Random generated vector in C++ is not changing values

My class contains some vector matrix of type:

typedef std::vector<double> MyArray;
typedef std::vector<MyArray> MyMatrix;

Class has an update() method, and on each call it should generate a new random matrix, and old place in std::map<double, MyMatrix, std::greater<double>> rankedMyMatrix_;.

Update method looks approximately like this:

void MyClass::update(...){
     ...
     this->generateMyMatrix();  // Generates new random currentMyMatrix_
     ...
     rankedMyMatrix_.insert({matrixRank_, currentMyMatrix_});
     ...
}

Method generateMyMatrix() looks like this:

void MyClass::generateMyMatrix(){
     std::random_device rd;
     std::mt19937 mt(rd());
     std::uniform_real_distribution<double> dist(-1, 1);
     for (int i = 0; i < noMotors_; i++) {
         MyArray array(MaxArraySamples, 0);
         for (int j = 0; j < MaxArraySamples; j = j + steps) {
             array[j] = dist(mt);
         }
     currentMyMatrix_.push_back(array);
     }
}

Trouble is that on each push to rankedMyMatrix_ map, on new update() it generates same matrix. Or it does not write to it? Probably I am missing something here, so any help would be appreciated.