Condensed Matter

Displaying 985 - 996 of 1172

Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Zhihao Hao University of Waterloo
April 25, 2013

PIRSA:13040134
Condensed Matter
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

Radu Coldea University of Oxford
April 25, 2013

PIRSA:13040133
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 14
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 25, 2013

PIRSA:13040060
Condensed Matter
Electronic Liquid Crystalline Phases of Highly Correlated Electronic Systems
April 24, 2013

PIRSA:13040116
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 13
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 24, 2013

PIRSA:13040059
Condensed Matter
Quantum transport in one dimension: from integrability to many-body localization and topology

Joel Moore University of California, Berkeley
April 23, 2013

PIRSA:13040125
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 12
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 23, 2013

PIRSA:13040058
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 11
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 22, 2013

PIRSA:13040057
Condensed Matter
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics
April 10, 2013

PIRSA:13040117
Condensed Matter
S=1 spin liquid with fermionic excitations

Maksym Serbyn Massachusetts Institute of Technology (MIT)
March 28, 2013

PIRSA:13030113
Condensed Matter
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Michael Hermele University of Colorado Boulder
March 26, 2013

PIRSA:13030116
Condensed Matter

Absence of Pauling's Residual Entropy in Dy2Ti2O

Jan Kycia University of Waterloo
April 25, 2013

PIRSA:13040130
Condensed Matter
The discovery of the spin-ice phase in Dy2Ti2O7 numbers among the most significant findings in magnetic materials in over a decade. The spin-ice model is based on an elegant analogy to Pauling’s model of geometrical frustration in water ice, and predicts the same residual entropy, as confirmed by numerous measurements. Melko, den Hertog and Gingras, with numerical work using a loop algorithm to speed up equilibration times, were able to determine an ordering for this system. This had not been seen experimentally observed by several groups. I will present new experimental results for the specific heat of Dy2Ti2O7, demonstrating why previous measurements were unable to correctly capture its low temperature behaviour. By carefully tracking the flow of heat into and out of the material, we observe a non-vanishing specific heat at low temperatures indicating the residual entropy does not actually agree with the Pauling value.
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Zhihao Hao University of Waterloo
April 25, 2013

PIRSA:13040134
Condensed Matter
Motivated by recent numerical and experimental studies of the spin-1/2 Heisenberg antiferromagnet on kagome, we formulate a many-body model for fermionic spinons, which are just uncoupled spins. The spinons interact with an emergent U(1) gauge field and experience strong short-range attraction in the S=0 channel. The ground state of the model is generically a Z(2) liquid. We calculate the edge of the two-spinon continuum and compare the theory to the slave-fermion approach to the Heisenberg model.
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

Radu Coldea University of Oxford
April 25, 2013

PIRSA:13040133
Condensed Matter
Realizing experimentally continuous phase transitions in the electronic ground state of materials near zero temperature as a function of tuning some external parameter (magnetic field, pressure etc.) offers a unique opportunity to probe the extreme regime (near the transition point) where strong quantum correlations encompass the macroscopic sample as a whole, so called “quantum criticality” [1]. In this regime of strong correlations small perturbations/interactions can stabilize novel forms order or collective fluctuations that otherwise do not exist. One of the theoretically most studied paradigms for quantum criticality is a chain of Ising spins driven by a transverse field to a critical point separating spontaneous magnetic order and paramagnetic phases. We have realized this system experimentally by applying strong magnetic fields to the quasi-one-dimensional Ising ferromagnet CoNb2O6 and have probed via single-crystal inelastic neutron scattering the evolution of the magnetic order and spin excitation spectrum as a function of applied field at mili-Kelvin temperatures [2]. Near the critical point the spin excitations were theoretically predicted nearly two decades ago to have a set of quantum resonances (collective modes of vibration of the interacting spins) with universal ratios between their frequencies reflecting an exceptional mathematical structure of the quantum many-body eigenstates with a “hidden” E8 symmetry governing the physics in the scaling limit. Experiments indeed observed evidence for a spectrum of resonances and the ratio between the frequencies of the two lowest modes approached the "golden ratio" near the critical point, as predicted by field theory. As a second example of novel physics near quantum criticality I will discuss how an amplitude-modulated incommensurate spin-density wave (SDW) order appears near the field-induced critical point in the quasi-1D spin-1/2 XY antiferromagnet Cs2CoCl4. Incommensurate SDWs are very uncommon in magnetic insulators and are not stable zero-temperature ground states at the classical mean-field level, we propose that here such a state is stabilized by the strong quantum fluctuations associated with the proximity to the critical point and the weak frustrated inter-chain couplings.
12/13 PSI - Explorations in Condensed Matter Lecture 14
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 25, 2013

