1.
The quantum spin Hall state has which of the following?
Correct Answer
D. All of the above
Explanation
The quantum spin Hall state exhibits all of the mentioned characteristics. It is a state of matter that occurs in certain semiconductors, where the charge-Hall conductance vanishes and the spin-Hall conductance is quantized. This means that the flow of charge and spin currents in the material is highly controlled and predictable, making it a promising candidate for applications in spintronics and quantum computing.
2.
Which of the following is false?
Correct Answer
C. The quantum spin Hall state breaks charge conservation symmetry
Explanation
The quantum spin Hall state of matter does not break charge conservation symmetry. Charge conservation symmetry refers to the principle that the total electric charge in a closed system remains constant over time. The quantum spin Hall state, on the other hand, is a state of matter that exhibits topological insulating behavior in two dimensions, where the edge states are protected by time-reversal symmetry. It does not involve any violation of charge conservation symmetry.
3.
The first proposal for the existence of a quantum spin Hall state was developed by who?
Correct Answer
E. A and C
Explanation
The correct answer is A and C. Charles Kane and Gene Mele both independently proposed the existence of a quantum spin Hall state. Their work, published in 2005, introduced the concept of a topological insulator, a material that behaves as an insulator in its interior but conducts electricity on its surface due to the presence of protected conducting states. This groundbreaking research laid the foundation for further studies and experiments in the field of topological insulators and quantum spin Hall effect.
4.
According to the two copies of the Haldane model, the spin-up electron exhibits which of the following?
Correct Answer
A. A chiral integer quantum Hall effect
Explanation
The correct answer is A chiral integer quantum Hall effect. The Haldane model is a theoretical model used to study the quantum Hall effect. In the quantum Hall effect, when a magnetic field is applied perpendicular to a two-dimensional electron gas, the electrons form Landau levels and exhibit quantized Hall conductance. The chiral integer quantum Hall effect refers to the situation where the Hall conductance is quantized to integer values and the edge states of the system propagate in one direction only. This is consistent with the behavior of the spin-up electron in the Haldane model.
5.
A relativistic version of the quantum spin Hall effect was introduced when?
Correct Answer
B. 1990s
Explanation
In the 1990s, a relativistic version of the quantum spin Hall effect was introduced. This suggests that the correct answer is the 1990s.
6.
A quantum spin Hall model was proposed by which of the given options?
Correct Answer
A. Bernevig
Explanation
The correct answer is Bernevig. Bernevig, along with his colleagues, proposed the quantum spin Hall model. This model describes a new state of matter known as a topological insulator, where the bulk of the material is an insulator, but its edges or surfaces conduct electricity. The model has been influential in the field of condensed matter physics and has led to further research and discoveries in topological materials.
7.
After the introduction of spin-up spin-down scattering, which of the following was realized?
Correct Answer
C. That the quantum spin Hall state remained non-trivial
Explanation
After the introduction of spin-up spin-down scattering, it was realized that the quantum spin Hall state remained non-trivial. This means that the scattering did not cause a change in the nature of the quantum spin Hall state, indicating that it still retained its unique properties.
8.
Which of the following was proved by stability studies of the edge liquid through which conduction occurs in the quantum spin Hall state?
Correct Answer
C. A & B
Explanation
The correct answer, A & B, suggests that stability studies of the edge liquid in the quantum spin Hall state have proven two things. First, the non-trivial state is robust to interactions, meaning that it remains stable even in the presence of external forces or interactions with other particles. Second, the non-trivial state is also robust to extra spin-orbit coupling terms that mix spin-up and spin-down electrons, indicating that it can withstand perturbations that could potentially disrupt its properties.
9.
Time reversal symmetry is not needed to protect quantum spin Hall state.
Is the above statement true or false?
Correct Answer
A. Yes, it's true
Explanation
This statement is true. Time reversal symmetry is not necessary to protect the quantum spin Hall state. The quantum spin Hall state is a topological insulator that exhibits a non-trivial band structure and protected edge states. These edge states are protected by the presence of a bulk energy gap and the conservation of certain symmetries, such as particle-hole symmetry and time reversal symmetry. However, recent research has shown that certain systems can still exhibit a quantum spin Hall state even in the absence of time reversal symmetry, as long as other symmetries are present to protect the edge states.
10.
Which of the following is true?
Correct Answer
A. Topological insulator and quantum spin Hall state are different states of matter
Explanation
Topological insulator and quantum spin Hall state are different states of matter. This is because topological insulators are materials that are insulating in the bulk but conductive on the surface, while quantum spin Hall states are a specific type of topological insulator that exhibit a quantized spin Hall effect. Symmetry-protected topological order is another concept related to topological insulators, but it is not the same as a quantum spin Hall state. Zhang and Haldane did propose the first quantum spin Hall model, but this does not imply that topological insulators and quantum spin Hall states are the same.