Kamalesh Chatterjee - Academia.edu (original) (raw)

Papers by Kamalesh Chatterjee

Research paper thumbnail of Unity power factor single phase AC line current conditioner

Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129), 2000

Electronic equipment used for data processing typically feature a simple diode bridge rectifier a... more Electronic equipment used for data processing typically feature a simple diode bridge rectifier at the front end of the power circuit. The rectifier, in conjunction with its capacitive filter is a nonlinear load and draws current with high crest factor and is rich in harmonics, which cause power quality problems. Such problems have prompted the development of unity power factor rectifiers, which use active current shaping techniques. However, such unity power factor rectifiers have not found widespread application in commercial data processing equipment, mainly due to the absence of persistent problems related to power quality and higher premium being placed on processor speed, memory size, etc. This paper presents an alternative approach to solve power quality problems in such scenarios, only when the problem becomes severe and causes persistent malfunction. A unity power factor line current conditioner based on a boost type AC to AC converter topology is proposed. The paper presents a detailed analysis of the evolution of the converter topology, operation, and design. Experimental results for a prototype converter are included

Research paper thumbnail of Suppression of Superfluid Density and the Pseudogap State in the Cuprates by Impurities

Physical review letters, Jan 16, 2016

We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped in... more We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped into the high-temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}. Our spectroscopic measurements reveal that Fe impurities introduce low-lying resonances in the density of states at Ω_{1}≈4 meV and Ω_{2}≈15 meV, allowing us to determine that, despite having a large magnetic moment, potential scattering of quasiparticles by Fe impurities dominates magnetic scattering. In addition, using high-resolution spatial characterizations of the local density of states near and away from Fe impurities, we detail the spatial extent of impurity-affected regions as well as provide a local view of impurity-induced effects on the superconducting and pseudogap states. Our studies of Fe impurities, when combined with a reinterpretation of earlier STM work in the context of a two-gap scenario, allow us to present a unified view of the atomic-scale effects of elemental impurities on the pseudogap and sup...

Research paper thumbnail of Temperature dependent Scanning Tunneling Spectroscopy of impurities in Bi2Sr2CuO6+x through the transition temperature

Scanning Tunneling Microscopy has been used to study detailed electronic spectrum in atomic scale... more Scanning Tunneling Microscopy has been used to study detailed electronic spectrum in atomic scale defects in high temperature superconductors. We present Scanning Tunneling Spectroscopy of impurities in Bi2Sr2CuO6+x (Bi-2201) over a wide range of temperatures. Surprisingly, native impurity resonances, similar to the ones previously observed in Bi2Sr2CaCu2O8+x (Bi-2212), spatially coexist with the superconducting gap at low temperatures and survive almost unchanged through the superconducting transition temperature Tc. We shall discuss the implications of these findings on the relationship between superconducting gap and pseudogap in these materials.

Research paper thumbnail of High Temperature 300C Directional Drilling System

Research paper thumbnail of Fermi surface pairing & coherence in a high Tc superconductor

ABSTRACT Superconductivity arises from the pairing of electrons on the Fermi surface. In high tem... more ABSTRACT Superconductivity arises from the pairing of electrons on the Fermi surface. In high temperature cuprate superconductors, evidence compiled from several materials suggests that the Fermi surface expands at a critical doping. However, the nature of the altered Fermi surface, its availability for pairing, and its relationship to the long-mysterious pseudogap phase are unknown. Here we use scanning tunneling microscopy to reveal a quantum phase transition in Fermi surface topology within a single material (PbxBi2-x)LaySr2-yCuO6+z (Bi2201). In lightly doped samples, the Fermi surface terminates at the antiferromagnetic Brillouin zone boundary, but upon increased doping we detect a new Fermi surface component extending to the antinode. We use phase-sensitive quasiparticle interference mapping to prove that d-wave Bogoliubov quasiparticles exist on this recovered antinodal Fermi surface despite the coexisting pseudogap. By magnetic-field-dependent imaging, we finally identify the competitive role of the pseudogap: it inhomogeneously suppresses superconducting phase coherence, while leaving a robust superconducting gap intact. The discovery of these three phenomena within a single cuprate material provides a new basis for understanding the phenomenology of high-Tc superconductivity.