PIRSA:13040060
Condensed Matter
Electronic Liquid Crystalline Phases of Highly Correlated Electronic Systems
April 24, 2013

PIRSA:13040116
Condensed Matter
In one extreme, where the interactions are sufficiently weak compared to the interactions, electrons form a “Fermi liquid” – the state that accounts for the properties of simple metals. In the other extreme, where the interactions are dominant, the electrons form various “Mott” insulating or “Wigner crystalline” phases, often characterized by broken spatial and/or magnetic symmetries. Corresponding charge and/or magnetically ordered insulating phases are common in nature. Between these two extremes lie highly correlated electronic fluids, and correspondingly a host of interesting and perplexing materials, including such diverse systems as the cuprate and iron-based high temperature superconductors, the failed metamagnet Sr3Ru2O7, and a variety of quantum Hall fluids. Some insight into electron fluids in this rich intermediate coupling regime can be obtained from viewing them as partially melted electron solids, rather than as strongly interacting gases. Here, analogies with the liquid crystalline phases of complex classical fluids provide useful guidance for a new approach to this key problem in condensed matter physics.
12/13 PSI - Explorations in Condensed Matter Lecture 13
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 24, 2013

PIRSA:13040059
Condensed Matter
Quantum transport in one dimension: from integrability to many-body localization and topology

Joel Moore University of California, Berkeley
April 23, 2013

PIRSA:13040125
Condensed Matter
Recent advances in analytical theory and numerical methods enable some long-standing questions about transport in one dimension to be answered; these questions are closely related to transport experiments in quasi-1D compounds. The spinless fermion chain with nearest-neighbor interactions at half-filling, or equivalently the XXZ model in zero magnetic field, is an example of an integrable system in which no conventional conserved quantity forces dissipationless transport (Drude weight); we show that there is nevertheless a Drude weight and that at some points its contribution is from a new type of conserved quantity recently constructed by Prosen. Adding an integrability-breaking perturbation leads to a scaling theory of conductivity at low temperature. Adding disorder, we study the question of how Anderson localization is modified by interactions when the system remains fully quantum coherent ("many-body localization"). We find that even weak interactions are a singular perturbation on some quantities: entanglement grows slowly but without limit, suggesting that dynamics in the possible many-body localized phase are glass-like. If time permits, some results on the fractional Luttinger's theorem and the 1D limit of quantum Hall states will be presented.
12/13 PSI - Explorations in Condensed Matter Lecture 12
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 23, 2013

PIRSA:13040058
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 11
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 22, 2013

PIRSA:13040057
Condensed Matter
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

Max Metlitski Massachusetts Institute of Technology (MIT) - Department of Physics
April 10, 2013

PIRSA:13040117
Condensed Matter
In this talk, I will construct a symmetry protected topological phase of bosons in 3d with particle number conservation and time reversal symmetries, which is the direct bosonic analogue of the familiar electron topological insulator. The construction employs a parton decomposition of bosons, followed by condensation of parton-monopole composites. The surface of the resulting state supports a gapped symmetry respecting phase with intrinsic toric code topological order where both e and m anyons carry charge 1=2. It is well-known that one signature of the 3d electron topological insulator is the Witten eect: if the system is coupled to a compact electromagnetic gauge eld, a monopole in the bulk acquires a half-odd-integer polarization charge. I will discuss the corresponding phenomenon for the constructed topological insulator of bosons: a monopole can remain electrically neutral, but its statistics are transmuted from bosonic to fermionic. This \sta- tistical Witten eect" guarantees that the surface is either gapless, symmetry broken or carries an intrinsic topological order.
S=1 spin liquid with fermionic excitations

