Rufus Boyack
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View article: Upper bound on <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>c</mml:mi> </mml:msub> </mml:math> in a strongly coupled electron-boson superconductor
Upper bound on in a strongly coupled electron-boson superconductor Open
Migdal-Eliashberg theory of boson-mediated superconductivity contains a $\sqrtλ$ divergence in the critical temperature $T_c$ for strong electron-boson coupling $λ$. In the conventional Migdal-Eliashberg theory, the strong-coupling regime …
View article: Anomalous Superfluid Density in Pair-Density-Wave Superconductors
Anomalous Superfluid Density in Pair-Density-Wave Superconductors Open
Pair-density-wave (PDW) states are a long-sought-after phase of quantum materials, with the potential to unravel the mysteries of high-$T_c$ cuprates and other strongly correlated superconductors. Yet, surprisingly, a key signature of stab…
View article: Universal Scaling Relations in Electron-Phonon Superconductors
Universal Scaling Relations in Electron-Phonon Superconductors Open
We study linear scaling relations in electron-phonon superconductors. By combining numerical and analytical techniques, we find linear Homes scaling relations between the zero-temperature superfluid density and the normal-state DC conducti…
View article: The Higgs-Amplitude mode in the optical conductivity in the presence of a supercurrent: Gauge-invariant formulation with disorder
The Higgs-Amplitude mode in the optical conductivity in the presence of a supercurrent: Gauge-invariant formulation with disorder Open
Observing the ``Higgs" or amplitude mode in superconductors has been a central challenge in condensed matter physics. Moreover, arriving at a theoretical understanding of this mode and how it is accessible in, say, conductivity experiments…
View article: Conformal field theories in a magnetic field
Conformal field theories in a magnetic field Open
We study the properties of 2+1d conformal field theories (CFTs) in a background magnetic field. Using generalized particle-vortex duality, we argue that in many cases of interest the theory becomes gapped, which allows us to make a number …
View article: When superconductivity crosses over: From BCS to BEC
When superconductivity crosses over: From BCS to BEC Open
The theory of unconventional superconductors continues to provide profound puzzles. The crossover between the weakly coupled Bardeen-Cooper-Schrieffer (BCS) state and the strong-pairing Bose-Einstein condensate (BEC) provides a useful pers…
View article: Test for BCS-BEC crossover in the cuprate superconductors
Test for BCS-BEC crossover in the cuprate superconductors Open
In this paper we address the question of whether high-temperature superconductors have anything in common with BCS-BEC crossover theory. Towards this goal, we present a proposal and related predictions which provide a concrete test for the…
View article: Conformal field theories in a magnetic field
Conformal field theories in a magnetic field Open
We study the properties of 2+1d conformal field theories (CFTs) in a background magnetic field. Using generalized particle-vortex duality, we argue that in many cases of interest the theory becomes gapped, which allows us to make a number …
View article: Test for BCS-BEC Crossover in the Cuprate Superconductors
Test for BCS-BEC Crossover in the Cuprate Superconductors Open
In this paper we address the question of whether high-temperature superconductors have anything in common with BCS-BEC crossover theory. Towards this goal, we present a proposal and related predictions which provide a concrete test for the…
View article: Electrical conductivity and nuclear magnetic resonance relaxation rate of Eliashberg superconductors in the weak-coupling limit
Electrical conductivity and nuclear magnetic resonance relaxation rate of Eliashberg superconductors in the weak-coupling limit Open
Electrical conductivity is an important transport response in superconductors, enabling clear signatures of dynamical interactions to be observed. Of primary interest in this paper is to study characteristics of the electron-phonon interac…
View article: Binet's second formula, Hermite's generalization, and two related identities
Binet's second formula, Hermite's generalization, and two related identities Open
Legendre was the first to evaluate two well-known integrals involving sines and exponentials. One of these integrals can be used to prove Binet’s second formula for the logarithm of the gamma function. Here, we show that the other integral…
View article: Electrical conductivity and nuclear magnetic resonance relaxation rate of Eliashberg superconductors in the weak-coupling limit
Electrical conductivity and nuclear magnetic resonance relaxation rate of Eliashberg superconductors in the weak-coupling limit Open
Electrical conductivity is an important transport response in superconductors, enabling clear signatures of dynamical interactions to be observed. Of primary interest in this paper is to study characteristics of the electron-phonon interac…
View article: When Superconductivity Crosses Over: From BCS to BEC
When Superconductivity Crosses Over: From BCS to BEC Open
New developments in superconductivity, particularly through unexpected and often astonishing forms of superconducting materials, continue to excite the community and stimulate theory. It is now becoming clear that there are two distinct pl…
View article: Anomalous Dimensions of Monopole Operators at the Transitions between Dirac and Topological Spin Liquids
Anomalous Dimensions of Monopole Operators at the Transitions between Dirac and Topological Spin Liquids Open
