# SIMES Publications

Enter search terms and sorting preferences below:

**"Disruption of quantum oscillations by an incommensurate charge density wave"** — Yi Zhang: Akash V. Maharaj, and Steven Kivelson; Phys. Rev. B 91, 02/09/2015.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Akash V. Maharaj, and Steven Kivelson

**Abstract**

Because a material with an incommensurate charge density wave (ICDW) is only quasiperiodic, Bloch’s theorem does not apply and there is no sharply defined Fermi surface. We will show that, as a consequence, there are no quantum oscillations which are truly periodic functions of 1/*B* (where *B* is the magnitude of an applied magnetic field). For a weak ICDW, there exist broad ranges of 1/*B* in which approximately periodic variations occur, but with frequencies that vary inexorably in an unending cascade with increasing 1/*B* . For a strong ICDW, e.g., in a quasicrystal, no quantum oscillations survive at all. Rational and irrational numbers really are different.

**"Transverse fields to tune an Ising-nematic quantum phase transition"** — Akash V. Maharaj: Elliott W. Rosenberg, Alexander T. Hristov, Erez Berg, Rafael M. Fernandes, Ian R. Fisher and Steven A. Kivelson; Proceedings of the National Academy of Sciences, 12/05/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Elliott W. Rosenberg, Alexander T. Hristov, Erez Berg, Rafael M. Fernandes, Ian R. Fisher and Steven A. Kivelson

**Abstract**

The paradigmatic example of a continuous quantum phase transition is the transverse field Ising ferromagnet. In contrast to classical critical systems, whose properties depend only on symmetry and the dimension of space, the nature of a quantum phase transition also depends on the dynamics. In the transverse field Ising model, the order parameter is not conserved, and increasing the transverse field enhances quantum fluctuations until they become strong enough to restore the symmetry of the ground state. Ising pseudospins can represent the order parameter of any system with a twofold degenerate broken-symmetry phase, including electronic nematic order associated with spontaneous point-group symmetry breaking. Here, we show for the representative example of orbital-nematic ordering of a non-Kramers doublet that an orthogonal strain or a perpendicular magnetic field plays the role of the transverse field, thereby providing a practical route for tuning appropriate materials to a quantum critical point. While the transverse fields are conjugate to seemingly unrelated order parameters, their nontrivial commutation relations with the nematic order parameter, which can be represented by a Berry-phase term in an effective field theory, intrinsically intertwine the different order parameters.

**"Critical divergence of the symmetric (A**_{1g}) nonlinear elastoresistance near the nematic transition in an iron-based superconductor" — J. C. Palmstrom: A. T. Hristov, S. A. Kivelson, J.-H. Chu, and I. R. Fisher; Physical Review B, 11/17/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

A. T. Hristov, S. A. Kivelson, J.-H. Chu, and I. R. Fisher

**Abstract**

We report the observation of a nonlinear elastoresistivity response for the prototypical underdoped iron pnictide Ba(Fe_{0.975}Co_{0.025})_{2}As_{2}. Our measurements reveal a large quadratic term in the isotropic (A_{1}_{g}) electronic response that was produced by a purely shear (B_{2}_{g}) strain. The divergence of this quantity upon cooling towards the structural phase transition reflects the temperature dependence of the nematic susceptibility. This observation shows that nematic fluctuations play a significant role in determining even the isotropic properties of this family of compounds.

**"Fractional charge and emergent mass hierarchy in diagonal two-leg*** t-J *cylinders" — Yi-Fan Jiang: Hong-Chen Jiang, Hong Yao, and Steven A. Kivelson; Physical Review B, 09/25/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Hong-Chen Jiang, Hong Yao, and Steven A. Kivelson

**Abstract**

We define a class of “diagonal” *t**–**J* ladders rotated by π/4 relative to the canonical lattice directions of the square lattice, and study it using density matrix renormalization group. Here, we focus on the two-leg cylinder with a doped hole concentration near *x*=1/4. At exactly *x*=1/4, the system forms a period 4 charge density wave and exhibits spin-charge separation. Slightly away from 1/4 doping, we observe several topologically distinct types of solitons with well-defined fractionalized quantum numbers. Remarkably, given the absence of any obvious small parameter, the effective masses of the emergent solitons differ by several orders of magnitude.

