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Computational methods for finite tem...

Stoudenmire, Edwin Miles.

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Computational methods for finite temperature quantum magnets.

Record Type:	Language materials, printed : Monograph/item
Title/Author:	Computational methods for finite temperature quantum magnets./
Author:	Stoudenmire, Edwin Miles.
Description:	170 p.
Notes:	Source: Dissertation Abstracts International, Volume: 71-10, Section: B, page: .
Contained By:	Dissertation Abstracts International71-10B.
Subject:	Physics, Quantum. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3422503
ISBN:	9781124218236

Computational methods for finite temperature quantum magnets.
Stoudenmire, Edwin Miles.

Computational methods for finite temperature quantum magnets. - 170 p.

Source: Dissertation Abstracts International, Volume: 71-10, Section: B, page: .

Thesis (Ph.D.)--University of California, Santa Barbara, 2010.

Quantum spin models are of great interest because they describe the behavior of real magnetic materials and provide a simple context for understanding exotic quantum phases. Experimental results on the triangular lattice antiferromagnet NiGa2S4 in particular have motivated the study of S = 1 models having strong biquadratic interactions that favor a spin nematic ground state. We describe a scenario where the presence of such interactions in NiGa2S4 could be responsible for tuning it into the vicinity of a zero temperature critical point such that two distinct temperature scales emerge in its thermodynamic properties. We also observe that the likely presence of strong third-neighbor exchange interactions in this material leads to a finite temperature phase transition into a classical spin disordered phase that breaks lattice rotational symmetry.

ISBN: 9781124218236Subjects--Topical Terms:

1671062
Physics, Quantum.

Computational methods for finite temperature quantum magnets.
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020 $a 9781124218236
035 $a (UMI)AAI3422503
035 $a AAI3422503
040 $a UMI $c UMI
100 1 $a Stoudenmire, Edwin Miles. $3 1671082
245 1 0 $a Computational methods for finite temperature quantum magnets.
300 $a 170 p.
500 $a Source: Dissertation Abstracts International, Volume: 71-10, Section: B, page: .
500 $a Adviser: Leon Balents.
502 $a Thesis (Ph.D.)--University of California, Santa Barbara, 2010.
520 $a Quantum spin models are of great interest because they describe the behavior of real magnetic materials and provide a simple context for understanding exotic quantum phases. Experimental results on the triangular lattice antiferromagnet NiGa2S4 in particular have motivated the study of S = 1 models having strong biquadratic interactions that favor a spin nematic ground state. We describe a scenario where the presence of such interactions in NiGa2S4 could be responsible for tuning it into the vicinity of a zero temperature critical point such that two distinct temperature scales emerge in its thermodynamic properties. We also observe that the likely presence of strong third-neighbor exchange interactions in this material leads to a finite temperature phase transition into a classical spin disordered phase that breaks lattice rotational symmetry.
520 $a To confirm these predictions, we devise an approach in which the model is treated in a semi-classical approximation amenable to Monte Carlo simulations. Unlike a standard classical approximation, our method retains all of the symmetries of the quantum Hamiltonian and succeeds in correctly capturing the effects of biquadratic interactions. However, it is not able to make quantitatively accurate predictions. In order to address this shortcoming, we turn to a second method that is able to fully treat both quantum and classical thermal effects.
520 $a In this method, thermal averages are computed by sampling a set of wave-functions known as minimally entangled typical thermal states, or METTS. We describe each step of the sampling process in detail and present efficient algorithms for working with matrix product states and matrix product operators. The METTS themselves can be studied to observe characteristic order and excitations of a system, and their properties reveal that they make an especially efficient basis for sampling. Finally, we explore the extent to which the average entanglement of a METTS ensemble is minimal. Future possibilities for both the semi-classical and METTS methods are discussed.
590 $a School code: 0035.
650 4 $a Physics, Quantum. $3 1671062
650 4 $a Physics, Condensed Matter. $3 1018743
690 $a 0599
690 $a 0611
710 2 $a University of California, Santa Barbara. $b Physics. $3 1020469
773 0 $t Dissertation Abstracts International $g 71-10B.
790 1 0 $a Balents, Leon, $e advisor
790 1 0 $a Fisher, Matthew $e committee member
790 1 0 $a Seshadri, Ram $e committee member
790 $a 0035
791 $a Ph.D.
792 $a 2010
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3422503