Michael J Lawler | Binghamton University (original) (raw)

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Papers by Michael J Lawler

Research paper thumbnail of PNAS Plus Significance Statements

Research paper thumbnail of Phase Determination for Intra-unit-cell Fourier Transform STM--Picometer Registration of Zn Impurity States in Bi $ _ {2} $ Sr $ _ {2} $ CaCu $ _ {2} $ O $ _ {8+\ delta} $

Research paper thumbnail of Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates--Part I

Research paper thumbnail of Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates--Part II

Research paper thumbnail of Spectroscopic imaging STM studies of electronic structure in the superconducting and pseudogap phases of cuprate high-Tc superconductors

Research paper thumbnail of Intra-unit-cell nematic density wave: unified broken-symmetry of the cuprate pseudogap state

The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved... more The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved. However, evidence has been accumulating that this state may be an unconventional density wave. Here we carry out sitespecific measurements within each CuO2 unit-cell, segregating the results into three separate electronic structure images containing only the Cu sites (Cu(r)) and only the x/y-axis O sites (Ox(r) and Oy(r)). Phase resolved Fourier analysis reveals directly that the modulations in the Ox(r) and Oy(r) sublattice images consistently exhibit a relative phase of  We confirm this discovery on two highly distinct cuprate compounds, ruling out tunnel matrix-element and materials specific systematics. These observations demonstrate by direct sublattice phaseresolved visualization that the density wave found in underdoped cuprates consists of modulations of the intra-unit-cell states that exhibit a predominantly d-symmetry form factor.

Research paper thumbnail of Formation and consequences of heavy d-electron quasiparticles in Sr3Ru2O7

We report angle-resolved photoelectron spectroscopy measurements of the quantum critical metal Sr... more We report angle-resolved photoelectron spectroscopy measurements of the quantum critical metal Sr3Ru2O7 revealing itinerant Ru 4d-states confined over large parts of the Brillouin zone to an energy range of < ∼ 6 meV, nearly three orders of magnitude lower than the bare band width. We show that this energy scale agrees quantitatively with a characteristic thermodynamic energy scale associated with quantum criticality and illustrate how it arises from the hybridization of light and strongly renormalized, heavy quasiparticle bands. For the largest Fermi surface sheet we find a marked k-dependence of the renormalization and show that it correlates with the Ru 4d -O 2p hybridization. 71.27.+a, 71.18+y, The bilayer ruthenate Sr 3 Ru 2 O 7 exhibits intriguing thermodynamic and transport properties -including itinerant metamagnetism and electronic nematicity [1-7] -that are reminiscent of f -electron quantum critical heavy-fermion systems and have generated significant theoretical interest . These properties are remarkably different from the single layer strontium ruthenate Sr 2 RuO 4 and cannot be understood in an independent electron picture. Within band structure theory in the local density approximation (LDA), Sr 2 RuO 4 and Sr 3 Ru 2 O 7 have a wide bare conduction band, formed by relatively extended Ru 4d states hybridizing with O 2p electrons, and a similar density of states at the Fermi level. Despite the moderate Coulomb repulsion in the Ru 4d shell, a sizable correlation driven enhancement of the Sommerfeld coefficient of γ/γ LDA ≈ 4 is observed in Sr 2 RuO 4 which was recently argued to be a consequence of Hund's rule coupling reducing the coherence scale away from half filling . The even larger electronic specific heat of Sr 3 Ru 2 O 7 with γ/γ LDA ≈ 10 is indicative of enhanced electronic correlations in the bilayer system.

Research paper thumbnail of How Topological Defects Couple the Smectic and Nematic Electronic Structure of the Cuprate Pseudogap States

ABSTRACT We study the recently discovered coexisting smectic and nematic broken symmetries in the... more ABSTRACT We study the recently discovered coexisting smectic and nematic broken symmetries in the pseudogap-energy electronic structure of underdoped Bi2Sr2CaCu2O8+delta. By visualizing their spatial components separately, we discover 2pi topological defects throughout the phase-fluctuating smectic states. Imaging the locations of large numbers of these topological defects simultaneously with the fluctuations of the electronic nematicity about its average, reveals strong empirical evidence for a coupling between them. We also found the same phenomenology in a single layer compound of Bi2Sr1.6La0.4CuO6+delta. From these observations, we propose a Ginzburg-Landau free energy describing the quantum nematic/smectic coupling and demonstrate how it can explain the coexistence of these states and correctly predict their interplay at the atomic scale. This theoretical understanding of the coupling between the quantum nematic and smectic broken symmetries can lead to unraveling the complexities of the phase diagram of cuprate high-Tc superconductors[1]. [1]A. Mesaros, K. Fujita, H. Eisaki, S. Uchida, J. C. Davis, S. Sachdev, J. Zaanen, M. J. Lawler, and Eun-Ah Kim, Submitted (2010).