Research paper thumbnail of Fermi Surface and Pseudogap Evolution in a Cuprate Superconductor

Science, 2014

The unclear relationship between cuprate superconductivity and the pseudogap state remains an imp... more The unclear relationship between cuprate superconductivity and the pseudogap state remains an impediment to understanding the high transition temperature (T(c)) superconducting mechanism. Here, we used magnetic field-dependent scanning tunneling microscopy to provide phase-sensitive proof that d-wave superconductivity coexists with the pseudogap on the antinodal Fermi surface of an overdoped cuprate. Furthermore, by tracking the hole-doping (p) dependence of the quasi-particle interference pattern within a single bismuth-based cuprate family, we observed a Fermi surface reconstruction slightly below optimal doping, indicating a zero-field quantum phase transition in notable proximity to the maximum superconducting T(c). Surprisingly, this major reorganization of the system's underlying electronic structure has no effect on the smoothly evolving pseudogap.

Research paper thumbnail of An auxiliary capacitor based ultrafast drive circuit for shear piezoelectric motors

Review of Scientific Instruments, 2009

Chatterjee, Kamalesh et al. "An auxiliary capacitor based ultrafast drive circuit for shear piezo... more Chatterjee, Kamalesh et al. "An auxiliary capacitor based ultrafast drive circuit for shear piezoelectric motors." Review of Scientific Instruments 80.9 (2009): 095110-5.

Research paper thumbnail of Charge-density-wave origin of cuprate checkerboard visualized by scanning tunnelling microscopy

Nature Physics, 2008

One of the main challenges in understanding high-T c superconductivity is to disentangle the rich... more One of the main challenges in understanding high-T c superconductivity is to disentangle the rich variety of states of matter that may coexist, cooperate or compete with d-wave superconductivity. At centre stage is the pseudogap phase, which occupies a large ...

Research paper thumbnail of Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Nature Physics, 2009

Comment on "Visualization of the interplay between high-temperature superconductivity, the pseudo... more Comment on "Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances" (K. Chatterjee et al., Nature Phys. 4, 108 In a recent letter, Chatterjee et al. reported tunnelling data obtained below and above the critical temperature (T c = 15 K) by STM in overdoped Bi 2-y Pb y Sr 2 CuO 6+x (Bi2201) and some interpretations of

Research paper thumbnail of Imaging nanoscale Fermi-surface variations in an inhomogeneous superconductor

Nature Physics, 2009

Particle-wave duality suggests we think of electrons as waves stretched across a sample, with wav... more Particle-wave duality suggests we think of electrons as waves stretched across a sample, with wavevector k proportional to their momentum. Their arrangement in "k-space," and in particular the shape of the Fermi surface, where the highest energy electrons of the system reside, determine many material properties. Here we use a novel extension of Fourier transform scanning tunneling microscopy to probe the Fermi surface of the strongly inhomogeneous Bi-based cuprate superconductors. Surprisingly, we find that rather than being globally defined, the Fermi surface changes on nanometer length scales. Just as shifting tide lines expose variations of water height, changing Fermi surfaces indicate strong local doping variations. This discovery, unprecedented in any material, paves the way for an understanding of other inhomogeneous characteristics of the cuprates, like the pseudogap magnitude, and highlights a new approach to the study of nanoscale inhomogeneity in general.