**"Vestigial nematicity from spin and/or charge order in the cuprates"** — Laimei Nie: Akash V. Maharaj, Eduardo Fradkin, and Steven A. Kivelson; Physical Review B, 08/28/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Akash V. Maharaj, Eduardo Fradkin, and Steven A. Kivelson

**Abstract**

Nematic order has manifested itself in a variety of materials in the cuprate family. We propose an effective field theory of a layered system with incommensurate, intertwined spin- and charge-density wave (SDW and CDW) orders, each of which consists of two components related by C_{4} rotations. Using a variational method (which is exact in a large-*N* limit), we study the development of nematicity from partially melting those density waves by either increasing temperature or adding quenched disorder. As temperature decreases we first find a transition to a *single* nematic phase, but depending on the range of parameters (e.g., doping concentration) the strongest fluctuations associated with this phase reflect either proximate SDW or CDW order. We also discuss the changes in parameters that can account for the differences in the SDW-CDW interplay between the 214 family and the other hole-doped cuprates.

**"Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid"** — Hong-Chen Jiang: Devereaux, T., Kivelson, S.A.; Phys Rev Lett, 08/07/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Devereaux, T., Kivelson, S.A.

**Abstract**

We address the problem of a lightly doped spin liquid through a large-scale density-matrix renormalization group study of the* **t−J* model on a kagome lattice with a small but nonzero concentration* **δ* of doped holes. It is now widely accepted that the undoped (*δ*=0) spin-1/2 Heisenberg antiferromagnet has a spin-liquid ground state. Theoretical arguments have been presented that light doping of such a spin liquid could give rise to a high temperature superconductor or an exotic topological Fermi liquid metal. Instead, we infer that the doped holes form an insulating charge-density wave state with one doped hole per unit cell, i.e., a Wigner crystal. Spin correlations remain short ranged, as in the spin-liquid parent state, from which we infer that the state is a crystal of spinless holons, rather than of holes. Our results may be relevant to kagome lattice herbertsmithite upon doping.

**"Dispersive charge density wave excitations in Bi**_{2}Sr_{2}CaCu_{2}O_{8+δ}" — L. Chaix: G. Ghiringhelli, Y. Y. Peng, M. Hashimoto, B. Moritz, K. Kummer, N. B. Brookes, Y. He, S. Chen, S. Ishida, Y. Yoshida, H. Eisaki, M. Salluzzo, L. Braicovich, Z.-X. Shen, T. P. Devereaux & W.-S. Lee; Nature Physics, 06/12/17.

Show Abstract » | Show Additional Authors »

**Additional Authors**

G. Ghiringhelli, Y. Y. Peng, M. Hashimoto, B. Moritz, K. Kummer, N. B. Brookes, Y. He, S. Chen, S. Ishida, Y. Yoshida, H. Eisaki, M. Salluzzo, L. Braicovich, Z.-X. Shen, T. P. Devereaux & W.-S. Lee

**Abstract**

Experimental evidence on high-*T*c cuprates reveals ubiquitous charge density wave (CDW) modulations^{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, which coexist with superconductivity. Although the CDW had been predicted by theory^{11, 12, 13}, important questions remain about the extent to which the CDW influences lattice and charge degrees of freedom and its characteristics as functions of doping and temperature. These questions are intimately connected to the origin of the CDW and its relation to the mysterious cuprate pseudogap^{10, 14}. Here, we use ultrahigh-resolution resonant inelastic X-ray scattering to reveal new CDW character in underdoped Bi2.2Sr1.8Ca0.8Dy0.2Cu2O8+*δ*. At low temperature, we observe dispersive excitations from an incommensurate CDW that induces anomalously enhanced phonon intensity, unseen using other techniques. Near the pseudogap temperature *T*^{∗}, the CDW persists, but the associated excitations significantly weaken with an indication of CDW wavevector shift. The dispersive CDW excitations, phonon anomaly, and analysis of the CDW wavevector provide a comprehensive momentum-space picture of complex CDW behaviour and point to a closer relationship with the pseudogap state.

