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Quantum Spin Liquid State


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#1 hazelm

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Posted 23 January 2019 - 07:10 AM

A perovskite-related metal oxide exhibits a quantum liquid state - a long sought and unusual state of matter.

 

https://www.scienced...p Science News)

 



#2 exchemist

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Posted 23 January 2019 - 09:06 AM

A perovskite-related metal oxide exhibits a quantum liquid state - a long sought and unusual state of matter.

 

https://www.scienced...p Science News)

Now you're just testing! 

 

Tb 3+ seems to have potential for unusual magnetic properties as it has 8 electrons in f orbitals. As f orbitals come in sets of 7, each one of which can accept a pair of electrons with opposite spins, in this ion only 2 electrons will have their spins paired and cancelling. Unpaired electron spins give rise to magnetic moments. 

 

Furthermore, as each electron in an f orbital has 2 units of orbital angular momentum, there will be magnetic moments from this, as well as from electron spin. So some fairly exotic magnetic behaviour should be expected. It's a heavy atom so j-j coupling should apply, i.e. the spin and orbital moment of each electron will combine to give a total j moment per electron, and then these totals will combine to give the total for the whole atom. How it works out in detail I do not know, but I imagine there will be a lot of different spatial orientations of the magnetic moment possible. 

 

This "quantum liquid" (which I had never previously heard of) appears to be a state in which there is no alignment of these various magnetic moments from one atom to the next- apparently even at absolute zero, according to the paper. (Dubbelsox will hate that :) )  

 

This lack of alignment is unheard of, as normally the magnetic moment of one atom creates a field that causes the neighbours to line up with or against it. 

 

I can't follow the details but whatever it is, it will be something related to all this. That's about the best I can do, without a lot more work.


Edited by exchemist, 23 January 2019 - 09:08 AM.


#3 hazelm

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Posted 23 January 2019 - 09:36 AM

Now you're just testing! 

 

Tb 3+ seems to have potential for unusual magnetic properties as it has 8 electrons in f orbitals. As f orbitals come in sets of 7, each one of which can accept a pair of electrons with opposite spins, in this ion only 2 electrons will have their spins paired and cancelling. Unpaired electron spins give rise to magnetic moments. 

 

Furthermore, as each electron in an f orbital has 2 units of orbital angular momentum, there will be magnetic moments from this, as well as from electron spin. So some fairly exotic magnetic behaviour should be expected. It's a heavy atom so j-j coupling should apply, i.e. the spin and orbital moment of each electron will combine to give a total j moment per electron, and then these totals will combine to give the total for the whole atom. How it works out in detail I do not know, but I imagine there will be a lot of different spatial orientations of the magnetic moment possible. 

 

This "quantum liquid" (which I had never previously heard of) appears to be a state in which there is no alignment of these various magnetic moments from one atom to the next- apparently even at absolute zero, according to the paper. (Dubbelsox will hate that :) )  

 

This lack of alignment is unheard of, as normally the magnetic moment of one atom creates a field that causes the neighbours to line up with or against it. 

 

I can't follow the details but whatever it is, it will be something related to all this. That's about the best I can do, without a lot more work.

Hoping. This is the only place where I have ever read of a liquid state in quantum or classical physics.  I'm hoping to get something out of it.  Always grasping for something new.  It is an interesting universe but hard to keep up with.



#4 exchemist

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Posted 24 January 2019 - 01:57 AM

Hoping. This is the only place where I have ever read of a liquid state in quantum or classical physics.  I'm hoping to get something out of it.  Always grasping for something new.  It is an interesting universe but hard to keep up with.

The "quantum liquid" description of this strikes me as a bit obscurantist - never a good thing in science. All they mean is that the magnetic moments are randomly orientated at all temperatures, unlike just about any other material in which the atoms have magnetic moments. The analogy with a liquid will be that in a liquid there is a disordered arrangement of the molecules.

 

In a liquid, the molecules are also in motion of course, so the disordered arrangement is not fixed, but constantly changing in a random way. I could not see from the link whether the magnetic moments in this material are also constantly changing, or whether they are fixed. If the latter, they really ought to call it a "quantum glass", I suppose.  


Edited by exchemist, 24 January 2019 - 08:16 AM.


#5 Flummoxed

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Posted 24 January 2019 - 06:48 AM

A perovskite-related metal oxide exhibits a quantum liquid state - a long sought and unusual state of matter.

 

https://www.scienced...p Science News)

 

I think this is the paper they are referring too https://arxiv.org/ft.../1806.08215.pdf

 

"Spin liquid ground states are predicted to arise within several distinct scenarios in condensed matter physics. The observation of these disordered magnetic states is particularly pervasive amongst a class of materials known as frustrated magnets, in which the competition between various magnetic exchange interactions prevents the system from adopting long-range magnetic order at low temperatures. Spin liquids continue to be of great interest due to their exotic nature and the possibility that they may support fractionalised excitations, such as Majorana fermions. Systems that allow for such phenomena are not only fascinating from a fundamental perspective but may also be practically significant in future technologies based on quantum computation. Here we show that the underlying antiferromagnetic sublattice in TbInO3 undergoes a crystal field induced triangular-to-honeycomb dilution at low temperatures. The absence of a conventional magnetic ordering transition at the lowest measurable temperatures indicates that another critical mechanism must govern in the ground state selection of TbInO3. We propose that anisotropic exchange interactions – mediated through strong spin-orbit coupling on the emergent honeycomb lattice of TbInO3 – give rise to a highly frustrated spin liquid."



#6 hazelm

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Posted 24 January 2019 - 06:57 AM

The "quantum liquid" description of this strikes me as a bit obscurantist - never a good thing in science. All they mean is that the magnetic moments are randomly orientated at all temperatures, unlike just about any other material with which the atoms have magnetic moments. The analogy with a liquid will be that in a liquid there is a disordered arrangement of the molecules.