Research paper thumbnail of Scanning tunnelling microscopy imaging of symmetry-breaking structural distortion in the bismuth-based cuprate superconductors

Nature Materials, 2012

A complicating factor in unraveling the theory of high-temperature (high-T c ) superconductivity ... more A complicating factor in unraveling the theory of high-temperature (high-T c ) superconductivity is the presence of a "pseudogap" in the density of states, whose origin has been debated since its discovery 1 . Some believe the pseudogap is a broken symmetry state distinct from superconductivity 2-4 , while others believe it arises from short-range correlations without symmetry breaking 5,6 . A number of broken symmetries have been imaged and identified with the pseudogap state 7,8 , but it remains crucial to disentangle any electronic symmetry breaking from pre-existing structural symmetry of the crystal. We use scanning tunneling microscopy (STM) to observe an orthorhombic structural distortion across the cuprate superconducting Bi 2 Sr 2 Ca n-1 Cu n O 2n+4+x (BSCCO) family tree, which breaks twodimensional inversion symmetry in the surface BiO layer. Although this inversion symmetry breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field, and doping, that it cannot be the long-sought pseudogap state.

Research paper thumbnail of Visualizing antinodal pair decoherence in a high T $ _ {\ mathrm {c}} $ cuprate

ABSTRACT The relationship between the pseudogap phase and superconductivity in the cuprate superc... more ABSTRACT The relationship between the pseudogap phase and superconductivity in the cuprate superconductors remains mysterious. We use Fourier transform scanning tunneling spectroscopy to study the pseudogap in the cuprate superconductor Bi2-xPbxSr2CuO6+δ. We discover a new type of quasiparticle interference in the antinodal regions, presumed to be dominated by the pseudogap. Magnetic field induced spectral weight transfer shows that the pseudogap suppresses superconducting coherence but does not affect d-wave pairing at the antinode.

Research paper thumbnail of Atomic Scale Investigation of the Effects of Pb doping in Bi $ _ {2} $ Sr $ _ {2} $ CuO $ _ {6+ x} $

In the study of the Bi-based high temperature superconducting cuprates, an incommensurate structu... more In the study of the Bi-based high temperature superconducting cuprates, an incommensurate structural ``supermodulation'' that runs throughout the crystal can often lead to experimental complications, especially for scattering studies. In order to eliminate this problem, a ...

Research paper thumbnail of Scanning Tunneling Spectroscopy of Bi $ _ {2} $ Sr $ _ {2} $ CuO $ _ {6+ x} $

Scanning tunneling microscopy has revealed many interesting spectral features of the high tempera... more Scanning tunneling microscopy has revealed many interesting spectral features of the high temperature superconductors, including the nature of atomic scale defects like single atom impurities and magnetic vortices and the existence of inhomogeneity. Most of these studies have ...

Research paper thumbnail of New insights into cuprate superconductivity and pseudogap by STM of BSCCO

... Gregory Lau (MIT). MC Boyer (MIT). WD Wise (MIT). Kamalesh Chatterjee (Baker Hughes).Michelle... more ... Gregory Lau (MIT). MC Boyer (MIT). WD Wise (MIT). Kamalesh Chatterjee (Baker Hughes).Michelle Tomasik (MIT). Laura Popa (MIT). Takeshi Kondo (Ames Laboratory and Dept. of Physics and Astronomy, Iowa State University). Tsunehiro Takeuchi (Nagoya University). ...

Research paper thumbnail of STM imaging of inversion-symmetry-breaking structural distortion in the Bi-based cuprate superconductors

We use scanning tunneling microscopy to image an orthorhombic structural distortion across the cu... more We use scanning tunneling microscopy to image an orthorhombic structural distortion across the cuprate superconducting Bi 2 Sr 2 Ca n-1 Cu n O 2n+4+x family tree. We find the surface BiO plane to consist of two Bi sublattices, shifted by about one percent of the unit cell along the orthorhombic a-axis, breaking inversion symmetry at the Cu site, but preserving a mirror plane along this a-axis. We track the structure as a function of doping, temperature and magnetic field, but find no dependence of the magnitude of the shift on these parameters. Most importantly, we image twin boundaries in this structural distortion, providing a clear local picture of the preserved and broken mirror symmetries of the structural unit cell.

Research paper thumbnail of Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+ x

The nature of the pseudogap state, observed above the superconducting transition temperature T C ... more The nature of the pseudogap state, observed above the superconducting transition temperature T C in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi 2 Sr 2 CuO 6+x . We have found a new, narrow, homogeneous gap that vanishes near T C , superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.