Research paper thumbnail of Understanding Quantum Phase Transitions

Condensed Matter Physics, 2010

... 922 KB). 241. Chapter 10. Topological Excitations in Superfluids with Internal Degrees of Fre... more ... 922 KB). 241. Chapter 10. Topological Excitations in Superfluids with Internal Degrees of Freedom Yuki Kawaguchi, Masahito Ueda Abstract - Hi-Res PDF (1920 KB) - PDF w/links (1079 KB). 265. Chapter 11. Quantum Monte ...

Research paper thumbnail of Effect of Dirac spinons on angle-resolved photoemission signatures of herbertsmithite

Physical Review B, 2013

ABSTRACT The spinon continues to be an elusive elementary excitation of frustrated antiferromagne... more ABSTRACT The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the angle resolved photoemission spectroscopy (ARPES) signatures of single-crystal samples of herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will be linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations of the mean-field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence of the existence of spinons in more than one dimensions.

Research paper thumbnail of Non-perturbative behavior of the Pomeranchuk quantum phase transition of a nematic Fermi fluid

... Fermi fluid. 12:15 PM–12:27 PM. Preview Abstract. Authors: Michael Lawler VictoriaFernandez E... more ... Fermi fluid. 12:15 PM–12:27 PM. Preview Abstract. Authors: Michael Lawler VictoriaFernandez Eduardo Fradkin (University of Illinois at Urbana-Champaign). A nematic phase of an electron gas was predicted by Oganesyan et. ...

Research paper thumbnail of Quantum electronic liquid crystals

Research paper thumbnail of Emergent paramagnetic phases in Zn-paratacamite (Topological Aspects of Solid State Physics)

Research paper thumbnail of Properties of a Single Hole in a Kagome Antiferromagnet

Research paper thumbnail of Highly frustrated magnets: a class of emergent gauge systems

Research paper thumbnail of Effect of Dirac Spinons on ARPES signatures of Herbertsmithe

The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To so... more The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the Angle Resolved Photoemission Spectroscopy (ARPES) signatures of single crystal samples of Herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will have a linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations to the mean field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence for the existence of spinons in greater than one dimension.

Research paper thumbnail of Emergent gauge dynamics of highly frustrated magnets

Condensed matter exhibit a wide variety of exotic emergent phenomena, such as the topological ord... more Condensed matter exhibit a wide variety of exotic emergent phenomena, such as the topological order in the fractional quantum Hall effect 1 , and the "cooperative paramagnetic" response of geometrically frustrated magnets 2 . Spins exploring the large configuration subspace associated with the latter 3,4 are dominated by collective behavior. Though spins in this emergent regime have been studied numerically 5-7 and analytically through an effective theory 7 , their classical and quantum dynamics are not well understood. I consider the constrained rials including Herbersmithite, the Jarosite family, SrCr 8−x G 4+x O 19 and Na 4 Ir 3 O 8 . Spins "suffering" this condition are highly frustrated for they have difficulty deciding between the continuously many arrangements that satisfy it. Such arrangements are described by the "spin origami" construction 14,15 of drawing spin vectors on a piece of paper and literally folding the paper to obtain new spin directions (see ). The resulting behavior of the spins is then collective and at finite temperatures, they enter a "cooperative" paramagnetic phase 2 . Furthermore, there is a wide class of other HFMs with similar constraints 16 such as the pyrochlore antiferromagnets where the analog of the spin origami construction leads to an effective Maxwell-like gauge description and dipolar spin correlations 5,7 . Because of their novel low energy properties due to their constrained mechanical behavior, HFMs continue to be promising materials 17 to search for new phases of matter.

