Theory of Polar Corrections to Donor Binding

We calculate the optical phonon correction to the binding energy of electrons to donors in cubic materials. Previous theories calculated the Rydberg energy reduced by the effective mass and the static dielectric function. They omitted an important energy term from the long-range polarization of the ionized donor, which vanishes for the neutral donor. They also omitted the donor-phonon interaction. Including these terms yields a new formula for the donor binding energy

Orbital Polarization in Itinerant Magnets

We propose a parameter-free scheme of calculation of the orbital polarization (OP) in metals, which starts with the strong-coupling limit for the screened Coulomb interactions in the random-phase approximation (RPA). For itinerant magnets, RPA can be further improved by restoring the spin polarization of the local-spin-density approximation (LSDA) through the local-field corrections. The OP is then computed in the static GW approach, which systematically improves the orbital magnetization and the magnetic anisotropy energies in transition-metal and actinide compounds.Comment: 5 pages, 4 figure

Haldane Sashes in Quantum Hall Spectra

We show that the low-temperature sash features in the lowest Landau-level (LLL) tunneling density-of-states (TDOS) recently discovered by Dial and Ashoori are intimately related to the discrete Haldane-pseudopotential interaction energy scales that govern fractional quantum Hall physics. Our analysis is based on expressions for the tunneling density-of-states which become exact at filling factors close to $\nu=0$ and $\nu=1$, where the sash structure is most prominent. We comment on other aspects of LLL correlation physics that can be revealed by accurate temperature-dependent tunneling data.Comment: Added referenc

Induced spin texture in semiconductor/topological insulator heterostructures

We show that a semiconductor thin film can acquire a non-trivial spin texture due to the proximity effect induced by a topological insulator. The effect stems from coupling to the topological surface states and is present even when the insulator is doped. We propose a semiconductor/topological insulator heterostructure as a device that allows measuring interface properties and probing surface states in uncompensated samples. We also find that the topological insulator surface modes can be significantly broadened and shifted by the presence of metallic contacts.Comment: 6 pages, 2 figures, published versio

Giant anharmonicity suppresses superconductivity in AlH3_3 under pressure

The anharmonic self energy of two zone boundary phonons were computed to lowest order for AlH$_3$ in the $Pm\bar 3n$ structure at 110 GPa. The wavevector and branch index corresponding to these modes are situated in a region of phase space providing most of the electron-phonon coupling. The self energies are found to be very large and the anharmonic contribution to the linewidth of one of the modes studied could be distinguished from the electron-phonon linewidth. It is found that anharmonicity suppresses the electron-phonon coupling parameter $\lambda$, providing a possible explanation for the disagreement between experiment and previous theoretical studies of superconductivity in this system.Comment: 10 pages, 4 figure

Reply to Comment on "Critical analysis of a variational method used to describe molecular electron transport"

We show that the failure of the Delaney-Greer (DG) variational ansatz for transport demonstrated by us in Phys.\ Rev.\ B {\bf 80}, 165301 (2009) (I) is not related to an unsuitable constraint that prevents a broken time-reversal symmetry or to real orbitals, as DG incorrectly claim. The complex orbitals suggested by them as a way-out solution merely represent a particular case of the general case considered by us in I, which do not in the least affect our conclusion.Comment: Manuscript as submitted to Phys. Rev. B on 30 November 2010. Sections VII, VIII, and IX present significant details, which enlarge the analysis of the published versio

Electronic transport in ferromagnetic conductors with inhomogeneous magnetic order parameter -- domain-wall resistance

We microscopically derive transport equations for the conduction electrons in ferromagnetic materials with an inhomogeneous magnetization profile. Our quantum kinetic approach includes elastic scattering and anisotropic spin-flip scattering at magnetic impurities. In the diffusive limit, we calculate the resistance through a domain wall and find that the domain-wall resistance can be positive or negative. In the limit of long domain walls we derive analytical expressions and compare them with existing works, which used less general models or different theoretical frameworks.Comment: 19 Page

The thermopower as a fingerprint of the Kondo breakdown quantum critical point

We propose that the thermoelectric power distinguishes two competing scenarios for quantum phase transitions in heavy fermions : the spin-density-wave (SDW) theory and breakdown of the Kondo effect. In the Kondo breakdown scenario, the Seebeck coefficient turns out to collapse from the temperature scale $E^{*}$, associated with quantum fluctuations of the Fermi surface reconfiguration. This feature differs radically from the physics of the SDW theory, where no reconstruction of the Fermi surface occurs, and can be considered as the hallmark of the Kondo breakdown theory. We test these ideas, upon experimental results for YbRh$_2$Si$_2$

Green's function of a dressed particle

We present a new, highly efficient yet accurate approximation for the Green's functions of dressed particles, using the Holstein polaron as an example. Instead of summing a subclass of diagrams (e.g. the non-crossed ones, in the self-consistent Born approximation (SCBA)), we sum all the diagrams, but with each diagram averaged over its free propagators' momenta. The resulting Green's function satisfies exactly the first six spectral weight sum rules. All higher sum rules are satisfied with great accuracy, becoming asymptotically exact for coupling both much larger and much smaller than the free particle bandwidth. Possible generalizations to other models are also discussed.Comment: 4 pages, 3 figure