Research paper thumbnail of Scanning tunneling microscopy of the 32 K

Arxiv preprint arXiv: …, 2008

Scanning tunneling microscopy of the 32 K superconductor ... MC Boyer1, Kamalesh Chatterjee1, WD ... more Scanning tunneling microscopy of the 32 K superconductor ... MC Boyer1, Kamalesh Chatterjee1, WD Wise1, GF Chen2, JL Luo2, NL Wang2, EW Hudson1 ... 1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2 Beijing ...

Research paper thumbnail of High-Resolution Scanning Tunneling Microscopy Characterization of Mixed Monolayer Protected Gold Nanoparticles

Research paper thumbnail of Imaging the two gaps of the high-temperature superconductor Bi 2 Sr 2 CuO 6+x

The nature and behaviour of electronic states in high-temperature superconductors are the centre ... more The nature and behaviour of electronic states in high-temperature superconductors are the centre of much debate. The pseudogap state, observed above the superconducting transition temperature, T c , is seen by some as a precursor to the superconducting state. Others view it as a competing phase. Recently, this discussion has focused on the number of energy gaps in the system. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here, we use temperature-dependent scanning tunnelling spectroscopy of (Bi 1−y Pb y) 2 Sr 2 CuO 6+x to clarify the situation. We find a previously unobserved narrow and homogeneous gap that vanishes near T c , superimposed on the typically observed inhomogeneous and broad gap, which is only weakly temperature dependent. These results not only support the two-gap picture, but also explain previously troubling differences between scanning tunnelling microscopy and other experimental measurements.

Research paper thumbnail of Unity power factor single phase AC line current conditioner

Conference Record of the 2000 IEEE Industry Applications Conference. Thirty-Fifth IAS Annual Meeting and World Conference on Industrial Applications of Electrical Energy (Cat. No.00CH37129), 2000

Electronic equipment used for data processing typically feature a simple diode bridge rectifier a... more Electronic equipment used for data processing typically feature a simple diode bridge rectifier at the front end of the power circuit. The rectifier, in conjunction with its capacitive filter is a nonlinear load and draws current with high crest factor and is rich in harmonics, which cause power quality problems. Such problems have prompted the development of unity power factor rectifiers, which use active current shaping techniques. However, such unity power factor rectifiers have not found widespread application in commercial data processing equipment, mainly due to the absence of persistent problems related to power quality and higher premium being placed on processor speed, memory size, etc. This paper presents an alternative approach to solve power quality problems in such scenarios, only when the problem becomes severe and causes persistent malfunction. A unity power factor line current conditioner based on a boost type AC to AC converter topology is proposed. The paper presents a detailed analysis of the evolution of the converter topology, operation, and design. Experimental results for a prototype converter are included

Research paper thumbnail of Suppression of Superfluid Density and the Pseudogap State in the Cuprates by Impurities

Physical review letters, Jan 16, 2016

We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped in... more We use scanning tunneling microscopy (STM) to study magnetic Fe impurities intentionally doped into the high-temperature superconductor Bi_{2}Sr_{2}CaCu_{2}O_{8+δ}. Our spectroscopic measurements reveal that Fe impurities introduce low-lying resonances in the density of states at Ω_{1}≈4 meV and Ω_{2}≈15 meV, allowing us to determine that, despite having a large magnetic moment, potential scattering of quasiparticles by Fe impurities dominates magnetic scattering. In addition, using high-resolution spatial characterizations of the local density of states near and away from Fe impurities, we detail the spatial extent of impurity-affected regions as well as provide a local view of impurity-induced effects on the superconducting and pseudogap states. Our studies of Fe impurities, when combined with a reinterpretation of earlier STM work in the context of a two-gap scenario, allow us to present a unified view of the atomic-scale effects of elemental impurities on the pseudogap and sup...