Research paper thumbnail of Predictions for the ARPES spectral function of kagome antiferromagnetic insulators

There are now a number of spin liquid candidate materials possibly with exotic spin-1/2 "spi... more There are now a number of spin liquid candidate materials possibly with exotic spin-1/2 "spinon" excitations. Motivation by these discoveries, we consider the scaling properties of the hole spectral function for the frustrated Kagome Heisenberg antiferromagnet assuming Dirac Spin Liquid(DSL) ground state proposed for Herbertsmithite [2]. We predict a sublinear in energy power law dependence of the ARPES spectral function at certain wave vectors. Using Renormalization group techniques, we show how (gauge) fluctuations of the DSL mean field give an anomalous exponent to spinons[2] and no anomalous exponent to holons thereby leading to the sublinear power law. If this behavior is observed in experiments, they would provide strong evidence for the existence of spinons in highly frustrated magnets. ootnotetextY. Ran et al, Phys. Rev. Lett. 98, 117205 (2007)

Research paper thumbnail of Phase diagram of the anisotropic two-dimensional bilinear biquadratic spin-1 Heisenberg model

The anisotropic bilinear biquadratic Heisenberg model on a square lattice has been proposed to ex... more The anisotropic bilinear biquadratic Heisenberg model on a square lattice has been proposed to exhibit deconfined critical phenomena (DCP) based on QMC simulations and effective field theoretical studies [1, 2]. We investigate the phase transitions of the model using slave boson representation. Our mean field approach suggests a first order transition between the nematic and the disordered regime except at the tricritical SU(3) symmetric point. We will also discuss the relevance of our results to the DCP. [1] T. Grover and T. Senthil, Phys. Rev. Lett. 98, 247202 (2007) [2] K. Harada, N. Kawashima and M. Troyer, J. Phys. Soc. Jpn. 76, 013703 (2007)

Research paper thumbnail of Quantum Antiferromagnet on a Hyper-kagome Lattice: Applications to Na4Ir2O8

Motivated by the intriguing low temperature paramagnetic behaviour recently observed in the Mott ... more Motivated by the intriguing low temperature paramagnetic behaviour recently observed in the Mott insulator Na4Ir2O8, we study the quantum antiferromagnet Heisenberg model on a hyper-kagome lattice. Employing a large N generalization of the Schwinger boson description of spin systems uniquely suited to frustrated lattices, we find various closely competing phases for the ground state. Implications of our results for Na4Ir2O8 are also discussed.

Research paper thumbnail of PNAS Plus Significance Statements

Research paper thumbnail of Phase Determination for Intra-unit-cell Fourier Transform STM--Picometer Registration of Zn Impurity States in Bi $ _ {2} $ Sr $ _ {2} $ CaCu $ _ {2} $ O $ _ {8+\ delta} $

Research paper thumbnail of Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates--Part I

Research paper thumbnail of Intra unit cell electronic structure of the d-symmetry form factor density wave in the underdoped cuprates--Part II

Research paper thumbnail of Spectroscopic imaging STM studies of electronic structure in the superconducting and pseudogap phases of cuprate high-Tc superconductors

Research paper thumbnail of Intra-unit-cell nematic density wave: unified broken-symmetry of the cuprate pseudogap state

The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved... more The identity of the fundamental broken symmetry (if any) in the underdoped cuprates is unresolved. However, evidence has been accumulating that this state may be an unconventional density wave. Here we carry out sitespecific measurements within each CuO2 unit-cell, segregating the results into three separate electronic structure images containing only the Cu sites (Cu(r)) and only the x/y-axis O sites (Ox(r) and Oy(r)). Phase resolved Fourier analysis reveals directly that the modulations in the Ox(r) and Oy(r) sublattice images consistently exhibit a relative phase of  We confirm this discovery on two highly distinct cuprate compounds, ruling out tunnel matrix-element and materials specific systematics. These observations demonstrate by direct sublattice phaseresolved visualization that the density wave found in underdoped cuprates consists of modulations of the intra-unit-cell states that exhibit a predominantly d-symmetry form factor.

Research paper thumbnail of Formation and consequences of heavy d-electron quasiparticles in Sr3Ru2O7

