Quantum Matter

Quantum matter physics is the branch of physics that studies systems of very large numbers of particles in a condensed state, like solids or liquids. Quantum matter physics wants to answer questions like: why is a material magnetic? Or why is it insulating or conducting? Or new, exciting questions like: what materials are good to make a reliable quantum computer? Can we describe gravity as the behavior of a material? The behavior of a system with many particles is very different from that of its individual particles. We say that the laws of many body physics are emergent or collective. Emergence explains the beauty of physics laws.

Displaying 1021 - 1032 of 1223

Entangled states of quantum matter

Subir Sachdev Harvard University
May 08, 2013

PIRSA:13050038
Condensed Matter
Holographic insights into quantum critical transport: from branes to Bose-Hubbard
May 08, 2013

PIRSA:13050037
Condensed Matter
Thermodynamical Property of Entanglement Entropy for Excited States

Tadashi Takayanagi Yukawa Institute for Theoretical Physics
May 08, 2013

PIRSA:13050034
Condensed Matter
3D topological lattice models with topologically ordered surface states

Fiona Burnell University of Minnesota
May 07, 2013

PIRSA:13050032
Condensed Matter
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Zheng-Cheng Gu Chinese University of Hong Kong
May 07, 2013

PIRSA:13050052
Condensed Matter
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

Erez Berg Weizmann Institute of Science
May 07, 2013

PIRSA:13050029
Condensed Matter
A 3d Boson Topological Insulator and the “Statistical Witten Effect”

Matthew Fisher University of California, Santa Barbara
May 07, 2013

PIRSA:13050028
Condensed Matter
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Baskaran Ganapathy Institute of Mathematical Sciences
April 30, 2013

PIRSA:13040140
Condensed Matter
12/13 PSI - Explorations in Condensed Matter Lecture 15
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 26, 2013

PIRSA:13040061
Condensed Matter

Entangled states of quantum matter

Subir Sachdev Harvard University
May 08, 2013

PIRSA:13050038
Condensed Matter
Theorists have been studying and classifying entanglement in many-particle quantum states for many years. In the past few years, experiments on such states have finally appeared, generating much excitement. I will describe experimental observations on magnetic insulators, ultracold atoms, and high temperature superconductors, and their invigorating influence on our theoretical understanding.
Holographic insights into quantum critical transport: from branes to Bose-Hubbard
May 08, 2013

PIRSA:13050037
Condensed Matter
We discuss the general features of charge transport of quantum critical points described by CFTs in 2+1D. Our main tool is the AdS/CFT correspondence, but we will make connections to standard field theory results and to recent quantum Monte Carlo data. We emphasize the importance of poles and zeros of the response functions. In the holographic setting, these are the discrete quasinormal modes of a black hole/brane; they map to the excitations of the CFT. We further describe the role of particle-vortex or S-duality on the conductivity, which is argued to obey two powerful sum rules.
References (with S. Sachdev): arXiv:1210.4166 (PRB 12); arXiv:1302.0847 (PRB 13)
Thermodynamical Property of Entanglement Entropy for Excited States

Tadashi Takayanagi Yukawa Institute for Theoretical Physics
May 08, 2013

PIRSA:13050034
Condensed Matter
We will point out that there is a universal thermodynamical property of entanglement entropy for excited states. We will derive this by using the AdS/CFT correspondence in any dimension. We will also directly confirm this property from direct field theoretic calculations in two dimensions. We will define a new quantity called entanglement density by taking derivatives of entanglement entropy with respect to the shape of subsystem. We will show that this quantity coincides with the energy density by taking the small subsystem limit and show that this is another equivalent statement of the thermodynamical property.
3D topological lattice models with topologically ordered surface states

Fiona Burnell University of Minnesota
May 07, 2013

PIRSA:13050032
Condensed Matter
I will discuss a family of solvable 3D lattice models that have a ``trivial" bulk, in which all excitations are confined, but exhibit topologically ordered surface states. I will discuss perturbations to these models that can drive a phase transition in which some of these excitations become deconfined, driving the system into a phase with bulk topological order.
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Zheng-Cheng Gu Chinese University of Hong Kong
May 07, 2013