**"Ideal charge-density-wave order in the high-field state of superconducting YBCO"** — H. Jang: W.-S. Lee, H. Nojiri, S. Matsuzawa, H. Yasumura, L. Nie, A. V. Maharaj, S. Gerber, Y.-J. Liu, A. Mehta, D. A. Bonn, R. Liang, W. N. Hardy, C. A. Burns, Z. Islam, S. Song, J. Hastings, T. P. Devereaux, Z.-X. Shen, S. A. Kivelson, C.-C. Kao, D. Zhu, and J.-S. Lee; Proceedings of the National Academy of Sciences, 12/20/16.

Show Abstract » | Show Additional Authors »

**Additional Authors**

W.-S. Lee, H. Nojiri, S. Matsuzawa, H. Yasumura, L. Nie, A. V. Maharaj, S. Gerber, Y.-J. Liu, A. Mehta, D. A. Bonn, R. Liang, W. N. Hardy, C. A. Burns, Z. Islam, S. Song, J. Hastings, T. P. Devereaux, Z.-X. Shen, S. A. Kivelson, C.-C. Kao, D. Zhu, and J.-S. Lee

**Abstract**

The existence of charge-density-wave (CDW) correlations in cuprate superconductors has now been established. However, the nature of the CDW ground state has remained uncertain because disorder and the presence of superconductivity typically limit the CDW correlation lengths to only a dozen unit cells or less. Here we explore the field-induced 3D CDW correlations in extremely pure detwinned crystals of YBa_{2}Cu_{3}O_{2} (YBCO) ortho-II and ortho-VIII at magnetic fields in excess of the resistive upper critical field (Hc2Hc2) where superconductivity is heavily suppressed. We observe that the 3D CDW is unidirectional and possesses a long in-plane correlation length as well as significant correlations between neighboring CuO_{2}planes. It is significant that we observe only a single sharply defined transition at a critical field proportional to Hc2Hc2, given that the field range used in this investigation overlaps with other high-field experiments including quantum oscillation measurements. The correlation volume is at least two to three orders of magnitude larger than that of the zero-field CDW. This is by far the largest CDW correlation volume observed in any cuprate crystal and so is presumably representative of the high-field ground state of an “ideal” disorder-free cuprate.

**"Ising Nematic Quantum Critical Point in a Metal: A Monte Carlo Study"** — Yoni Schattner: Samuel Lederer, Steven A. Kivelson, and Erez Berg; American Physical Society, 08/23/16.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Samuel Lederer, Steven A. Kivelson, and Erez Berg

**Abstract**

The Ising nematic quantum critical point associated with the zero-temperature transition from a symmetric to a nematic metal is an exemplar of metallic quantum criticality. We carry out a minus-sign-free quantum Monte Carlo study of this quantum critical point for a two-dimensional lattice model with sizes up to 24×24 sites. For the parameters in this study, some (but not all) correlation functions exhibit scaling behavior over the accessible ranges of temperature, (imaginary) time, and distance, and the system remains nonsuperconducting down to the lowest accessible temperatures. The observed scaling behavior has remarkable similarities to recently measured properties of the Fe-based superconductors proximate to their putative nematic quantum critical point.

**"Cold-spots and glassy nematicity in underdoped cuprates"** — Kyungmin Lee: Steven A. Kivelson, and Eun-Ah Kim; Physical Review B, 07/11/16.

Show Abstract » | Show Additional Authors »

**Additional Authors**

Steven A. Kivelson, and Eun-Ah Kim

**Abstract**

There is now copious direct experimental evidence of various forms of (short-range) charge order in underdoped cuprate high temperature superconductors, and spectroscopic signatures of a nodal-antinodal dichotomy in the structure of the single-particle spectral functions. In this context we analyze the Bogoliubov quasiparticle spectrum in a superconducting nematic glass. The coincidence of the superconducting “nodal points” and the nematic “cold-spots” on the Fermi surface naturally accounts for many of the most salient features of the measured spectral functions (from angle-resolved photoemission) and the local density of states (from scanning tunneling microscopy).