 

In a liquid, the molecules are also in motion of course, so the disordered arrangement is not fixed, but constantly changing in a random way. I could not see from the link whether the magnetic moments in this material are also constantly changing, or whether they are fixed. If the latter, they really ought to call it a "quantum glass", I suppose.  

Sometimes - more often than I like, actually - I wonder about the discoveries that scientists report.  But I keep digging to see what I am missing - if anything.  Where do they fit into the grand scheme of what we are putting together as the story of our universe?  That is what I am wondering about this liquid.  Pre-big bang or no?  Another possible source of matter? A process of organizing/arranging all of those quantum particles - some of which we know exist and some which we think exist?  I am just looking for a purpose and place for this liquid with magnetic properties that seem not to follow the rules.  

 

(exchemist):  "This lack of alignment is unheard of, as normally the magnetic moment of one atom creates a field that causes the neighbours to line up with or against it."

 

Can it create such a field if the moments are at random?  Is there a plan in the process of forming the whole quantum field?

 

I don't make sense? 



#7 hazelm

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Posted 24 January 2019 - 07:00 AM

I think this is the paper they are referring too https://arxiv.org/ft.../1806.08215.pdf

 

"Spin liquid ground states are predicted to arise within several distinct scenarios in condensed matter physics. The observation of these disordered magnetic states is particularly pervasive amongst a class of materials known as frustrated magnets, in which the competition between various magnetic exchange interactions prevents the system from adopting long-range magnetic order at low temperatures. Spin liquids continue to be of great interest due to their exotic nature and the possibility that they may support fractionalised excitations, such as Majorana fermions. Systems that allow for such phenomena are not only fascinating from a fundamental perspective but may also be practically significant in future technologies based on quantum computation. Here we show that the underlying antiferromagnetic sublattice in TbInO3 undergoes a crystal field induced triangular-to-honeycomb dilution at low temperatures. The absence of a conventional magnetic ordering transition at the lowest measurable temperatures indicates that another critical mechanism must govern in the ground state selection of TbInO3. We propose that anisotropic exchange interactions – mediated through strong spin-orbit coupling on the emergent honeycomb lattice of TbInO3 – give rise to a highly frustrated spin liquid."

I wish I had seen this before I opened my mouth. :-(    Thank you, Flummoxed.



#8 Flummoxed

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Posted 24 January 2019 - 07:52 AM

I wish I had seen this before I opened my mouth. :-(    Thank you, Flummoxed.

 

No worries, exchemist pretty much covered it anyway. 

 

When I want a slightly more technical paper I always start by including arxiv in the search string. You get all the good stuff, and some not so good  :innocent:



#9 exchemist

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Posted 24 January 2019 - 08:29 AM

Sometimes - more often than I like, actually - I wonder about the discoveries that scientists report.  But I keep digging to see what I am missing - if anything.  Where do they fit into the grand scheme of what we are putting together as the story of our universe?  That is what I am wondering about this liquid.  Pre-big bang or no?  Another possible source of matter? A process of organizing/arranging all of those quantum particles - some of which we know exist and some which we think exist?  I am just looking for a purpose and place for this liquid with magnetic properties that seem not to follow the rules.  

 

(exchemist):  "This lack of alignment is unheard of, as normally the magnetic moment of one atom creates a field that causes the neighbours to line up with or against it."

 

Can it create such a field if the moments are at random?  Is there a plan in the process of forming the whole quantum field?

 

I don't make sense? 

This research, like most, is just a curiosity at present. It is interesting because it is counterintuitive: one expects electron magnetic moments to align, at least a low temperatures. This one apparently doesn't.  

 

As to where it fits into the "story of our universe", that is rather a grand expectation. But it pushes the boundaries of known chemical physics a bit further. The phenomenon was predicted, so it does not shake the foundations of any theory, but it is satisfying to have found a material that confirms the prediction. QM passes yet another test, in fact!  



#10 exchemist

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Posted 24 January 2019 - 08:35 AM

I think this is the paper they are referring too https://arxiv.org/ft.../1806.08215.pdf

 

"Spin liquid ground states are predicted to arise within several distinct scenarios in condensed matter physics. The observation of these disordered magnetic states is particularly pervasive amongst a class of materials known as frustrated magnets, in which the competition between various magnetic exchange interactions prevents the system from adopting long-range magnetic order at low temperatures. Spin liquids continue to be of great interest due to their exotic nature and the possibility that they may support fractionalised excitations, such as Majorana fermions. Systems that allow for such phenomena are not only fascinating from a fundamental perspective but may also be practically significant in future technologies based on quantum computation. Here we show that the underlying antiferromagnetic sublattice in TbInO3 undergoes a crystal field induced triangular-to-honeycomb dilution at low temperatures. The absence of a conventional magnetic ordering transition at the lowest measurable temperatures indicates that another critical mechanism must govern in the ground state selection of TbInO3. We propose that anisotropic exchange interactions – mediated through strong spin-orbit coupling on the emergent honeycomb lattice of TbInO3 – give rise to a highly frustrated spin liquid."

Thanks for the link. I was frustrated that they did not go into the electronic structure of the Tb3+ ion and how this is modified by crystal field theory. They evidently assume that their target readership will already know this. I'm afraid I cannot work it out for myself. 



#11 GAHD

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Posted 24 January 2019 - 08:43 PM

Thanks for the link. I was frustrated that they did not go into the electronic structure of the Tb3+ ion and how this is modified by crystal field theory. They evidently assume that their target readership will already know this. I'm afraid I cannot work it out for myself. 

Just by the titles, I'd think references 2 and 3 might be a good place to look for that?