PIRSA:13050052
Condensed Matter
The existence of three generations of neutrinos and their mass mixing is a deep mystery of our universe. On the other hand, Majorana's elegant work on the real solution of Dirac equation predicted the existence of Majorana particles in our nature, unfortunately, these Majorana particles have never been observed. In this talk, I will begin with a simple 1D condensed matter model which realizes a T^2=-1 time reversal symmetry protected superconductors and then discuss the physical property of its boundary Majorana zero modes. It is shown that these Majorana zero modes realize a T^4=-1 time reversal doubelets and carry 1/4 spin. Such a simple observation motivates us to revisit the CPT symmetry of those ghost particles--neutrinos by assuming that they are Majorana zero modes. Interestingly, we find that a topological Majorana particle will realize a P^4=-1 parity symmetry as well. It even realizes a nontrivial C^4=-1 charge conjugation symmetry, which is a big surprise from a usual perspective that the charge conjugation symmetry for a Majorana particle is trivial. Indeed, such a C^4=-1 charge conjugation symmetry is a Z_2 gauge symmetry and its spontaneously breaking leads to the origin of neutrino mass. We further attribute the origin of three generations of neutrinos to three distinguishable types of topological Majorana zero modes protected by CPT symmetry. Such an assumption leads to an S3 symmetry in the generation space and uniquely determines the mass mixing matrix with no adjustable parameters! In the absence of CP violation, we derive \theta_12=32degree, \theta_23=45degree and \theta_13=0degree, which is intrinsically closed to the current experimental results. We further predict an exact mass ratio of the three mass eigenstate with m_1/m_3~m_2/m_3=3/\sqrt{5}.
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

Erez Berg Weizmann Institute of Science
May 07, 2013

PIRSA:13050029
Condensed Matter
We study the non-abelian statistics characterizing systems where counter-propagating gapless modes on the edges of fractional quantum Hall states are gapped by proximity-coupling to superconductors and ferromagnets. The most transparent example is that of a fractional quantum spin Hall state, in which electrons of one spin direction occupy a fractional quantum Hall state of $\nu= 1/m$, while electrons of the opposite spin occupy a similar state with $\nu = -1/m$. However, we also propose other examples of such systems, which are easier to realize experimentally. We find that each interface between a region on the edge coupled to a superconductor and a region coupled to a ferromagnet corresponds to a non-abelian anyon of quantum dimension $\sqrt{2m}$. We calculate the unitary transformations that are associated with braiding of these anyons, and show that they are able to realize a richer set of non-abelian representations of the braid group than the set realized by non-abelian anyons based on Majorana fermions. We carry out this calculation both explicitly and by applying general considerations. Finally, we show that topological manipulations with these anyons cannot realize universal quantum computation.
A 3d Boson Topological Insulator and the “Statistical Witten Effect”

Matthew Fisher University of California, Santa Barbara
May 07, 2013

PIRSA:13050028
Condensed Matter
Electron topological insulators are members of a broad class of “symmetry protected topological” (SPT) phases of fermions and bosons which possess distinctive surface behavior protected by bulk symmetries. For 1d and 2d SPT’s the surfaces are either gapless or symmetry broken, while in 3d, gapped symmetry-respecting surfaces with (intrinsic) 2d topological order are also possible. The electromagnetic response of (some) SPT’s can provide an important characterization, as illustrated by the Witten effect in 3d electron topological insulators. Using a 3d parton-gauge theory construction, we have recently developed a dyon condensation approach to access exotic new phases including some 3d bosonic SPT’s. A bosonic SPT with both time-reversal and charge conservation symmetries, is thereby obtained, a phase which supports a gapped, symmetry-unbroken 2d surface with topological order - a toric code with charge one-half anyons. The 3d electromagnetic response of this bosonic SPT phase is quite remarkable - an external magnetic monopole can remain charge neutral, but is statistically transmuted becoming a fermion - a “statistical Witten effect” that characterizes the phase.
Emergent Fermionic Strings in Bosonic He4 Crystal

Baskaran Ganapathy Institute of Mathematical Sciences
May 06, 2013

PIRSA:13050025
Condensed Matter
Large zero point motion of light atoms in solid Helium 4 leads to several anomalous properties, including a supersolid type behavior. We suggest an `anisotropic quantum melted' atom density wave model for solid He4 with hcp symmetry. Here, atoms preferentially quantum melt along the c-axis and maintain self organized crystallinity and confined dynamics along ab-plane. This leads to profound consequences: i) statistics transmutation of He4 atoms into fermions for c-axis dynamics, arising from restricted one dimensional motion and hard core repulsion, ii) resulting `fermionic strings' undergo Peierls instability (an atom density wave formation) in a staggered fashion and help regain the original hcp crystal symmetry, iii) `particle-hole' type excitations iv) emergence of `confined' `half atom' domain wall excitations, and so on. Known anomalies of solid He4 gets a natural qualitative explanation in the present scenario.
Quantum spin liquid phases in the absence of spin-rotation symmetry