We report angle-resolved photoelectron spectroscopy measurements of the quantum critical metal Sr... more We report angle-resolved photoelectron spectroscopy measurements of the quantum critical metal Sr3Ru2O7 revealing itinerant Ru 4d-states confined over large parts of the Brillouin zone to an energy range of < ∼ 6 meV, nearly three orders of magnitude lower than the bare band width. We show that this energy scale agrees quantitatively with a characteristic thermodynamic energy scale associated with quantum criticality and illustrate how it arises from the hybridization of light and strongly renormalized, heavy quasiparticle bands. For the largest Fermi surface sheet we find a marked k-dependence of the renormalization and show that it correlates with the Ru 4d -O 2p hybridization. 71.27.+a, 71.18+y, The bilayer ruthenate Sr 3 Ru 2 O 7 exhibits intriguing thermodynamic and transport properties -including itinerant metamagnetism and electronic nematicity [1-7] -that are reminiscent of f -electron quantum critical heavy-fermion systems and have generated significant theoretical interest . These properties are remarkably different from the single layer strontium ruthenate Sr 2 RuO 4 and cannot be understood in an independent electron picture. Within band structure theory in the local density approximation (LDA), Sr 2 RuO 4 and Sr 3 Ru 2 O 7 have a wide bare conduction band, formed by relatively extended Ru 4d states hybridizing with O 2p electrons, and a similar density of states at the Fermi level. Despite the moderate Coulomb repulsion in the Ru 4d shell, a sizable correlation driven enhancement of the Sommerfeld coefficient of γ/γ LDA ≈ 4 is observed in Sr 2 RuO 4 which was recently argued to be a consequence of Hund's rule coupling reducing the coherence scale away from half filling . The even larger electronic specific heat of Sr 3 Ru 2 O 7 with γ/γ LDA ≈ 10 is indicative of enhanced electronic correlations in the bilayer system.

Research paper thumbnail of How Topological Defects Couple the Smectic and Nematic Electronic Structure of the Cuprate Pseudogap States

ABSTRACT We study the recently discovered coexisting smectic and nematic broken symmetries in the... more ABSTRACT We study the recently discovered coexisting smectic and nematic broken symmetries in the pseudogap-energy electronic structure of underdoped Bi2Sr2CaCu2O8+delta. By visualizing their spatial components separately, we discover 2pi topological defects throughout the phase-fluctuating smectic states. Imaging the locations of large numbers of these topological defects simultaneously with the fluctuations of the electronic nematicity about its average, reveals strong empirical evidence for a coupling between them. We also found the same phenomenology in a single layer compound of Bi2Sr1.6La0.4CuO6+delta. From these observations, we propose a Ginzburg-Landau free energy describing the quantum nematic/smectic coupling and demonstrate how it can explain the coexistence of these states and correctly predict their interplay at the atomic scale. This theoretical understanding of the coupling between the quantum nematic and smectic broken symmetries can lead to unraveling the complexities of the phase diagram of cuprate high-Tc superconductors[1]. [1]A. Mesaros, K. Fujita, H. Eisaki, S. Uchida, J. C. Davis, S. Sachdev, J. Zaanen, M. J. Lawler, and Eun-Ah Kim, Submitted (2010).

Research paper thumbnail of Understanding Quantum Phase Transitions

Condensed Matter Physics, 2010

... 922 KB). 241. Chapter 10. Topological Excitations in Superfluids with Internal Degrees of Fre... more ... 922 KB). 241. Chapter 10. Topological Excitations in Superfluids with Internal Degrees of Freedom Yuki Kawaguchi, Masahito Ueda Abstract - Hi-Res PDF (1920 KB) - PDF w/links (1079 KB). 265. Chapter 11. Quantum Monte ...

Research paper thumbnail of Effect of Dirac spinons on angle-resolved photoemission signatures of herbertsmithite

Physical Review B, 2013

ABSTRACT The spinon continues to be an elusive elementary excitation of frustrated antiferromagne... more ABSTRACT The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the angle resolved photoemission spectroscopy (ARPES) signatures of single-crystal samples of herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will be linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations of the mean-field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence of the existence of spinons in more than one dimensions.

Research paper thumbnail of Non-perturbative behavior of the Pomeranchuk quantum phase transition of a nematic Fermi fluid

... Fermi fluid. 12:15 PM–12:27 PM. Preview Abstract. Authors: Michael Lawler VictoriaFernandez E... more ... Fermi fluid. 12:15 PM–12:27 PM. Preview Abstract. Authors: Michael Lawler VictoriaFernandez Eduardo Fradkin (University of Illinois at Urbana-Champaign). A nematic phase of an electron gas was predicted by Oganesyan et. ...

