skyrmion lattice $A$ phase. At the borders between the different phases the characteristic relaxation times reach several milliseconds and the relaxation is nonexponential. Consequently the borders between the different phases depend on the specific criteria and frequency used and an unambiguous determination is not possible.

To understand the necessary condition for the observation of all-optical helicity-dependent switching (AO-HDS) of magnetization in thin films, we investigated ferromagnetic Co/Pt and Co/Ni multilayers as well as ferrimagnetic TbCo alloys as a function of magnetic layer compositions and thicknesses. We show that both ferro- and ferrimagnets with high saturation magnetization show AO-HDS if their magnetic thickness is strongly reduced below a material-dependent threshold thickness. By taking into account the demagnetizing energy and the domain wall energy, we are able to define a criterion to predict whether AO-HDS or thermal demagnetization (TD) will be observed. This criterion for the observation of AO-HDS is that the equilibrium size of magnetic domains forming during the cooling process should be larger than the laser spot size. From these results we anticipate that more magnetic materials are expected to show AO-HDS. However, the effect of the optical pulses' helicity is hidden by the formation of small magnetic domains during the cooling process.

We report the occurrence of a magnetodielectric effect and its correlation with structure and magnetism in the $A$-site ordered chromate spinel oxides $\mathrm{Li}M\mathrm{C}{\mathrm{r}}_4{\mathrm{O}}_8$ ($M=\mathrm{Ga}$, In). In addition to magnetic and dielectric measurements, temperature dependent synchrotron and neutron diffraction experiments have been carried out for the Ga compound. The results are compared and contrasted with that of a corresponding conventional $B$-site magnetic chromate spinel oxide, $\mathrm{ZnC}{\mathrm{r}}_2{\mathrm{O}}_4$. Like $\mathrm{ZnC}{\mathrm{r}}_2{\mathrm{O}}_4$, the $A$-site ordered chromate spinels exhibit a magnetodielectric effect at the magnetic ordering temperature ($T_{\mathrm{N}}\sim 13–15\mathrm{K}$), resulting from magnetoelastic coupling through a spin Jahn-Teller effect. While the presence of a broad magnetic anomaly, associated with a short-range magnetic ordering ($T_{\mathrm{SO}}\sim 45\mathrm{K}$) in $\mathrm{ZnC}{\mathrm{r}}_2{\mathrm{O}}_4$, does not cause any dielectric anomaly, a sharp change in dielectric constant has been observed in $\mathrm{LiInC}{\mathrm{r}}_4{\mathrm{O}}_8$ at the magnetic anomaly, which is associated with the opening of a spin gap ($T_{\mathrm{SG}}\sim 60\mathrm{K}$). Contrary to the In compound, a broad dielectric anomaly exists at the onset of short-range antiferromagnetic ordering ($T_{\mathrm{SO}}\sim 55\mathrm{K}$) in $\mathrm{LiGaC}{\mathrm{r}}_4{\mathrm{O}}_8$. The differences in dielectric behavior of these compounds have been discussed in terms of breathing distortion of the $\mathrm{C}{\mathrm{r}}_4$ tetrahedra.

We consider finite-time quantum quenches in the interacting Tomonaga-Luttinger model, for example time-dependent changes of the nearest-neighbor interactions for spinless fermions. We use the exact solutions for specific protocols including the linear and cosine ramps (or, more generally, periodic pumping). We study the dynamics of the total and kinetic energy as well as the Green's functions during as well as after the quench. For the latter we find that the light-cone picture remains applicable; however, the propagating front is delayed as compared to the sudden quench. We extract the universal behavior of the Green's functions and in particular provide analytic, nonperturbative results for the delay applicable to quenches of short to moderate duration but arbitrary time dependency.

By using Gutzwiller projected fermionic wave functions and variational Monte Carlo technique, we study the spin-$1/2$ Heisenberg model with the first-neighbor ($J_1$), second-neighbor ($J_2$), and additional scalar chiral interaction $J_{\chi }{\mathbf{S}}_i·({\mathbf{S}}_j\times {\mathbf{S}}_k)$ on the triangular lattice. In the nonmagnetic phase of the $J_1-J_2$ triangular model with $0.08\lesssim J_2/J_1\lesssim 0.16$, recent density-matrix renormalization group (DMRG) studies [Zhu and White, Phys. Rev. B 92, 041105(R) (2015) and Hu, Gong, Zhu, and Sheng, Phys. Rev. B 92, 140403(R) (2015)] find a possible gapped spin liquid with the signal of a competition between a chiral and a $Z_2$ spin liquid. Motivated by the DMRG results, we consider the chiral interaction $J_{\chi }{\mathbf{S}}_i·({\mathbf{S}}_j\times {\mathbf{S}}_k)$ as a perturbation for this nonmagnetic phase. We find that with growing $J_{\chi }$, the gapless U(1) Dirac spin liquid, which has the best variational energy for $J_{\chi }=0$, exhibits the energy instability towards a gapped spin liquid with nontrivial magnetic fluxes and nonzero chiral order. We calculate topological Chern number and ground-state degeneracy, both of which identify this flux state as the chiral spin liquid with fractionalized Chern number $C=1/2$ and twofold topological degeneracy. Our results indicate a positive direction to stabilize a chiral spin liquid near the nonmagnetic phase of the $J_1-J_2$ triangular model.

Acceptor-doped perovskite oxides like ${\text{BaZrO}}_3$ are showing great potential as materials for renewable energy technologies where hydrogen acts an energy carrier, such as solid oxide fuel cells and hydrogen separation membranes. While ionic transport in these materials has been investigated intensively, the electronic counterpart has received much less attention and further exploration in this field is required. Here, we use density functional theory (DFT) to study hole polarons and their impact on hole conductivity in Y-doped ${\text{BaZrO}}_3$. Three different approaches have been used to remedy the self-interaction error of local and semilocal exchange-correlation functionals: $\mathrm{DFT}+U$, pSIC-DFT, and hybrid functionals. Self-trapped holes are found to be energetically favorable by about $-0.1$ eV and the presence of yttrium results in further stabilization. Polaron migration is predicted to occur through intraoctahedral transfer and polaron rotational processes, which are associated with adiabatic barriers of about 0.1 eV. However, the rather small energies associated with polaron formation and migration suggest that the hole becomes delocalized and bandlike at elevated temperatures. These results together with an endothermic oxidation reaction [A. Lindman, P. Erhart, and G. Wahnström, Phys. Rev. B 91, 245114 (2015)] yield a picture that is consistent with experimental data for the hole conductivity. The results we present here provide new insight into hole transport in acceptor-doped ${\text{BaZrO}}_3$ and similar materials, which will be of value in the future development of sustainable technologies.