Monopole operators are studied in a large family of quantum critical points\nbetween Dirac and topological quantum spin liquids (QSLs): chiral and Z$_{2}$\nQSLs. These quantum phase transitions are described by conformal field theories\n(C…
View article: Heat-bath approach to anomalous thermal transport: Effects of inelastic scattering
Heat-bath approach to anomalous thermal transport: Effects of inelastic scattering Open
We present results for the entire set of anomalous charge and heat transport\ncoefficients for metallic systems in the presence of a finite-temperature heat\nbath. In realistic physical systems this necessitates the inclusion of\ninelastic…
View article: The bound-state solutions of the one-dimensional pseudoharmonic oscillator
The bound-state solutions of the one-dimensional pseudoharmonic oscillator Open
We study the bound states of a quantum mechanical system consisting of a simple harmonic oscillator with an inverse square interaction, whose interaction strength is governed by a constant $α$. The singular form of this potential has doubl…
View article: Anomalous dimensions of monopole operators at the transitions between Dirac and topological spin liquids
Anomalous dimensions of monopole operators at the transitions between Dirac and topological spin liquids Open
Monopole operators are studied in a large family of quantum critical points between Dirac and topological quantum spin liquids (QSLs): chiral and Z$_{2}$ QSLs. These quantum phase transitions are described by conformal field theories (CFTs…
View article: Functional-integral approach to Gaussian fluctuations in Eliashberg theory
Functional-integral approach to Gaussian fluctuations in Eliashberg theory Open
The Eliashberg theory of superconductivity is based on a dynamical electron-phonon interaction as opposed to a static interaction present in BCS theory. The standard derivation of Eliashberg theory is based on an equation of motion approac…
View article: Triangular pair density wave in confined superfluid $^3$He
Triangular pair density wave in confined superfluid $^3$He Open
Recent advances in experiment and theory suggest that superfluid $^3$He under planar confinement may form a pair density wave (PDW) whereby superfluid and crystalline orders coexist. While a natural candidate for this phase is a unidirecti…
View article: The bound-state solutions of the one-dimensional hydrogen atom
The bound-state solutions of the one-dimensional hydrogen atom Open
The one-dimensional hydrogen atom is an intriguing quantum mechanics problem that exhibits several properties which have been continually debated. In particular, there has been variance as to whether or not even-parity solutions exist, and…
View article: Thermodynamics of Eliashberg theory in the weak-coupling limit
Thermodynamics of Eliashberg theory in the weak-coupling limit Open
The weak-coupling limits of the gap and critical temperature computed within Eliashberg theory surprisingly deviate from the BCS theory predictions by a factor of $1/\sqrt{e}$. Interestingly, however, the ratio of these two quantities agre…
View article: Critical properties of the valence-bond-solid transition in lattice quantum electrodynamics
Critical properties of the valence-bond-solid transition in lattice quantum electrodynamics Open
Elucidating the phase diagram of lattice gauge theories with fermionic matter in 2+1 dimensions has become a problem of considerable interest in recent years, motivated by physical problems ranging from chiral symmetry breaking in high-ene…
View article: Electromagnetic response of superconductors in the presence of multiple collective modes
Electromagnetic response of superconductors in the presence of multiple collective modes Open
We revisit the importance of collective-mode fluctuations and gauge\ninvariance in the electromagnetic response of superconducting systems. In\nparticular, we show that order-parameter fluctuations, gapless or not, have no\ncontribution to…
View article: Eliashberg theory in the weak-coupling limit: Results on the real frequency axis
Eliashberg theory in the weak-coupling limit: Results on the real frequency axis Open
We formulate and solve the Eliashberg equations on the imaginary frequency axis at temperatures below $T_c$ in the weak-coupling limit. We find an excellent scaling at all temperatures, for a given coupling strength, and the normalized ord…
View article: Critical properties of the Néel–algebraic-spin-liquid transition
Critical properties of the Néel–algebraic-spin-liquid transition Open
The algebraic spin liquid is a long-sought-after phase of matter characterized by the absence of quasiparticle excitations, a low-energy description in terms of emergent Dirac fermions and gauge fields interacting according to (2+1)D quant…
View article: Combined effects of pairing fluctuations and a pseudogap in the cuprate Hall coefficient
Combined effects of pairing fluctuations and a pseudogap in the cuprate Hall coefficient Open
The normal-state behavior of the temperature-dependent Hall coefficient in\ncuprate superconductors is investigated using linear response theory. The Hall\nconductivity is of paramount importance in that its sign and magnitude directly\nre…
View article: Restoring gauge invariance in conventional fluctuation corrections to a superconductor
Restoring gauge invariance in conventional fluctuation corrections to a superconductor Open
The complete set of diagrams for conventional fluctuation corrections to the normal state of an ultraclean superconductor is derived using the functional-integral approach. The standard diagrams which characterize the fluctuation phase of …