Research paper thumbnail of Temperature dependent Scanning Tunneling Spectroscopy of impurities in Bi2Sr2CuO6+x through the transition temperature

Scanning Tunneling Microscopy has been used to study detailed electronic spectrum in atomic scale... more Scanning Tunneling Microscopy has been used to study detailed electronic spectrum in atomic scale defects in high temperature superconductors. We present Scanning Tunneling Spectroscopy of impurities in Bi2Sr2CuO6+x (Bi-2201) over a wide range of temperatures. Surprisingly, native impurity resonances, similar to the ones previously observed in Bi2Sr2CaCu2O8+x (Bi-2212), spatially coexist with the superconducting gap at low temperatures and survive almost unchanged through the superconducting transition temperature Tc. We shall discuss the implications of these findings on the relationship between superconducting gap and pseudogap in these materials.

Research paper thumbnail of High Temperature 300C Directional Drilling System

Research paper thumbnail of Fermi surface pairing & coherence in a high Tc superconductor

ABSTRACT Superconductivity arises from the pairing of electrons on the Fermi surface. In high tem... more ABSTRACT Superconductivity arises from the pairing of electrons on the Fermi surface. In high temperature cuprate superconductors, evidence compiled from several materials suggests that the Fermi surface expands at a critical doping. However, the nature of the altered Fermi surface, its availability for pairing, and its relationship to the long-mysterious pseudogap phase are unknown. Here we use scanning tunneling microscopy to reveal a quantum phase transition in Fermi surface topology within a single material (PbxBi2-x)LaySr2-yCuO6+z (Bi2201). In lightly doped samples, the Fermi surface terminates at the antiferromagnetic Brillouin zone boundary, but upon increased doping we detect a new Fermi surface component extending to the antinode. We use phase-sensitive quasiparticle interference mapping to prove that d-wave Bogoliubov quasiparticles exist on this recovered antinodal Fermi surface despite the coexisting pseudogap. By magnetic-field-dependent imaging, we finally identify the competitive role of the pseudogap: it inhomogeneously suppresses superconducting phase coherence, while leaving a robust superconducting gap intact. The discovery of these three phenomena within a single cuprate material provides a new basis for understanding the phenomenology of high-Tc superconductivity.

Research paper thumbnail of Fermi Surface and Pseudogap Evolution in a Cuprate Superconductor

Science, 2014

The unclear relationship between cuprate superconductivity and the pseudogap state remains an imp... more The unclear relationship between cuprate superconductivity and the pseudogap state remains an impediment to understanding the high transition temperature (T(c)) superconducting mechanism. Here, we used magnetic field-dependent scanning tunneling microscopy to provide phase-sensitive proof that d-wave superconductivity coexists with the pseudogap on the antinodal Fermi surface of an overdoped cuprate. Furthermore, by tracking the hole-doping (p) dependence of the quasi-particle interference pattern within a single bismuth-based cuprate family, we observed a Fermi surface reconstruction slightly below optimal doping, indicating a zero-field quantum phase transition in notable proximity to the maximum superconducting T(c). Surprisingly, this major reorganization of the system's underlying electronic structure has no effect on the smoothly evolving pseudogap.

Research paper thumbnail of An auxiliary capacitor based ultrafast drive circuit for shear piezoelectric motors

Review of Scientific Instruments, 2009

Chatterjee, Kamalesh et al. "An auxiliary capacitor based ultrafast drive circuit for shear piezo... more Chatterjee, Kamalesh et al. "An auxiliary capacitor based ultrafast drive circuit for shear piezoelectric motors." Review of Scientific Instruments 80.9 (2009): 095110-5.

Research paper thumbnail of Charge-density-wave origin of cuprate checkerboard visualized by scanning tunnelling microscopy

Nature Physics, 2008

One of the main challenges in understanding high-T c superconductivity is to disentangle the rich... more One of the main challenges in understanding high-T c superconductivity is to disentangle the rich variety of states of matter that may coexist, cooperate or compete with d-wave superconductivity. At centre stage is the pseudogap phase, which occupies a large ...