Yong-Baek Kim University of Toronto
May 06, 2013

PIRSA:13050023
Condensed Matter
We investigate possible quantum spin liquid phases in the presence of a variety of spin-rotational-symmetry breaking perturbations. Projective symmetry group analysis on slave-particle representations is used to understand possible spin liquid phases on the Kagome lattice. The results of this analysis are used to make connections to the exiting and future experiments on Herbertsmithites. Applications to other systems are also discussed.
3d boson topological insulators and quantum spin liquids

Senthil Todadri Massachusetts Institute of Technology (MIT) - Department of Physics
May 06, 2013

PIRSA:13050021
Condensed Matter
I will discuss recent work on 3d Symmetry Protected Topological (SPT) phases of bosonic systems, and their implications for understanding the more exotic quantum spin liquid phases. First I will describe various characterizations of these 3d SPT phases, in particular their surface effective theories and (when applicable) bulk electromagnetic response. Next I will show how this understanding leads to several new insights into the theory of both 2d and 3d quantum spin liquids. Finally I will provide an explicit construction of several 3d SPT phases in a system of `coupled layers'. This includes a 3d SPT state that is beyond the existing cohomology classification of such states.
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

Baskaran Ganapathy Institute of Mathematical Sciences
April 30, 2013

PIRSA:13040140
Condensed Matter
Utilizing a variety and also constraints offered by quantum and solid state chemistry, we discuss possibilities of unconventional quantum magnetism and superconductivity in doped 3 dimensional Mott insulators. Some of the possibilities are quantum spin liquid states having pseudo fermi surface coexisting with long range magnetic order, 3 dimensional emergent gauge fields and unconventional superconducting order parameter symmetry. We present a few realistic models to illustrate this and use our theory to understand anomalous behavior of certain double perovskite compounds.
12/13 PSI - Explorations in Condensed Matter Lecture 15
- Guifre Vidal Alphabet (United States)
- Xiao-Gang Wen Massachusetts Institute of Technology (MIT) - Department of Physics
April 26, 2013

PIRSA:13040061
Condensed Matter

Title	Speaker(s)	Date	Talk Type	Info link
Entangled states of quantum matter	Subir Sachdev	2013-05-08	Scientific Series	View details
Holographic insights into quantum critical transport: from branes to Bose-Hubbard		2013-05-08	Conference	View details
Thermodynamical Property of Entanglement Entropy for Excited States	Tadashi Takayanagi	2013-05-08	Conference	View details
3D topological lattice models with topologically ordered surface states	Fiona Burnell	2013-05-07	Conference	View details
Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing	Zheng-Cheng Gu	2013-05-07	Conference	View details
Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states	Erez Berg	2013-05-07	Conference	View details
A 3d Boson Topological Insulator and the “Statistical Witten Effect”	Matthew Fisher	2013-05-07	Conference	View details
Emergent Fermionic Strings in Bosonic He4 Crystal	Baskaran Ganapathy	2013-05-06	Conference	View details
Quantum spin liquid phases in the absence of spin-rotation symmetry	Yong-Baek Kim	2013-05-06	Conference	View details
3d boson topological insulators and quantum spin liquids	Senthil Todadri	2013-05-06	Conference	View details
Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators	Baskaran Ganapathy	2013-04-30	Scientific Series	View details
12/13 PSI - Explorations in Condensed Matter Lecture 15	Guifre Vidal, Xiao-Gang Wen	2013-04-26	Course	View details

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Entangled states of quantum matter

Holographic insights into quantum critical transport: from branes to Bose-Hubbard

Thermodynamical Property of Entanglement Entropy for Excited States

3D topological lattice models with topologically ordered surface states

Majorana Ghosts: From topological superconductor to the origin of neutrino mass, three generations and their mass mixing

Fractionalizing Majorana fermions: non-abelian statistics on the edges of abelian quantum Hall states

A 3d Boson Topological Insulator and the “Statistical Witten Effect”

Emergent Fermionic Strings in Bosonic He4 Crystal

Quantum spin liquid phases in the absence of spin-rotation symmetry

3d boson topological insulators and quantum spin liquids

Unconventional Magnetism and Superconductivity in 3 Dimensional Doped Mott Insulators

12/13 PSI - Explorations in Condensed Matter Lecture 15