Research paper thumbnail of Quantum electronic liquid crystals

Research paper thumbnail of Emergent paramagnetic phases in Zn-paratacamite (Topological Aspects of Solid State Physics)

Research paper thumbnail of Properties of a Single Hole in a Kagome Antiferromagnet

Research paper thumbnail of Highly frustrated magnets: a class of emergent gauge systems

Research paper thumbnail of Effect of Dirac Spinons on ARPES signatures of Herbertsmithe

The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To so... more The spinon continues to be an elusive elementary excitation of frustrated antiferromagnets. To solidify evidence for its existence, we address the question of what will be the Angle Resolved Photoemission Spectroscopy (ARPES) signatures of single crystal samples of Herbertsmithite assuming it is described by the Dirac spin liquid state. In particular, we show that the electron spectral function will have a linear in energy dependence near specific wave vectors and that this dependence is expected even after fluctuations to the mean field values are taken into account. Observation of this unique signature in ARPES will provide very strong evidence for the existence of spinons in greater than one dimension.

Research paper thumbnail of Emergent gauge dynamics of highly frustrated magnets

Condensed matter exhibit a wide variety of exotic emergent phenomena, such as the topological ord... more Condensed matter exhibit a wide variety of exotic emergent phenomena, such as the topological order in the fractional quantum Hall effect 1 , and the "cooperative paramagnetic" response of geometrically frustrated magnets 2 . Spins exploring the large configuration subspace associated with the latter 3,4 are dominated by collective behavior. Though spins in this emergent regime have been studied numerically 5-7 and analytically through an effective theory 7 , their classical and quantum dynamics are not well understood. I consider the constrained rials including Herbersmithite, the Jarosite family, SrCr 8−x G 4+x O 19 and Na 4 Ir 3 O 8 . Spins "suffering" this condition are highly frustrated for they have difficulty deciding between the continuously many arrangements that satisfy it. Such arrangements are described by the "spin origami" construction 14,15 of drawing spin vectors on a piece of paper and literally folding the paper to obtain new spin directions (see ). The resulting behavior of the spins is then collective and at finite temperatures, they enter a "cooperative" paramagnetic phase 2 . Furthermore, there is a wide class of other HFMs with similar constraints 16 such as the pyrochlore antiferromagnets where the analog of the spin origami construction leads to an effective Maxwell-like gauge description and dipolar spin correlations 5,7 . Because of their novel low energy properties due to their constrained mechanical behavior, HFMs continue to be promising materials 17 to search for new phases of matter.

Research paper thumbnail of Predictions for the ARPES spectral function of kagome antiferromagnetic insulators

There are now a number of spin liquid candidate materials possibly with exotic spin-1/2 "spi... more There are now a number of spin liquid candidate materials possibly with exotic spin-1/2 "spinon" excitations. Motivation by these discoveries, we consider the scaling properties of the hole spectral function for the frustrated Kagome Heisenberg antiferromagnet assuming Dirac Spin Liquid(DSL) ground state proposed for Herbertsmithite [2]. We predict a sublinear in energy power law dependence of the ARPES spectral function at certain wave vectors. Using Renormalization group techniques, we show how (gauge) fluctuations of the DSL mean field give an anomalous exponent to spinons[2] and no anomalous exponent to holons thereby leading to the sublinear power law. If this behavior is observed in experiments, they would provide strong evidence for the existence of spinons in highly frustrated magnets. ootnotetextY. Ran et al, Phys. Rev. Lett. 98, 117205 (2007)

Research paper thumbnail of Phase diagram of the anisotropic two-dimensional bilinear biquadratic spin-1 Heisenberg model

The anisotropic bilinear biquadratic Heisenberg model on a square lattice has been proposed to ex... more The anisotropic bilinear biquadratic Heisenberg model on a square lattice has been proposed to exhibit deconfined critical phenomena (DCP) based on QMC simulations and effective field theoretical studies [1, 2]. We investigate the phase transitions of the model using slave boson representation. Our mean field approach suggests a first order transition between the nematic and the disordered regime except at the tricritical SU(3) symmetric point. We will also discuss the relevance of our results to the DCP. [1] T. Grover and T. Senthil, Phys. Rev. Lett. 98, 247202 (2007) [2] K. Harada, N. Kawashima and M. Troyer, J. Phys. Soc. Jpn. 76, 013703 (2007)

Research paper thumbnail of Quantum Antiferromagnet on a Hyper-kagome Lattice: Applications to Na4Ir2O8

Motivated by the intriguing low temperature paramagnetic behaviour recently observed in the Mott ... more Motivated by the intriguing low temperature paramagnetic behaviour recently observed in the Mott insulator Na4Ir2O8, we study the quantum antiferromagnet Heisenberg model on a hyper-kagome lattice. Employing a large N generalization of the Schwinger boson description of spin systems uniquely suited to frustrated lattices, we find various closely competing phases for the ground state. Implications of our results for Na4Ir2O8 are also discussed.