Research paper thumbnail of Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances

Nature Physics, 2009

Comment on "Visualization of the interplay between high-temperature superconductivity, the pseudo... more Comment on "Visualization of the interplay between high-temperature superconductivity, the pseudogap and impurity resonances" (K. Chatterjee et al., Nature Phys. 4, 108 In a recent letter, Chatterjee et al. reported tunnelling data obtained below and above the critical temperature (T c = 15 K) by STM in overdoped Bi 2-y Pb y Sr 2 CuO 6+x (Bi2201) and some interpretations of

Research paper thumbnail of Imaging nanoscale Fermi-surface variations in an inhomogeneous superconductor

Nature Physics, 2009

Particle-wave duality suggests we think of electrons as waves stretched across a sample, with wav... more Particle-wave duality suggests we think of electrons as waves stretched across a sample, with wavevector k proportional to their momentum. Their arrangement in "k-space," and in particular the shape of the Fermi surface, where the highest energy electrons of the system reside, determine many material properties. Here we use a novel extension of Fourier transform scanning tunneling microscopy to probe the Fermi surface of the strongly inhomogeneous Bi-based cuprate superconductors. Surprisingly, we find that rather than being globally defined, the Fermi surface changes on nanometer length scales. Just as shifting tide lines expose variations of water height, changing Fermi surfaces indicate strong local doping variations. This discovery, unprecedented in any material, paves the way for an understanding of other inhomogeneous characteristics of the cuprates, like the pseudogap magnitude, and highlights a new approach to the study of nanoscale inhomogeneity in general.

Research paper thumbnail of Scanning tunnelling microscopy imaging of symmetry-breaking structural distortion in the bismuth-based cuprate superconductors

Nature Materials, 2012

A complicating factor in unraveling the theory of high-temperature (high-T c ) superconductivity ... more A complicating factor in unraveling the theory of high-temperature (high-T c ) superconductivity is the presence of a "pseudogap" in the density of states, whose origin has been debated since its discovery 1 . Some believe the pseudogap is a broken symmetry state distinct from superconductivity 2-4 , while others believe it arises from short-range correlations without symmetry breaking 5,6 . A number of broken symmetries have been imaged and identified with the pseudogap state 7,8 , but it remains crucial to disentangle any electronic symmetry breaking from pre-existing structural symmetry of the crystal. We use scanning tunneling microscopy (STM) to observe an orthorhombic structural distortion across the cuprate superconducting Bi 2 Sr 2 Ca n-1 Cu n O 2n+4+x (BSCCO) family tree, which breaks twodimensional inversion symmetry in the surface BiO layer. Although this inversion symmetry breaking structure can impact electronic measurements, we show from its insensitivity to temperature, magnetic field, and doping, that it cannot be the long-sought pseudogap state.

Research paper thumbnail of Visualizing antinodal pair decoherence in a high T $ _ {\ mathrm {c}} $ cuprate

ABSTRACT The relationship between the pseudogap phase and superconductivity in the cuprate superc... more ABSTRACT The relationship between the pseudogap phase and superconductivity in the cuprate superconductors remains mysterious. We use Fourier transform scanning tunneling spectroscopy to study the pseudogap in the cuprate superconductor Bi2-xPbxSr2CuO6+δ. We discover a new type of quasiparticle interference in the antinodal regions, presumed to be dominated by the pseudogap. Magnetic field induced spectral weight transfer shows that the pseudogap suppresses superconducting coherence but does not affect d-wave pairing at the antinode.

Research paper thumbnail of Atomic Scale Investigation of the Effects of Pb doping in Bi $ _ {2} $ Sr $ _ {2} $ CuO $ _ {6+ x} $

In the study of the Bi-based high temperature superconducting cuprates, an incommensurate structu... more In the study of the Bi-based high temperature superconducting cuprates, an incommensurate structural ``supermodulation'' that runs throughout the crystal can often lead to experimental complications, especially for scattering studies. In order to eliminate this problem, a ...

Research paper thumbnail of Scanning Tunneling Spectroscopy of Bi $ _ {2} $ Sr $ _ {2} $ CuO $ _ {6+ x} $

Scanning tunneling microscopy has revealed many interesting spectral features of the high tempera... more Scanning tunneling microscopy has revealed many interesting spectral features of the high temperature superconductors, including the nature of atomic scale defects like single atom impurities and magnetic vortices and the existence of inhomogeneity. Most of these studies have ...