Maksym Serbyn Massachusetts Institute of Technology (MIT)
March 28, 2013

PIRSA:13030113
Condensed Matter
In the first part of my talk I describe a search for possible quantum spin liquid ground states for spin S=1 Heisenberg models on the triangular lattice which was motivated by recent experiments on Ba3NiSb2O9. We use representation of spin-1 via three flavors of fermionic spinon operators. The ground state where one gapless flavor of spinons with a Fermi surface coexists with d+id topological pairing of the two other flavors can explain available experimental data. Despite the existence of a Fermi surface, this spin liquid state has fully gapped bulk spin excitations. This results in a linear in-temperature specific heat and constant in-plane spin susceptibility, with an unusually high Wilson ratio. Using variational Monte Carlo technique, we show that proposed spin liquid ground state is realized in an SU(3)-invariant model with sufficiently strong ring-exchange terms. In the second part, I consider the physics of the magnetic s=1/2 impurity embedded in a S=1 spin liquid, where all three flavors of spinons have a Fermi surface. The interplay between non-Fermi-liquid behavior induced by a U(1) gauge field coupled to fermions, and a non-Fermi-liquid fixed point in the overscreened Kondo problem is studied using double expansion. The gauge field changes the physical properties of the system at the overscreened Kondo fixed point. Thus, spin-half impurity in such spin liquid can be used to probe the presence of fermionic spinons coupled to the gauge field. References: arXiv:1108.3070, arXiv:1208.3231 and arXiv:1212.5179
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Michael Hermele University of Colorado Boulder
March 26, 2013

PIRSA:13030116
Condensed Matter
Quantum number fractionalization is a remarkable property of topologically ordered states of matter, such as fractional quantum Hall liquids, and quantum spin liquids. For a given type of topological order, there are generally many ways to fractionalize the quantum numbers of a given symmetry. What does it mean to have different types of fractionalization? Are different types of fractionalization a universal property that can be used to distinguish phases of matter? In this talk, I will answer these questions, focusing on a simple class of topologically ordered phases, namely two-dimensional gapped Z2 spin liquids, and I will present a symmetry classification of these phases. I will also discuss efforts in progress to find microscopic models realizing different symmetry classes.

Title	Speaker(s)	Date	Talk Type	Info link
Absence of Pauling's Residual Entropy in Dy2Ti2O	Jan Kycia	2013-04-25	Conference	View details
Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons	Zhihao Hao	2013-04-25	Conference	View details
Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter	Radu Coldea	2013-04-25	Conference	View details
12/13 PSI - Explorations in Condensed Matter Lecture 14	Guifre Vidal, Xiao-Gang Wen	2013-04-25	Course	View details
Electronic Liquid Crystalline Phases of Highly Correlated Electronic Systems		2013-04-24	Scientific Series	View details
12/13 PSI - Explorations in Condensed Matter Lecture 13	Guifre Vidal, Xiao-Gang Wen	2013-04-24	Course	View details
Quantum transport in one dimension: from integrability to many-body localization and topology	Joel Moore	2013-04-23	Scientific Series	View details
12/13 PSI - Explorations in Condensed Matter Lecture 12	Guifre Vidal, Xiao-Gang Wen	2013-04-23	Course	View details
12/13 PSI - Explorations in Condensed Matter Lecture 11	Guifre Vidal, Xiao-Gang Wen	2013-04-22	Course	View details
Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.	Max Metlitski	2013-04-10	Scientific Series	View details
S=1 spin liquid with fermionic excitations	Maksym Serbyn	2013-03-28	Scientific Series	View details
Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions	Michael Hermele	2013-03-26	Scientific Series	View details

Supported by

Format results

Absence of Pauling's Residual Entropy in Dy2Ti2O

Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

12/13 PSI - Explorations in Condensed Matter Lecture 14

Electronic Liquid Crystalline Phases of Highly Correlated Electronic Systems

12/13 PSI - Explorations in Condensed Matter Lecture 13

Quantum transport in one dimension: from integrability to many-body localization and topology

12/13 PSI - Explorations in Condensed Matter Lecture 12

12/13 PSI - Explorations in Condensed Matter Lecture 11

Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

S=1 spin liquid with fermionic excitations

Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions

Absence of Pauling's Residual Entropy in Dy2Ti2O

Spin-1/2 Heisenberg Antiferromagnet on the Kagome Lattice: a Z2 Spin Liquid with Fermionic Spinons

Reaching Experimentally Quantum Criticality: A Playground to Explore Novel Correlated Quantum States of Matter

12/13 PSI - Explorations in Condensed Matter Lecture 14

Electronic Liquid Crystalline Phases of Highly Correlated Electronic Systems

12/13 PSI - Explorations in Condensed Matter Lecture 13

Quantum transport in one dimension: from integrability to many-body localization and topology

12/13 PSI - Explorations in Condensed Matter Lecture 12

12/13 PSI - Explorations in Condensed Matter Lecture 11

Topological insulator of bosons in 3d via dyon condensation and the statistical Witten effect.

S=1 spin liquid with fermionic excitations

Classifying fractionalization: symmetry classification of gapped Z2 spin liquids in two dimensions