Research paper thumbnail of New insights into cuprate superconductivity and pseudogap by STM of BSCCO

... Gregory Lau (MIT). MC Boyer (MIT). WD Wise (MIT). Kamalesh Chatterjee (Baker Hughes).Michelle... more ... Gregory Lau (MIT). MC Boyer (MIT). WD Wise (MIT). Kamalesh Chatterjee (Baker Hughes).Michelle Tomasik (MIT). Laura Popa (MIT). Takeshi Kondo (Ames Laboratory and Dept. of Physics and Astronomy, Iowa State University). Tsunehiro Takeuchi (Nagoya University). ...

Research paper thumbnail of STM imaging of inversion-symmetry-breaking structural distortion in the Bi-based cuprate superconductors

We use scanning tunneling microscopy to image an orthorhombic structural distortion across the cu... more We use scanning tunneling microscopy to image an orthorhombic structural distortion across the cuprate superconducting Bi 2 Sr 2 Ca n-1 Cu n O 2n+4+x family tree. We find the surface BiO plane to consist of two Bi sublattices, shifted by about one percent of the unit cell along the orthorhombic a-axis, breaking inversion symmetry at the Cu site, but preserving a mirror plane along this a-axis. We track the structure as a function of doping, temperature and magnetic field, but find no dependence of the magnitude of the shift on these parameters. Most importantly, we image twin boundaries in this structural distortion, providing a clear local picture of the preserved and broken mirror symmetries of the structural unit cell.

Research paper thumbnail of Imaging the Two Gaps of the High-TC Superconductor Pb-Bi2Sr2CuO6+ x

The nature of the pseudogap state, observed above the superconducting transition temperature T C ... more The nature of the pseudogap state, observed above the superconducting transition temperature T C in many high temperature superconductors, is the center of much debate. Recently, this discussion has focused on the number of energy gaps in these materials. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here we report on temperature dependent scanning tunneling spectroscopy of Pb-Bi 2 Sr 2 CuO 6+x . We have found a new, narrow, homogeneous gap that vanishes near T C , superimposed on the typically observed, inhomogeneous, broad gap, which is only weakly temperature dependent. These results not only support the two gap picture, but also explain previously troubling differences between scanning tunneling microscopy and other experimental measurements.

Research paper thumbnail of Scanning tunneling microscopy of the 32 K

Arxiv preprint arXiv: …, 2008

Scanning tunneling microscopy of the 32 K superconductor ... MC Boyer1, Kamalesh Chatterjee1, WD ... more Scanning tunneling microscopy of the 32 K superconductor ... MC Boyer1, Kamalesh Chatterjee1, WD Wise1, GF Chen2, JL Luo2, NL Wang2, EW Hudson1 ... 1 Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2 Beijing ...

Research paper thumbnail of High-Resolution Scanning Tunneling Microscopy Characterization of Mixed Monolayer Protected Gold Nanoparticles

Research paper thumbnail of Imaging the two gaps of the high-temperature superconductor Bi 2 Sr 2 CuO 6+x

The nature and behaviour of electronic states in high-temperature superconductors are the centre ... more The nature and behaviour of electronic states in high-temperature superconductors are the centre of much debate. The pseudogap state, observed above the superconducting transition temperature, T c , is seen by some as a precursor to the superconducting state. Others view it as a competing phase. Recently, this discussion has focused on the number of energy gaps in the system. Some experiments indicate a single energy gap, implying that the pseudogap is a precursor state. Others indicate two, suggesting that it is a competing or coexisting phase. Here, we use temperature-dependent scanning tunnelling spectroscopy of (Bi 1−y Pb y) 2 Sr 2 CuO 6+x to clarify the situation. We find a previously unobserved narrow and homogeneous gap that vanishes near T c , superimposed on the typically observed inhomogeneous and broad gap, which is only weakly temperature dependent. These results not only support the two-gap picture, but also explain previously troubling differences between scanning tunnelling microscopy and other experimental measurements.